Question

16. Knowing that the somatic cells of the mouse have 40 chromosomes. How many chromosomes will there be in:

a) A haploid cell:

b) A diploid cell:

c) A neuron in phase G2:

d) An oocyte:

e) A fibroblast in phase G1:

f) A tetraploid macrophage in G2:

Answer 1

a somatic cell is diploid

the diploid number of chromosomes= 40

the haploid number of chromosomes= diploid number of chromosomes/2=40/2=20

(the diploid cell has 2 sets of homologous chromosomes and haploid cell has only one set of chromosomes)

a) 20

b) 40

c) during G2 phase of the neuron the DNA has replicated but the number of chromosomes is the same as that of a somatic cell

( neuron is a somatic cell and cell cycle progress as G1, S, G2 phase, and DNA is replicated during S phase)

so the number of chromosomes in the G2 phase of the neuron is 40

d) oocyte is he female gamete, gametes are formed by the meiosis of the diploid cell, meiosis is reduction division, the number of chromosomes in the daughter cells is reduced by half in meiosis, the oocyte is haploid, the number of chromosomes in the oocyte is 20.

e) fibroblast is a somatic cell, number of chromosomes in the fibroblast=diploid number of chromosomes=40

f) tetraploid macrophage

number of chromosome in haploid cell= 20

n= 20

tetraploid is 4n

so number of chromosomes in the tetraploid macrophage is 204=80