Question

"Gametes must be produced by meiosis for sexual reproduction". Why is it so? [3 MARKS]

Answer 1

Explanation: 3 Marks

All organisms contain an even number (2n) chromosomes in their somatic cells. The chromosome number is fixed for a given species. For example, humans have 46 chromosomes. Any variation in the number of chromosome of the species would result in drastically different characters. Sexual reproduction means the fusion of a male gamete (called sperm in animal cells) with a female gamete (egg) resulting in the formation of a zygote from which the offspring develops. Suppose the sperm and the egg cell had diploid chromosomes (2n), Then, after fertilization (fusion), the offspring would have twice the number of chromosomes, deriving 2n from each parent cell (2n + 2n = 4n). Therefore in sexually reproducing organisms, the gametes are haploid (n), i.e. they contain half the number of chromosomes present in somatic cells to compensate for the doubling (n + n = 2n) in the zygote as a result of fertilization. This is accomplished by meiosis only. Thus, for sexual reproduction, gametes must be produced by meiosis.