Question

Find out the number of bivalents in zygotene stage, if there are 60 chromosomes in $G_1$ phase.

• A. 60
• B. 30
• C. 15
• D. 45

Answer 1

The correct option is B 30

• When the zygotene stage begins, the homologous chromosomes pair up to for bivalents or tetrads.
• If there are 60 chromosomes in G1 phase, then after S phase, there would be 120 chromosomes.
• And we know that each bivalent is formed of 4 chromosomes so there will be 120%4=30bivalents in zygotene stage.
• Hence, 30 number of bivalents in zygotene stage, if there are 60 chromosomes in G1 phase.
• So, the correct answer is '30'.