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Rattus 2n = 42
2n = 42
Measured
Norway / laboratory rat standard karyotype 2n = 42.
The laboratory rat keeps its genome in forty-two chromosomes. Twenty autosome pairs and XY. A named committee wrote that down in 1973. The black rat next door is commonly 2n = 38. Same family, different count.
What it supports
Committee for a Standardized Karyotype of Rattus norvegicus, Cytogenetics and Cell Genetics 12 (1973) 199–205. 2n = 42 is the diploid number. Morphology of pairs can vary. The count does not. Bread wheat 2n = 42 is a different organism.
What it does not
Not every rat. R. rattus is often 38. Not wheat. Not a joke about lab animals.
ExactnessCount
Form42
Unitchromosomes
Strengthhard