A somatic cell that has just completed the S phase of its cell cycle, as compared to gamete of the same species, has
- twice the number of chromosomes and four times the amount of DNA
- four times the number of chromosomes and twice the amount of DNA
- twice the number of chromosomes and twice the amount of DNA
- same number of chromosomes but twice the amount of DNA.
Answer
(1) twice the number of chromosomes and four times the amount of DNA
Solution
Let the gamete (haploid) have chromosome number n and DNA content 1C.
⇒ A somatic cell in G1 has 2n chromosomes and 2C DNA.
As per NCERT, during the S phase the amount of DNA per cell doubles (2C → 4C), but the number of chromosomes remains the same (2n).
∴ Compared with the gamete: chromosomes = 2nn = 2 times, DNA = 4C1C = 4 times.
Answer: (1)