We St. Kilda wrens have 43 pairs of chromosomes, for a total of 86. We don’t know much about bird chromosomes – only around 10% of species have been studied in this way, so far. We do know that, of the ones that have been studied, most have 78-80 chromosomes. So why are we wrens different; why d we ave more chromosomes? We don’t know. But if researchers are able to study our genome, we could find out.
Emperor Dragonflies have 13 pairs of chromosomes that are common to males and females, and like people their biological sex is determined by sex specific chromosomes.
Unlike people, male Emperor Dragonflies have a single X (sex) chromosome (27 chromosomes in total), whereas females have two X chromosomes, for a total of 28 chromosomes – so they have a proper “spare” set. Amazingly this was only determined for Emperor Dragonflies in 2002, by the Russian Scientists Perepelov and Bugrov – showing how much there is to learn about us!
The chromosome count, or karyotype, of the lesser-spotted catshark is 40 pairs of chromosomes, or 80 in a typical diploid cell. As you might know diploid organisms have 2 pairs of chromosomes (1 from each parent). In genetics we call the diploid state 2n and the haploid state representing the number of chromosomes in sperm or egg cells 1n. So in the catshark we would say 2n=80 or 1n=40. This is quite a lot more chromosomes than humans have (1n=23, 2n=46)! But did you know that some cells can have greater or fewer chromosomes than the typical value. This is true of human liver cells where genome doublings can mean cells have up to 16 times more chromosomes than the typical value (up to 736 chromosomes)!