How many chromosomes does a rat have if the diploid set is forty‑two? - briefly
A rat’s diploid chromosome number is 42. Consequently, each somatic cell contains forty‑two chromosomes.
How many chromosomes does a rat have if the diploid set is forty‑two? - in detail
The laboratory rat (Rattus norvegicus) possesses a diploid chromosome complement of forty‑two chromosomes. This number represents the total count of chromosomes in somatic cells, where each chromosome exists in a homologous pair. Consequently, the haploid set, found in gametes, contains twenty‑one chromosomes.
Key points about the rat karyotype:
- Total somatic chromosomes: 2 × 21 = 42
- Autosomes: 20 pairs (40 chromosomes)
- Sex chromosomes: one pair (XX in females, XY in males)
The rat genome has been fully sequenced, confirming the 42‑chromosome arrangement across diverse strains. Cytogenetic analyses reveal that chromosome sizes range from large metacentric chromosomes to smaller acrocentric ones, facilitating identification during metaphase spreads. Comparative studies show that this diploid number is conserved among most laboratory rat lines, providing a stable reference for genetic research.