Differentiate between the following pairs on the basis of what is mentioned within brackets:
Human skin cell and Human ovum (number of chromosomes)
Topic: Chromosomes in a body cell and a gamete
Answer
A HUMAN SKIN CELL contains 46 chromosomes — it is a body cell and therefore DIPLOID.
A HUMAN OVUM contains 23 chromosomes — it is a gamete and therefore HAPLOID.
The brackets restrict the answer to the NUMBER, so give the two figures plainly — 46 and 23.
WRITE 23, NOT 23 PAIRS, for the ovum. That single word is the commonest error in this question: a gamete carries 23 SINGLE chromosomes.
THE REASON gametes are halved: at fertilisation sperm and ovum fuse. If each carried 46 the zygote would have 92, doubling every generation. MEIOSIS halves the number so that fusion restores exactly 46 — which is why 23 + 23 = 46.
A skin cell is formed by MITOSIS (number unchanged), an ovum by MEIOSIS (number halved).
| Point of difference | Human skin cell | Human ovum |
|---|---|---|
| Number of chromosomes | 46 (23 pairs) | 23 |
| Condition | Diploid (2n) | Haploid (n) |
| Formed by | Mitosis | Meiosis |