High School Blues Evan and Alexia had been happily married f

High School Blues Evan and Alexia had been happily married for seven years and had a delightful ve-year-old son named Ryan. One day, while going through his old high school biology textbook, Evan stumbled on some troubling information. In the section on the genetics of eye color, he read that two blue-eyed parents cannot produce a brown-eyed child. is was disturbing to him because both he and Alexia had blue eyes, but Ryan had brown eyes. He and Alexia were very much in love and Evan didn’t believe his wife had been unfaithful. Puzzled, he questioned his wife, who con rmed she had been faithful to him. Evan had known Alexia long enough to recognize when she was lying and detected nothing but honesty in her response.Assuming that Alexia has been faithful, suggest as many hypotheses as you can to explain Ryan’s phenotype.

question- assuming that alexia has been faithfull, suggest as many hypothesis as you can explain Ryan\'s pehotype?

Solution

It is a myth that eye colour is determined by a single gene, with the allele for blue eyes recessive to the allele for brown eyes. People without the understanding of its genetics think that two blue-eyed parents cannot have a brown-eyed child. This misleading idea was created by the study of Davenport and Davenport (1907) who classified the eye colour as simplex(light eye colours like blue) and duplex(dark eye colours). However, Follow-up studies from Holmes and Loomis (1909) said that eye colour varies continuously, and dividing it into categories is baseless.

With our current understanding, We can say that eye colour in humans is a polygenic trait and is controlled by many genes. Two genes on chromosome 15 (namely: OCA2 and HERC2 ) contribute majorly to the eye colour. Apart from that other genes (eg : ASIP, IRF4, SLC24A4, SLC24A5, SLC45A2, TPCN2, TYR, and TYRP1) are likely to act in combination to the alleles of OCA2 and HERC2 to produce different shades of eye colours in different people.

Hence, we can conclude that eye colour is determined by variation in several different genes and the interactions between them, and this makes it possible for two blue-eyed parents to have brown-eyed children.