In flowering plants, DNA content of the parent plant gets halved during
- A.Seed germination
- B.Fruit formation
- C.Flower bud formation
- D.Pollen formation
Correct answer
Explanation
The correct answer is D, Pollen formation. Pollen grains are formed by meiosis, the division that halves the chromosome number and DNA content of the parent cell.
Inside the anther, each pollen mother cell (microspore mother cell) is diploid. It divides by meiosis to form a tetrad of four haploid microspores, which develop into pollen grains. In the same way, the megaspore mother cell in the ovule divides by meiosis to give the haploid megaspore. Halving the DNA before fertilisation matters: when a male gamete fuses with the egg, the zygote gets back the full diploid set, so the chromosome number stays constant from one generation to the next.
A is wrong because a germinating seed grows by mitosis, which keeps the DNA content the same.
B is wrong because the fruit develops from the ovary wall through mitotic growth.
C is wrong because a flower bud forms from the shoot tip by mitosis, with no halving of DNA.
Exam tip: meiosis in flowering plants occurs in the anther (pollen formation) and in the ovule (megaspore formation).
Practice Questions
View allWhich one of the following is not true for anodizing process?
- A.It makes aluminium corrosion resistant.
- B.Metals like aluminium, titanium and magnesium can be anodized.
- C.Clean aluminium article is the anode and oxygen gas is evolved at the cathode.
- D.It is used in aircraft industry.
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In anodizing the clean aluminium article is indeed the anode, but oxygen is released at the anode, not at the cathode; hydrogen is released at the cathode.
Read the full explanation →Which one of the following statements is not correct?
- A.The response of the ear to sound of increasing intensity is approximately logarithmic.
- B.The sensitivity of the human ear does not vary with the frequency of the sound.
- C.When two or more waves traverse the same medium, the displacement of any element of the medium is the algebraic sum of the displacements due to each wave.
- D.Longitudinal waves can travel in all media—solids, liquids and gases.
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The statement that the sensitivity of the human ear does not vary with frequency is false, because the ear is far more sensitive to some frequencies than to others.
Read the full explanation →Kwashiorkor disease in children is caused by
- A.sufficient carbohydrates but less fats in diet
- B.sufficient carbohydrates and fats but deficient proteins in diet
- C.sufficient vitamins but deficient fats in diet
- D.sufficient fats but deficient vitamins in diet
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Kwashiorkor is a disease of protein deficiency in a child who still gets enough calories. It usually appears when a child is weaned from breast milk onto a starchy diet with little protein.
Read the full explanation →Which one of the following is the correct order of pH for the given substances?
- A.Coffee < Lemon juice < Milk of magnesia < Blood
- B.Milk of magnesia < Blood < Coffee < Lemon juice
- C.Lemon juice < Blood < Coffee < Milk of magnesia
- D.Lemon juice < Coffee < Blood < Milk of magnesia
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Arranged from most acidic to most basic, the four substances fall in exactly this order. Lemon juice, rich in citric acid, has a pH of about 2 to 2.5.
Read the full explanation →Which one of the following diseases may be caused by the deficiency of vitamin C?
- A.Rickets
- B.Rabies
- C.Hepatitis
- D.Scurvy
Show answer
Scurvy is caused by a lack of vitamin C, or ascorbic acid, which the body needs to make collagen, the protein that holds skin, gums and blood vessels together.
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