Cell Division - Meiosis

A skin cell is a somatic (body) cell, which is diploid ($2n$). An egg cell is a gamete, which is haploid ($n$).

Meiosis reduces the chromosome number by half. If the diploid number is $2n=46$, then the haploid number is $n=46÷2=23$.

An egg cell contains 23 chromosomes. This ensures that when a sperm (also with 23) fuses with the egg during fertilisation, the resulting zygote has $23+23=46$ chromosomes.

The question asks for the chromosome number in a gamete (egg cell), given that body cells have 46 chromosomes.

46 is incorrect — that is the diploid number found in body cells. Gametes must have half this number so that fertilisation restores the diploid count.

92 is incorrect — this would be the number of chromatids after DNA replication, not the chromosome number in a gamete.

12 is incorrect — this has no biological basis for human cells.

23 is correct. Meiosis halves the chromosome number: $46÷2=23$, giving haploid gametes ($n=23$).

The term 'reduction division' refers specifically to the reduction in chromosome number that occurs during meiosis I, when homologous chromosomes are separated.

A diploid cell ($2n$) undergoes meiosis I to produce two haploid cells ($n$). The chromosome number is halved — in humans from 46 to 23. This reduction is the defining feature of meiosis I.

The correct answer is 'It reduces the chromosome number by half.' This is the fundamental reason meiosis is essential — it produces haploid gametes so that fertilisation restores the diploid number.

The question asks why meiosis is called 'reduction division' — what exactly is being reduced?

Cell size does decrease during meiosis, but this is not the reason for the specific name 'reduction division.' Cell size reduction is not a defining or unique feature of meiosis.

Each gene still has alleles after meiosis — the number of alleles per gene is not reduced. This option confuses allele variation with chromosome number.

DNA replication still occurs once before meiosis begins, just as in mitosis. Meiosis does not reduce the DNA replication step.

'It reduces the chromosome number by half' is correct. Meiosis I specifically separates homologous chromosomes, halving the chromosome count from $2n$ to $n$.