Question

Question 14 4 pts Suppose that rats have a diploid chromosome number of 42 (2n=42]). How many chromatids will be present in a cell that is in the middle of mitosis metaphase? Hint: Mitosis Phases video Textbook chapter 10 section 10.2 Chapter 10 Practice Question 1 (see chapter 10 ase) 21 BB 168 9 O ct

Answer 1

1) during S phase the DNA replicates and the 2 daughter double-stranded DNA molecules are attached to each other at the centromere, 2 daughter DNA molecules attached to each other at the centromere is are sister chromatids.

42 chromosomes divide during S phase then the total number of sister chromatids=2 $\times$ 42=84

so the answer is 84.

2) during mitosis, firs the nuclear envelope disintegrates, the chromatin condenses to form chromosomes, then mitotic spindle attach to the chromosomes at the kinetochore and these chromosomes align at the metaphase plate, then during anaphase, the cohesin protein which holds 2 sister chromatids together disintegrates and the sister chromatids are separated and moves to opposite poles, then chromatids reach at the poles and nuclear envelope reforms at the poles.

so the answer is b) the mitotic spindle becomes attached to the kinetochore, sister chromatids line up at the metaphase plate, cohesin proteins degrade and sister chromatids separate. The nucleus reforms and the cell divides.