Question

Please explain the answers! Thanks.

(1) If a diploid cell in G2 has 66 DNA double helices, it must have ___ pairs of homologous chromosomes

(2) A cell in G2 has 24 DNA double helices. If this cell goes through meiosis, each gamete will have __ chromosomes

(3) A cell in metaphase I of meiosis 1 has 2 tetrads. When the cell was in G1, it had ___ pairs of chromosomes

Answer 1

Ans 1: 33

If the initial amount of DNA is denoted as 2C then it increases to 4C, because after S phase , due to replication takes place in S phase , so in G2 it is 4C.

Ans 2. 24 chromosomes

There is no increase in the chromosome number, even after S phase the number of chromosomes remains same in G2.

Ans 3 : 2 pairs

2 tetrads means 8 homologous chromatids

= 4 homologous chromosomes

= 2 pairs

During metaphase 1, chromosomes number remains same, because during S phase only the amount of DNA doubles but the number of chromosomes remains the same.

Now in meiosis 11, in metaphase 11 , it reduces to half

If there is 2 tetrads in metaphase1 there is 4 chromosomes( 2 pairs) and in metaphase 11 it reduces and becomes two chromosomes ( 1 pair).