What are B chromosomes?
Q: What are B chromosomes?
A: B chromosomes are chromosomes that are not necessary for the life of a species, also called 'supernumerary' or 'accessory chromosomes'.
Q: Do all species have B chromosomes?
A: No, not all species have B chromosomes.
Q: Are B chromosomes essential for the life of a species?
A: No, B chromosomes are not essential for the life of a species.
Q: Are B chromosomes heterochromatic?
A: Yes, most B chromosomes are mainly or entirely heterochromatic.
Q: Do B chromosomes code for anything?
A: Most B chromosomes do not code for anything, but some contain sizeable euchromatic segments and do code for some products.
Q: How likely is it that B chromosomes would survive in a species unless there was some positive advantage?
A: It seems unlikely that supernumeraries would survive in a species unless there was some positive advantage.
Q: What has been identified as an advantage for B chromosomes in some cases?
A: In some cases, B chromosomes have been found to have positive advantages, such as in the British grasshopper Myrmeleotettix maculatus which has B chromosomes with a satellite DNA that occurs in warm, dry environments and is scarce or absent in humid, cooler places.
