Andrés Barboza, a Ph.D. student working alongside Texas A&M associate professor Dr. Heath Blackmon at the Blackmon Lab in the Biology department at Texas A&M University, recently published his findings on potential explanations for achiasmy, the lack of genetic crossing for one or both sex chromosomes, in G3: Genes, Genomes and Genetics.
Barboza developed and tested two models which simulate popular hypotheses for explaining the origin and evolution of achiasmy, trying to find why some organisms, such as fruit flies and silkworms, reproductive systems feature it as part of the reproductive process and not as a defect or error of genetic recombination.
The first model is an old hypothesis known as the “sexual antagonism and pleiotropy hypothesis,” which explains that in some instances, genetic recombination can be damaging between sex chromosomes. By stopping recombination, the chromosomes preserve genes and prevent them from harming each other during recombination . The second hypothesis is more recent and developed by Blackmon. His “fragile Y” hypothesis suggests that because of sex chromosomes size differences, crossovers can misalign and cause catastrophic errors such as faulty chromosome separation or degradation or loss of sex-linked genes. Achiasmy acts as a safeguard.
Barboza’s comparison of both models led to a conclusion that suggests the reasons for achiasmy change with a sex chromosome’s age, opening further discussions about previously existing academic theories and providing an explanation as to why some species develop achiasmy despite the advantages of genetic recombination. This marks a significant advancement in the understanding of biology and provides answers to an unsolved mystery within the field.
This work was funded by the National Institute of General Medical Sciences, National Institutes of Health grant R35 GM138098 to H.B.