PREVIOUSLY ASKED IN:
PSC Miscellaneous Prelims 2018
Answer
46
Explanation
A normal human somatic (body) cell contains 46 chromosomes, arranged in 23 pairs. Out of these 23 pairs, 22 pairs (44 chromosomes) are called autosomes, which carry genes for physical characteristics. The remaining 1 pair (2 chromosomes) are the sex chromosomes, which determine the biological sex of the individual. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
Key Points
- > Human somatic cells have 46 chromosomes (23 pairs).
- > Human gametes (sperm and egg cells) are haploid, meaning they have only 23 chromosomes.
- > There are 22 pairs of autosomes (44 chromosomes).
- > There is 1 pair of sex chromosomes (XX in females, XY in males).
- > Down syndrome is caused by the presence of an extra 21st chromosome (Trisomy 21), making the total count 47.
- > Chimpanzees and potatoes have 48 chromosomes.
Additional Information
Chromosome Numbers in Various Species
| Species | Diploid Chromosome Number (2n) |
|---|---|
| Human | 46 |
| Chimpanzee | 48 |
| Dog | 78 |
| Cat | 38 |
| Onion | 16 |
| Pea Plant | 14 |
Memory Tips
- The 46 Formula: Remember the split 44 + 2. 44 are the builders (Autosomes) and 2 are the deciders (Sex chromosomes). Together they make 46.