What Is Parthenocarpy: Information And Examples Of Parthenocarpy

By: Bonnie L. Grant, Certified Urban Agriculturist

What do bananas and figs have in common? They both develop without fertilization and produce no viable seeds. This situation of parthenocarpy in plants can occur in two types, vegetative and stimulative parthenocarpy.

Parthenocarpy in plants is a relatively unusual condition but it does occur in some of our most common fruit. What is parthenocarpy? This circumstance occurs when the ovary of a flower develops into a fruit without fertilization. The result is a seedless fruit. Read on to discover what causes parthenocarpy.

What is Parthenocarpy?

The short answer is seedless fruit. What causes parthenocarpy? The word comes from Greek, meaning virgin fruit. As a rule, flowers need to be pollinated and fertilized to create fruit. In some species of plants, a different method has developed, requiring either no fertilization or no fertilization and no pollination.

Pollination is done through insects or wind and spread pollen to the stigma of a flower. The resulting action promotes fertilization which allows a plant to develop seeds. So how does parthenocarpy work and in what instances is it useful?

Examples of Parthenocarpy

In cultivated plants, parthenocarpy is introduced with plant hormones such as gibberellic acid. It causes ovaries to mature without fertilization and produces bigger fruits. The process is being introduced to all kinds of crops from squash to cucumber and more.

It is also a natural process as in the case of bananas. Bananas are sterile and develop no viable ovaries. They do not produce seeds, which mean they must propagate vegetatively. Pineapples and figs are also examples of parthenocarpy which occur naturally.

How Does Parthenocarpy Work?

Vegetative parthenocarpy in plants, like pear and fig, take place without pollination. As we know, pollination leads to fertilization, so in the absence of pollination, no seeds can form.

Stimulative parthenocarpy is a process where pollination is required but no fertilization takes place. It occurs when a wasp inserts its ovipositor into the ovary of a flower. It can also be simulated by blowing air or growth hormones into the unisexual flowers found inside something called a syconium. The syconium is basically the flask-shaped structure lined with the unisexual flowers.

Growth regulating hormones, when used on crops, also halt the fertilization process. In some crop plants, this also occurs due to genome manipulation.

Is Parthenocarpy Beneficial?

Parthenocarpy allows the grower to keep insect pests from his crop without chemicals. This is because no pollinating insect is required for fruit formation so the plants can be covered to prevent the bad insects from attacking the crop.

In the world of organic production, this is a significant improvement from the use of even organic pesticides and improves crop yield and health. Fruits and vegetables are bigger, the growth hormones introduced are natural and the results are easier to achieve and more healthful.

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Parthenocarpy is the ability to develop fruits without pollination (apomixis excluded). According to Pike and Peterson, 108 this character is controlled by an incompletely dominant gene Pc. De Ponti and Garretsen 114 explained the inheritance of parthenocarpy by three independent, isomeric major genes with additive action, together with a non-allelic interaction of the homozygote – heterozygote type. Indications have been found for linkages between genes that govern parthenocarpy femaleness and the spined/hairy fruit character. De Ponti 109 discussed the correlation between several selection criteria and the possibilities of preselection of young plants.

Almost all slicing cucumber varieties cultivated in greenhouses in western Europe are parthenocarpic, and parthenocarpic pickling cucumber varieties are also on the market. In Germany the use of parthenocarpic varieties in production for the processing industry is a major part of the total cultivation area of pickling cucumber. Parthenocarpic fruit setting results in an earlier and much more regular production rhythm. 167 Parthenocarpy circumvents the inhibitory effect of seed formation on subsequent fruit development. Parthenocarpy must be combined with constant femaleness, because the fruits formed after fertilization in genetic parthenocarpic varieties become misshapen, are of no economical value and lead to loss of production. It is possible to induce artificially parthenocarpic fruit set by treatment with morphactin (chlorfluorenol). 125

Tomatos won't set fruit

I have a reader who says his tomato's won't set fruit.
The flowers dry up and fall off. I've never encountered this problem, any thoughts?
I have no information as to the variety or anything else.

THere are a couple of reasons for blossom drop.

The two most common reasons are that the temps are too high for too long in which case the pollen is destroyed.

Same story if the humidity is too high for too long in which case pollen clumps and is much less effective or not at all. Rainy weather, humidity high, a common cause.

Growing in too rich soil or container mixes the same or using too much fertilizer can prevent blossoms from forming as well as blossoms that do appar from setting fruit.

If I were you I'd ask how many plants out there, growing inground or in containers and of those being grown are ALL showing Blossom Drop or just some.

Regardless, there's nothing to be done b'c it's usually weather related and no time to alter soil or fertilizer applications now. The blossom cycle is about three weeks so all is not lost.

I'm having that problem. Our weather goes from triple digits to cold and rainy! I have some in wine barrels and some in the ground.. they all have yet to set any fruit. and they are waist high.. :(

Yesterday we had a full day of cold rainy blustery weather.. which is insane for us. This is the 4th time on record since the 1800s we got rain on June 28th!! Our summers are changing drastically here.. I thought last year was a freak year, but it's worse this year.

I live in the San Joaquin Valley, and it used to be every year the "tomato trucks" would just swarm the entire area every year. All the on ramps and off ramps to the freeways would be sprinkled with tomatoes. I think I saw a total of 2 tomato trucks in the last couple years.

I have the common hybrids in a wine barrel and they are loaded with tomatoes.

I have a Belgium Giant in a wine barrel, it blooms fine, but no fruit. I also have 2 Belgium Giants in the ground, same thing, plant is huge, plenty of blooms, not one fruit.

There is another person in CA that is asking the same thing.. Heirlooms are not setting fruit.

I've tried shaking the plant, paintbrush blooms, more water, less water, more humidity, less, I fertilize with Fish emulsion and that's it. Just can't figure this out!

There is another person in CA that is asking the same thing.. Heirlooms are not setting fruit.

ZZ, the conditions that lead to blossom drop are not exclusive to heirloom tomatoes, it's just a tomato "thing" since there's no difference in the blossom structure or pollen composition that would make heirlooms susceptible to blossom drop and not hybrids.

No shaking of plants or manual attempts at pollination are going to work if the pollen has been destroyed by high heat or sustained humidity has clumped the pollen. And I think I mentioned above that growing in too rich soil or container mix is also known to not just inhibit blossom formation, but also inhibit those blossoms from setting fruit b'c of the stress that using too much fertilizer or the too rich soil imparts to the plants also are variables.

Carolyn, who has lots of CA tomato friends and almost ALL of them are complaining about the lousy weather this season and lack of decent performance of their tomatoes. but for sure there are those who put their plants out way to late and are now paying the price.

I just can't get passed the little "patio" tomato plants in the wine barrel with the same potting mix, same watering, same fertilizer are loaded with tomatoes.

Here is my Heirloom.. (in the ground) the one in the wine barrel is identical.. about 6' tall with blooms, no fruit.

Here's a question, all of my plants did okay while the weather was cooler except one, Jersey Devil. It didn't do blossom drop, just didn't make blossoms at all. Looked like it was going to make a bunch of flowers, but when they opened there were no yellow petals in there at all.

ZZ, I don't know if I mentioned it above but growing in too rich soil or same for container mix and using too much fertilizer can inhibit not only blossom formation but fruit set as well. That plant you showed looks like one healthy plant to me but yet I wonder.

Surely there's a differenence in what's inground ( soil) and what's in the container mix in the wine barrel. Yes?

Muck 4, I know what you mean and have seen it before, it's due to the blossom formation being aborted.

No, I don't know the specific reason why that happens, it just does.

Both plants are identical. one in ground and one in a wine barrel.. both plants look awesome, plenty of blooms.. (on the ground LOL) I only use Fish emulsion fertilizer and I've stopped, in case that was the problem.

We have been under the 90s for several days. I HAVE A BABY. I'm gonna need a ladder to reach it by the time it ripens. but i have a baby Heirloom.

Organic Joe, have you used that product in high heat periods?

I see it is only "growth hormones" for increasing cell growth and am wondering if that would actually increase pollination or fruiting, whether from parthenocarpy or a more "natural" way. After all, it's the heat/humidity that zaps the pollen so unless the growth hormone (as opposed to IAA ) makes the flower "begat" fruit I wonder how it works.

Joe, you know I've been having problems getting stuff posted here at DG and I'd written a long post about Blossom Set spray but it wouldn't post so I'm trying again.

In a nutshell, no it won't work to help fruit set unless temps are cooler, not when temps are high.

it was devised to be used primarily in the PNW where springs are cool so pollenation is not good. But using it also induces parthenocarpy which is fruit set without pollination, so fruit development is abnormal.

The earliest fruits usually have no to few seeds and fruits can sometimes be mushy and malformed.

Shoe, at the molecular level I'm not sure how it induces parthenocarpy, but IAA ( indole acetic acid) is one of the most common of the cytokines added in most brand names of Blossom Set.

Dr. Jim Baggett of Oregon State has bred and released several parthenocarpic varieties and Oregon Spring, which is one that I've grown, is perhaps the best one known.

Carolyn, you may remember that in the spring I mentioned that I'm growing a new parthenocarpic sweet pepper variety, "Planet". Your comment was 'why in the world would someone need a parthenocarpic pepper' - since unlike tomatoes, peppers usually have no problem setting fruit.

We're harvesting ripe peppers now, and you were exactly right. Planet is a perfectly good pepper, but it's no more productive and has just as many seeds as my other sweet peppers. Maybe they all self-pollinated and the parthenocarpic thing never came into play, I don't know. For me, the expensive seeds aren't worth it since there's no difference in the end result.

Even in this difficult hot year, all my tomato plants finally set on fruit - I have hundreds of green ones set on now (81 days after transplanting), but they'll be late to ripen. I think if tomato plants are kept healthy, they'll find a way eventually.

Carolyn said, "Joe, you know I've been having problems getting stuff posted here at DG and I'd written a long post about Blossom Set spray but it wouldn't post so I'm trying again."

I think your post came through but there is another thread around here somewhere about this same topic so I bet that is where it is, Carolyn.

Thanks for the input. I remember reading the blossom set was only good for cooler climates, no good in heat. And yep, I even grew Oregon Spring some years ago. It was so-so but didn't really care for it much. :>) And thanks for the IAA info. I wasn't even aware it was considered a cytokine I guess that is an umbrella term for any growth hormone(?).

Congrats on your tomatoes coming on finally, Ozark! Hope your okra is following suit now!

A long while ago I grew Oregon Springs and they were prolific, The goodnes stoped right there. No taste I quit. There are to many good tasting tomatoes to grow Oregon Springs

Same here, Ernie. It was a tomato but others had more flavor.

By the way, are you getting the excessive heat over your way this year? Seems like it is covering the whole nation.

Nope Shoe I havent had any hot weather.

That does it. moving to WA!

Shoe (wondering do I need shoes over that way. )

so that must be what happened to my tomatoes. Never could get them to grow up in northern ohio while we lived there now down in FL we picked up a few and they were going good, then nothing and they look like they are dying. am I never going to get a nice home grown tomato. I had another gardener from the area say that when the nighttime temps stay high that that is what does in the plants. anyone else agree with this.

When we lived in KY we grew tomatoes all the time and we had lots of humidity. so what is the difference? Help!

meadowyck, yep, night time temps need to drop to at least 70-75 for good pollination. I know your town quite well (born there) and your best bet is to do a fall/winter grow-out for tomatoes summer is too hot.

thanks Shoe, all a gal wants is some home grown maters.

What month this fall do ya think I should start them? I'm going shopping for seeds so I can have lots of tomato varieties.

Shoe lots of room in Washington. The weather is cool though. It's gonna be a scortcher today though at least 68 or 70 . When I got up at 5.30 it was 49 now it is 58.

>>"Shoe lots of room in Washington. The weather is cool though. It's gonna be a scortcher today though at least 68 or 70 . When I got up at 5.30 it was 49 now it is 58."

Sheesh, Ernie! I bet ya'll are sweating to death! What a heat wave! :>)

Jan, here is a guide I found online. It's been a million years since I've been in Florida. It looks like September is when you set out your tomato plants in mid-Fla.

Off into the heat again. Hope your weather is much cooler!

thanks so much for the link shoe, I appreciate you taking the time to look for it and post.

look out matter, here I come September. LOL

I think what I saw on that link was plants go in during Sept. If you are starting from seed give yourself about six weeks to have them ready. Might want to start some seeds for tomatoes now.

We have several great Fla members here. I'll send them this way for more guidance.

Hope the Gulf is free of red tide, the fish are biting on Longboat Key, and the manatees are happy in the river!
Best to you and yours,

no red tide as yet, at least it hasn't bothered my asthma. we are on Palma Sola Bay.

Well, we had a spell that was spring like weather.. nights were so cool. My heirlooms are loaded with tiny fruit.. Looks like about Christmas we will get tomatoes!! LOL (just kidding) but they are sure late.

This is my harvest of the same variety.. (Belgium Giants) and Black Krim in the the picture. I only dream of a harvest like that again!!

Oh what I wouldn't give for some of them there maters. LOL what a beautiful picture of some might tasty eating.

Jan we have been munching on these for three weeks.

ok now you are rubbing the salt into the wound or should I say mater.

Jan mater moter teeter toddder in Florida it is really hotter.It is about 52 here right now but it is supposed to br in the 70 this week with Friday being a blistering 78. You can bet I will be hiding in the house that day.

Eweed what kind are those?

oh my 78 why that is perfect weather to be out in not inside the house. LOL

1Liasac those are red and ripe f5 moretons that I have been stablizing for five years now.

eweed - we've had so many 90F days, that the mid-80's feels "cool". We we set a record of 101F a couple of days ago. My indoor thermostat is set at 84F - I long for the temps to go down to 78!

I rec'd an email from Carolyn this morning saying she's tried seven times to post a response here. She's had this problem off and on, opening threads, posting to some, etc. She's asked me to copy/paste the following to you in answer to your question re "when to plant".

Her words begin here:
Jan, I have quite a few FL friends and for several years they'd send me a box of home grown tomatoes for Xmas. LOL My best long time friend is Linda Sapp who owns TOmato Growers Supply in Fort Myers whom I've known since the early 90's and many of the varieties she offers, of the OP heirloom kind, were from me. I still send her varieties to trial but since Vince, her late husband died, it's been tough for her alone to do the trials herself, especially after moving to a new home.

The key to being able to grow good ones is to sow your seeds between Xmas and early January and get those transplants out there by late Feb to early March.

That way they have time to grow and set and mature fruits before the high heat and humidity set in for the summer.

You could even try to do a Fall crop if you wanted to. It works well for some and not for others. Some will try to keep the plants going over the summer knowing they aren't going to produce, and then let them revive in the early Fall when the weather moderates. Some folks will even trim them back in late summer before the Fall revival, if you will.

That wouldn't work for me b'c I always have to be growing new varieties I haven't grown before so for a Fall crop the varieties wouldn't be the same as the Spring crop.

So there you have it in a nutshell, eh? And I hope Carolyn gets either her computer fixed for posting or DG can figure out what's wrong.

CBSE previous Year Solved Papers Class 12 Biology Outside Delhi 2012

Time allowed : 3 hours Maximum Marks: 70

General Instructions :

  1. There are a total of 26 questions and five sections in the question paper, All questions are compulsory.
  2. Section A contains question number 1 to 5, Very Short Answer type questions of one mark each.
  3. Section B contains question number 6 to 10, Short Answer type I questions of two marks each.
  4. Section C contains question number 11 to 22, Short Answer type II questions of three marks each.
  5. Section D contains question number 23, Value Based Question of four marks.
  6. Section E contains question number 24 to 26, Long Answer type questions of five marks each.
  7. There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examined is to attempt any one of the questions out of two given in the question paper with the same question number.


Question.1. Why is banana considered a good example of parthenocarpy ?
Answer: Banana is considered a good example of parthenocarpy because formation of fruit in banana occurs without fertilization (parthenocarpy), i.e., there is no formation of seeds.

Question.2. State two different roles of spleen in the human body.
Answer : The roles of spleen in the human body is that the spleen is the secondary lymphoid organ that produce lymphocytes and the red pulp of spleen removes the old or damaged red blood cells from the body.

Question.3. A garden pea plant produced axial white flowers. Another of the same species produced terminal violet flowers. Identify the dominant traits.
Answer : The dominant traits are : Axial, violet flower.

Question.4. Why is it desirable to use unleaded petrol in vehicles fitted with catalytic converters ?
Answer: It is desirable to use unleaded petrol in vehicles fitted with catalytic converters because lead in petrol inactivates the catalysts which convert harmful pollutants (CO, unburnt hydrocarbons, nitric oxide) to lesser harmful pollutants (C02,H2o,N2).

Question.5. Where is acrosome present in humans ? Write its function.
Answer: The anterior portion of the sperm head in human beings is covered by a cap-like structure called acrosome. Function of Acrosome :
(i) Acrosome is filled with hydrolytic enzyme-Hyaluronidase that aids in the entry of sperm into the ovum.

Question.6. Write the name of the following :
(a) The most common species of bees suitable for apiculture
(b) An improved breed of chicken
Answer : (a) Apis indica is the most common species of bees for apiculture.
(b) Leghorn is an improved breed of chicken.

Question.7. Comment on the similarity between the wing of a cockroach
and the wing of a bird. What do you infer from the above, with reference to evolution ?
Answer : The wing of a cockroach and the wing of a bird are not similar anatomically i.e., not similar in structure but similar in function. Thus we infer that these organs are analogous which has resulted in convergent evolution.

Question.8. Mention the role of cyanobacteria as a biofertiliser.
Answer: The role of cyanobacteria as a biofertiliser : Cyanobacteria (Anabaena and- Nostoc) are free-living in the root nodules of leguminous plants and they fix atmospheric nitrogen. They act as a bio-fertilizers especially in paddy fields.

Question.9. (a) Draw a neat labelled diagram of a nudeosome.
(b) Mention what enables histones to acquire a positive charge.
Answer: (a)

(b) Depend on the abundance of basic amino acid residues of lysines and arginines with charged side chain.

Question.10. State one advantage and one disadvantage of cleistogamy.
Answer: Advantage of cleistogamy: Self-pollination is assured, seed production is also assured in the absence of pollinators., Disadvantage of cleistogamy: In cleistogamous flowers due to self-pollination least variations observed.

Question.11. (a) Where do the signals for parturition originate from in humans ?
(b) Why is it important to feed the newborn babies on colostrum ?
Answer : (a) The signals for parturition in humans originate from the fully developed foetus and the placenta which include mild uterine contraction.
(b) The colostrum or first milk is important to feed the new born babies because it contains antibodies (IgA), to provide passive immunity to the baby.

Question.12. (a) A recombinant vector with a gene of interest inserted
within the gene of a-galactosidase enzyme, is introduced into a bacterium. Explain the method that would help in selection of recombinant colonies from non-recombinant ones.
(b) Why is this method of selection referred to as “insertional inactivation” ?
Answer: (a) Bacteria is grown in a medium with chromOgenic substrate, blue coloured colonies with no recombinations and colonies with no blue colour show presence of recombinants.
Chromogenic substrate used to identify recombinants and non-recombinants
(b) Gene for the enzyme is inactivated by insertion which is referred to as insertional inactivation.

Question.13. Explain brood parasitism with the help of an example.
Answer: Brood parasitism involves the use of host individuals of the same or different species to raise the young of the brood parasite. This relieves the parasitic parent from the investment of rassing young or building nests, producing offspring etc.
eg : The cowbird family is the bird family in North America is an brood parasite (because are not capable of building a nest). While most brood parasites have eggs that mimic the hosts eggs the cowbird is again different.

Question.14. Give reasons for the following :
(a) The human testes are located outside the abdominal cavity.
(b) Some organisms like honey-bees are called parthenogenetic animals.
Answer : (a) To maintain the temperature (2-2.5°C) lower than the normal internal body temperature,, which is essential for spermatogenesis.
(b) The phenomenon of development of female gamete directly into an individual without fertilization is called parthenogenesis. Example : The drones/males develop from unfertilised eggs of honey bees.

Question.15. Name the plant source of ganja. How does it affect the body of the abuser ?
Answer : Plant source : Cannabis Sativalhemp plant.
Affect: It damages cardio-vascular system of the body
Name the two special types of lymphocytes in humans. How do they differ in their roles in immune response ?
Answer: B lymphocytes, T lymphocytes.
B-cells produce pathogen specific antibodies called humoral immune response.
T-cells help the B-cells to produce antibodies and are responsible for direct cell mediated immunity.

Question.16. (a) Mention the cause and the body system affected by ADA deficiency in humans.
(b) Name the vector used for transferring ADA-DNA into the recipient cells in humans. Name the recipient cells.
Answer : (a) The body system affected by ADA deficiency in humans is immune system. ADA deficiency is caused due to lack the gene coding for adenosine deaminase.
(b) A retroviral vector is used to transfer ADA-DNA into recipient cells. The recipient cells are lymphocytes.

Question.17. How did Ahmed Khan, plastic sacks manufacturer from Bangalore, solve the ever – increasing problem of accumulating plastic waste ?
Answer : Ahmed Khan, a plastic sacks manufacturer solve the ever increasing problem and accumulation of waste. Polyblend fine powder of recycled modified plastic can be used to lay roads that will increased road life. When blended with bitumen, it enhances the bitumen’s water repellent properties and increase the life of road.

Question.18. Name the bacterium that causes typhoid. Mention two diagnostic symptoms. How is this disease transmitted to others ?
Answer : Bacterium: Salmonella typhi.
Diagnostic Symptom: Constipation, stomach pain, headache, weakness, loss of appetite, high fever.
The disease is transmitted through contaminated food and water.

Question.19. (a) Explain the phenomena of multiple allelism and codominance taking ABO blood group as an example.
(b) What is the phenotype of the following:
(i) (< I >^< A >)i (ii) ii
Answer: Multiple allelism : (a) In humans, the ABO blood groups are controlled by a gene called gene ‘I’. It has three alleles, (< I >^< A >), (< I >^< B >) and i, hence, referred to as multiple allelism. Co-dominance : If (< I >^< A >) and (< I >^< B >) both are present in an individual, and they both are expressed because of the phenomenon of co-dominance.
(b) (i) Phenotype of (< I >^< A >) / : A blood group.
(ii) Phenotype of i i: O blood group,

Question.20. How does industrial melanism support Darwins theory of Natural Selection ? Explain.
Answer: In England, before industrial revolution the environment was unpolluted. The white-winged moths were more and lichens on the barks of trees were pale. The white-winged moths could easily camouflage, while the darkwinged were spotted out by the birds for food. Hence, they could not survive. After industrial revolution the lichens became dark (due to soot deposit). This favoured the dark-winged moths while the white-winged were picked by birds. The population of the former which was naturally selected increased.

Question.21. (a) What is the programme called that is involved in
improving success rate of production of desired hybrid and herd size of catde ?
(b) Explain the method used for carrying this programme for cows.
Answer: (a) Multiple ovulation embryo transfer Technology/ MOET is used for improving success rate of production of desired’hybrid and herd size of cattle.
(b) Methods used for carrying this programme for cows :

  1. The cow is administered with FSH to induce follicular maturation and super – ovulation to produce 6 to 8 eggs.
  2. The animal is either mated with an elite bull or artificially inseminated.
  3. The fertilised eggs 8-32 cells stage are recovered non- surgically and transferred to surrogate mother where they develop into an improved variety.

Question.22. Explain the function of each of the following :
(a) Coleorhiza (b) Umbilical cord (c) Germ pores
Answer: The function of each of the following:
(a) Goleorhiza : Protects the radical of (monocot) embryo.
(b) Umbilical cord : Transports nutrients and respiratory gases and metabolic wastes to and from mother and foetus!
(c) Germ pores : Allow germination of pollen grain and formation of pollen tubes.

Question.23. How is the amplification of a gene sample of interest carried out using Polymerase Chain Reaction (PCR) ?
Answer: Polymerase chain reaction (PCR) is a method in which the desired gene is synthesised in vitro in following steps:

  1. Denaturation : The double-stranded DNA is denatured by applying high temperature of 95°C for 15 seconds. Each separated single stranded strand now acts as template for DNA synthesis.
  2. Annealing: Two sets of primers are added which anneal to the 3′ end of each separated strand. Primers act as initiators of replication.
  3. Extension : DNA polymefase extends the primers by adding nucleotides complementary to the template provided in the reaction. A thermostable DNA polymerase (Taq polymerase) is used in the reaction which can tolerate the high temperature of the reaction. All these steps are repeated many times to obtain several copies of desired DNA.

Question.24. Trace the life-cycle of malarial parasite in the human body when bitten by an infected female Anopheles.
Answer : Plasmodium requires two hosts to complete its life cycle.When female Anopheles mosquito bites a healthy person. Sporozoite of Plasmodium gets into human blood through the bite of female Anopheles mosquito. The parasite multiply in liver cells and finally burst in liver cells and released in blood, then they get into red blood cells, where they further multiply asexually and burst in RBCs also and released toxic substance haemozoin (associated with fever and chills). After a while they change into gametocytes, which are picked up by the mosquitoes and the entire cycle occurs again.

Question.25. List the salient features of double helix structure of DNA.
Answer: The salient features of Double Helix structure of DNA:

  1. It is made of two polynucleotido chains where backbone is sugar phosphats constituted and bases project inside.
  2. There is complementary base pairing between the two strands of DNA. The amount of adenine is equal to thymine and the amount of guanine is equal to cytosine.
  3. The two strands are coiled in right-handed fashion and are anti-parallel in orientation. One chain has a 5’—>3′ polarity while the other has 3’—>5′ polarity.
  4. The diameter of the strand is always constant due to pairing of purine and pyrimidine, i. e., adenine is complementary
    to thymine while guanine is complementary to cytosine.
  5. The distance between the base pairs in a helix is 0.34 nm and a complete turn contains approximately ten base pairs. The pitch of the helix is 3.4 nm and the two strands are right-handed coiled.

How are the structural genes activated in the lac operon in E. coli ?
Answer: The structural genes activated in the lac operonin E. coil in the following manner :
Lactose consists of the genes lac z, y and a. Lactose acts as the inducer that binds with repressor protein and frees the operator gene. RNA polymerase freely moves over the structural genes, transcribing lac mRNA, which in turn – produces the enzymes responsible for the digestion of lactose.

Question.26. Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with any three examples.
Answer : The three examples of the above statement are :

  1. Nile perch introduced into Lake Victoria in East Africa led to the extinction of Cichlid fish.
  2. Invasive plants like Parthenium /Lantana /Eichhomia caused environmental damage and posed a threat to indigenous species.
  3. Introduction of African catfish (Clarias gariepinus) to aquaculture is a threat to indigenous Indian catfishes.

Question.27. (a) Tobacco plants are damaged severely when infested with
Meloidegyne incognitia. Name and explain the strategy that is adopted to stop this infestation.
(b) Name the vector used for introducing the nematode specific gene in tobacco plant.
Answer: (a) The infestation jyas prevented by strategy which was based on RNA interference or RNAi or gene silencing. During this process nematode specific gene is introduced into host plant (using Agrobacterium) which produce dsRNA. This specific mRNA of the nematode silenced and parasite dies.
(b) Agrobacterium tumifaciens vector are used for introducing the nematode specific gene in tobacco plant.

Question.28. (a) Taking one example each of habitat loss and fragmentation, explain how are the two responsible for biodiversity loss.
(b) Explain two different ways of biodiversity conservation.
Answer : (a) Habitat loss and fragmentation are responsible for biodiversity loss are :

  1. Habitat loss : The Amazon rainforest (called the “lungs of the planet”) is being cut and cleared for cultivation of soya beans and for conversion into grasslands for raising beef catde.
  2. Fragmentation : When large-sized habitats are broken or fragmented due to human setdements, building of roads, digging of canals, etc., the population of animals requiring large territories and some animals with migratory habitats declines.

(b) The two different ways of biodiversity conservation are :

  1. Ex situ
  2. In situ conservation.

Ex situ conservation : In this conservation threatened organism are taken out from the natural habitat and placed in special setting with care and protected, eg., zoological park, botanical garden, wild safari.
In situ conservation: In this conservation threatened organisms are conserved in their natural habitat, e.g, national , parks, biosphere reserves.
(a) What depletes ozone in the stratosphere? How does this affect human life?
(b) Explain biomagnification of DDT in an aquatic food chain. How does it affect the bird population?
Answer: (a) Chlorofluorocarbons (CFCs) released from the refrigerators air conditioners deplete ozene in the stratosphere. Ozone acts as a shield and protects the earth from, the harmful UV rays of the sun.
Effect on Human life : Chlorofluorocarbons depletes ozone layer causing UV rays to reach to earth which damages DNA causing mutation, skin cancer, inflammation of cornea, cataract, aging of skin, snow blindness.
(b) If DDT leaches from the agricultural field, it gets into the water body (the concentration is 0.0003 ppm) and enters the food chain:
zooplanktons (0.04 ppm) —> small fish (0.05 ppm) —» large fish (2 ppm) —» any fish eating bird (5 ppm). Concentration of DDT increases along the food chain, reaching a high level in the top carnivore bird.
Effect on Bird population : DDT concentration disturbs Ca++ metabolism, egg shells become thin, premature breaking resulting in decline in bird population.

Question.29. The following is the illustration of the sequence of ovarian events “a” to “i” in a human female:

(a) Identify the figure that illustrates corpus luteum and name the pituitary hormone that influences its formation.
(b) Specify the endocrine function of corpus luteum. How
does it influence the uterus ? Why is it essential ?
(c) What is the difference between “d” and “e” ?
(d) Draw a neat labelled sketch of Graafian follicle.
Answer: (a) Corpus luteum is illustrated by ‘g’ and the hormone influencing its formation is luteininsing hormone (LH).
(b) Corpus luteum produces the hormone progesterone, causes proliferation of the endometrium which gets highly vascularised. It is essential for the implantation of the fertilized ovum and maintains the same during pregnancy.
(c) “d” is the developing tertiary follicle, “e” is the Graafian follicle.

(a) Why is fertilisation in an angiosperm referred to as double fertilisation ? Mention the ploidy of the cells involved.
(b) Draw a neat labelled sketch ofL.S. of an endospermous monocot seed.
Answer: (a) Fertilisation of haploid egg cell by one haploid male gamete to form diploid zygote is called syngamy. Fertilisation of two (diploid) polar nuclei by the other haploid male gamete to form triploid primary endosperm nucleus is called triple fusion.
(b) L.S. of an endospermic monocot seed.

Question.30. Describe Frederick Griffiths experiment on Streptococcus pneumoniae. Discuss the conclusion he arrived at.
Answer : Frederick Griffiths experiment Transforming Principle conducted by him in 1928.

  1. Frederick Griffith (1928) conducted experiments with Streptococcuspneumonia (bacterium causing pneumonia).
  2. He observed two strains of this bacterium—one forming smooth shiny colonies (S-type) with capsule, while other forming rough colonies (R-type) without capsule.
  3. When live S-type cells were injected into mice, they died due to pneumonia.
  4. When live R-type cells were injected into mice, they survived and he arrived at this conclusion
  5. When heat-killed S-type cells were injected into mice, they survived and there were no symptoms of pnuemonia.
  6. When, heat-killed S-type cells were mixed with live R-type cells and injected into mice, they died due to unexpected symptoms of pneumonia.
  7. He concluded that heat-killed S-type bacteria caused a transformation of the R-type bacteria into S-type bacteria but he was not able to understand the cause of this bacterial transformation.

(a) Explain a monohybrid cross taking seed coat colour as a trait in Pisum sativum. Work out the cross up to F2 generation.
(b) State the laws of inheritance that can be derived from such a cross.
(c) How is the phenotypic ratio of F2 generation different in a dihybrid cross ?
Answer : (a) A monohybrid cross taking seed coat colour as a trait in Pisum sativum, for e.g if pea plant with yellow seed coat is crossed with pea plant having green seed coat then in the Fj generation all the plants are yellow seeds.

F2 Phenotypic ratio = 3:1
F2 Genotypic ratio =1:2:1
The law of inheritance can be derived from such a cross :
(b) (i) Law of Dominance: Factor occurs in pairs. In a contrasting pair of factors one member of the pair dominates (dominant) the other (recessive).
(ii) Law of Segregation : Factors or allele of pair segregate from each other such that gamete receives only one of the two factors. Paired condition is restored at the time of zygote’ formation.
(c) Phenotypic ratio of F2 generation in monohybrid cross is 3 :1 whereas in a dihybrid cross the phenotypic ratio is 9 : 3 : 3 : 1.


Question.1. How do the pollen grains of Vallisneria protect themselves ?
Answer : The pollen grains of Vallisneria have mucilaginous covering to prevent them from getting wet.

Question.2. Name the respective pattern of inheritance where Ft phenotype.
(a) does not resemble either of the two parents and is in between the two.
(b) resembles only one of the two parents.
Answer : (a) The respective pattern of inheritance where phenotype not resemble either of the two parents and is in
between the two known as Incomplete dominance.
(b) resembles only one of the two parents Law of Dominance.

Question.5. How is the entry of only one sperm and not many ensured into an ovum during fertilisation in humans ?
Answer : During fertilisation in humans: At the sperm head there is an enzyme to dissolve the follicles of ovum and facilitate entry of the sperm nucleus for fertilization and help the sperm enter into the cytoplasm of the ovum.

Question.7. State the significance of Coelacanth in evolution.
Answer : It is an ancestor of amphibians. The latest analysis shows that the genes of modern coelacanths’can-themselves be considered living fossils.

Question.12. Name the source organism that possesses Taq polymerase.
What is so special about the function of this enzyme ?
Answer: Thermus aquaticus.
The enzyme can tolerate high temperature and is thermostable. It does not get denatured during PCR at high temperature.

Question.13. State one advantage and one disadvantage of cleistogamy.
Answer : Advantage : Cleistogamy flowers produce assured seed set even in the absence of pollinators to increase genetic variations. Disadvantage: The disadvantage of Cleistogamy is the offspring produced have limited genetic diversity.

Question.15. Name the source of cyclosporin-A. How does this bioactive molecule function in our body ?
Answer: The source of cyclosporin-A Trichoderma polysporum.
Bioactive molecule function in our body: It is used as an immuno-suppressant agent in organ transplant patient.
(a) Name the group of viruses responsible for causing AIDS in humans. Why are these viruses so named ?
(b) List any two ways of transmission of HIY infection in humans, other than sexual contact.
Answer : (a) The group of viruses responsible for causing AIDS in humans iis Retrovirus. These are named so because they (have RNA genome) have reverse transcriptase enzyme which carries on die processes RNA —> DNA —» RNA.
(b) (i) Transfusion , of infected blood.
(ii) Sharing infect ed syringes and needles. .
(iii) Children bor n to HIV mother through placents.

Question.17. Name any two or ganisms that are responsible for ringworms in humans. Mention two diagnostic symptoms. Name the specific parts of the human body where these organisms thrive and explain why.
Answer : Micro sporum and Trichophyton are two organisms that are responsible for ringworms in humans.
Symptoms : Dry and scaly lesion on skin, nails, scalp, intense itching These thrive in body groin, between toes, thrive better in heat, moisture, perspiration.

Question.19. Differentiate between perisperm and endosperm giving one example of each.

Question.25. (a) List any three ways of measuring population density of a habitat.
(b) Mention the essential information that can. be obtained by studying the population density of an organism.
Answer : There are different ways of measuring population density of a habitat are as follows :

  1. Quadrat method: This method involves the use of square of particular dimensions to measure, no. of organisms.
  2. Direct observation : This method is used for counting of organism.
  3. Indirect method : This method is used for the number fish caught per trap gives the measure of their total t density in a given water bod y.

(b) The population density of an organism provides us the status of habitat, whether competition for survival exists or not, whether population is increas ing or declining, natality, mortality, emigration, immigration.

Question.28. (a) Explain the significance of ecological pyramids with the help of an example.
(b) Why are the pyramids referred to as1 upright’ or ‘inverted’ ?
Answer : (a) Ecological pyramid expresses the relationship between the organisms at differen t trophic levels with reference to their number, energy and biomass.

Upright Pyramid : In this pyramid producers are more in number and in biomass than the herbivores, and herbivores are more in number and biomass than the carnivores. The Pyramid of energy is always upright as only 10% energy is transferred from one trophic level to the next.
Inverted pyramid: It shows less number/biomass of producers when compared to primary consumers. For e.g. large number of insects feeding on a big tree give inverted pyramid of number.
(a) Explain giving reasons why the tourists visiting Rohtang Pass or Mansarovar are advised to resume normal ‘active life’ only after a few days of reaching there.
(b) It is impossible to find small animals in the polar regions. Give reasons.
Answer: (a) The tourists visiting Rohtang Pass or Mansarovar are advised to resume normal active life’ only after a few days of reaching there because initially the person suffers from altitude sickness, nausea, fatigue and heart palpitation because of low oxygen availability and low atmospheric pressure. Gradually the body increases RBC production, decreasing binding capacity of Hb and increases the breathing rate to get acclimatised. •
(b) Small animals are rarely found in polar regions because small birds have larger surface area relative to their volume, so they lose heat much faster spend more energy to generate body heat. They have to expand much energy to generate body heat through metabolism.


Question.1.Identify the figure given below and the part Labelled “A”.

Answer:The figure is of blastula/blastocyst.

Question.2. How do interferons protect us ?
Answer : Interferons protect uninfected cells from further viral infections, by creating cytokine barriers.

Question.3. Name the interaction between a whale and the bar nacles growing on its back?
Answer : Commensal ism is the interaction between a wdiale and the barnacles grow ing on its back.

Question.7.In a dihybrid cross, when would the proportion of parental . gene combinations be much higher than non-parental types, as experimentally shown by Morgan and his group ?
Answer: When the genes are present on a same chromosome or incomplete linkage is present then the proportion of parental gene combinations be much higher than non-parental types,* according to Morgan and his group.

Question.12. Name the cells that act as HIV factory in humans when infected by HIV. Explain the events that occur in the infected cell.
Answer : Macrophages/Helper T-cells act as HIV factory in humans.
The events occur in the infected cell:

  1. HIV attached to CD-4 cell with GP-120 to CD-4 protein.
  2. Reverse transcription by reverse transcriptase, enzyme.
  3. Its DNA attached with host cell DNA.
  4. Multiplication of HIV.
  5. Lysis of infected cell.

Question.15. Name and explain the two types of immune responses in humans.
Answer: The two types of immunity are active immunity and passive immunity.
Active immunity: Immunity developed in the host body due to production of antibodies in response to antigens which of low intensity and produce memory cells.
Passive immunity : When ready-made antibodies are direcdy given to protect the body against foreign agents which is of very high intensity.

Question.16. How does the study of different parts of a flower help in identifying in wind as its pollinating agent ?
Answer: Pollination in which wind distributed the pollens is called anemophily.
Wind pollinated flowers have light and non sticky pollen grains, well exposed stamens to disperse pollen easily, large and often feathery stigma for easy trapping of pollen, single ovule in each ovary, numerous flowers packed into an inflorescence.

Question.22. Explain how do the following act as contraceptives :
(a) CuT (b) “Saheli”
Answer: (a) CuT release Cu ions when inserted into the uterus which suppress sperm motility, lowers the fertilising capacity of sperms. These devices inserted by doctors as experts in the uterus through vagina
(b) Oral contraceptive for the female! contain a non-steroidal preperation. It is once a week pill with very few side effects and high contraceptive value inhibit ovulation, implantation, as well as alter the quality of cervical mucus to prevent or retard the entry of sperms.

Question.26. Name and explain the evolutionary concept represented in the illustration given below:

Answer : The illustration represents adaptive radiation or divergent evolution.
It is the example of adaptive radiation in placental animals of Australia.

  1. A variety of placental mammals have evolved which appear similar to a corresponding marsupial.
  2. When more than one adaptive radiation appeal to have occurred in an isolated geographical area, and two or more
    groups of unrelated animals come to resemble each other for similar mode of life or habitat, it is called convergent evolution.

(a) Why is it that the father never passes on the gene for haemophilia to his sons? Explain.
(b) State the functions of the following in a prokaryote :
(i) tRNA (ii)rRNA
Answer: (a) The father never passes on the gene for haemophilia to his sons because haemophilia is a sex-linked recessive disease and the defective.Gene is present on X chromosome only and not on Y chromosome.
(b) Function of t-RNA in prokaryotes –
(i) tRNA reads the genetic codes, carries amino acids to the site of protein synthesis and act as an adap tor molecule.
(ii) rRNA plays structural and catalytic role during translation .

Question.30. (a) A garden pea plant bearing terminal, violet flowers, when crossed with another pea plant bearing aixial, violet flowers, produced axial, violet flower and axtial, white flowers in the ratio of 3 : 1. Work out the cross showing the genotypes of the parent pea plants and their progeny, (b) Name and state the law that can be derived from this cross and not from a monohybrid cross.
Answer: (a)

(b) This cross is based on Law of Independent Assortment. This law states that when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of character.
(a) Describe the process of synthesis of fully functional mRNA in a eukaryotic cell.
(b) How is this process of mRNA synthesis different from that in prokaryotes?
Answer : (a) The process of synthesis of fully functional mRNA in a eukaryoic cell.

  1. The primery transcrips are non-functional, containing both the coding region, exon, and non-coding reigion, irron, in RNA and are called heterogenous RNA or hnRNA.
  2. The hnRNA undergoes two additional process called cappint and tailing.
  3. In cappint, an unusual nucleotide, methyl guanosine triphosphate, is added to the 5′-end of hnRNA.
  4. In tailing, adenylate rersidues (about 200-300) are added at 3–end in a template independent manner.
  5. Now the hnRNA undergoes a process where the introns are removed and exons are joined to form mRNA by the process called splicing.

(b)In prokaryotes, there is a single DNA-dependent RNA polymerase that catalyses transcription of all types of RNA in bacteria. In bac teria, mRNA does not require any processing as it does not have any introns.


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Keywords : Banana/plantain, evolution, structural genome, disease resistance, parthenocarpy, dwarfism, biotic and abiotic stress, comparative genomics

Citation: Dash PK and Rai R (2016) Translating the “Banana Genome” to Delineate Stress Resistance, Dwarfing, Parthenocarpy and Mechanisms of Fruit Ripening. Front. Plant Sci. 7:1543. doi: 10.3389/fpls.2016.01543

Received: 06 August 2016 Accepted: 30 September 2016
Published: 26 October 2016.

Swarup Kumar Parida, National Institute of Plant Genome Research, India

Ying Wang, South China Institute of Botany (CAS), China
Rajesh MK, ICAR-Central Plantation Crops Research Institute, India

Copyright © 2016 Dash and Rai. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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