Question

You are studying a plant that requires a period of cold treatment before it will flower. You subject a plant to cold treatment, return it to temperatures favorable for growth, and then compare the chromatin state of the DNA taken from:

(1) meristem cells from a shoot that originated before the cold treatment;

(2) meristem cells from a shoot that developed after the cold treatment;

(3) ovule egg cells from a flower on stem 1;

(4) seeds from a flower on stem 2.

You find that the chromatin states are the same within but differ between which two groups?

		2, 4 versus 1, 3
		1 versus 2, 3, 4
		1, 3 versus 2, 4
		1, 2 versus 3, 4

Answer 1

Answer- 1,2 versus 3,4

Explanation- the plant requires period o cold treatment before flowering and when plant will subjected tocold treatment, plant shows flowering. The chromatin states are compared in different plant parts and they are found different.

(1).and (2) group shows same chromatin content versus (3) and (4) =

1. Meristem cells from a shoot that originated before the cold treatment =meristem cells are somatic cells so that these cells contains pairs of chromosomes before cold treatment.

2. Meristem cells from a shoot that originated after the cold treatment =meristem cells are somatic cells and they will always diploid (pair of chromosomes). So that after cold treatment meristem cells from a shoot contain pairs of chromosomes.

3. Ovule egg cells from a flower on stem 1= ovule is female gamete that contains egg cell which is haploid. This egg cell contains one set of chromosomes.

4. Seeds from a flower on stem 2= seed is formed after fertilization of pollen grain with egg cell and polar nuclei. When sperm fuses with egg cell, the diploid zygote is formed that will develop into embryo which has pairs of chromosomes. Second fusion is fusion of sperm with diploid polar nuclei forms triploid endosperm. So that seed contains diploid embryo and triploid endosperm.