Question

It was previously known that early humans interbred with Neandertals and Denisovans. The researchers cited above used artificial intelligence to determine that early humans also interbred with a 3^rd related species for which there is no fossil evidence. In all three cases, evidence for genetic introgression (moving genes from one species to another) is based on remnants of genomes that remain behind: The hybrid individuals (half human, half non-human), long after the interbreeding events, repeatedly backcross with the larger human population. After repeated backcrossing, most of the non-human genome is removed from the human population. A few key genes remain, either introducing new alleles for corresponding genes in the human population or adding new genes that didn’t previously exist in humans. So, what does this process have to do with genetic linkage (and crossing over)? Also, speculate on the role that evolution might have played in determining which alleles or genes ended up in the human population by introgression from these three species.

Answer 1

Genes that are situated on the same chromosome are said to be linked genes. The crossing-over takes place when the two homologous chromosomes exchange their genetic material at meiosis I stage. The closer together the two genes are on a chromosome, the less probable their alleles will be alienated by crossing-over.

Linkage makes sure to maintain the genes in a chromosome to come into together. The crossing over makes possible the partition of genes present in a chromosome and separates into different gametes. The potency of linkage among two genes is inversely proportional to the space between them in the chromosome.

The evolution of the genome is determined by a complex interaction of factors, including selection, introgression, and recombination. The introgression is an essential resource of genetic variation in a population and might contribute to adaptation or adaptive radiation.

The evolutionary process can carry variants at a higher frequency than the de novo mutations, as long as the linked blocks of sequence with various functional mutations, potentially counting co-adapted alleles. This procedure is called adaptive introgression and it has increased to a distinction based on a sequence of high profile examples of human genomes.