Question

1. You are discussing with some of your bio major friends who have not taken Genetics and your non-bio major friends about how characteristics such as blue eye, light skin pigmentation, and light hair color, derived from a mutation that occurred about 10,000 years ago in Europe. Your friends are not very happy that you used the word mutation to describe the origin of human characteristics associated with light pigmentation. At that moment you only recall that green eye, fair skin and red hair in Neanderthals was due to other alleles and you mention that to them as an example of genetic determinants in species of the genus Homo. They are not convinced of your choice of the word mutation. Then you remember part of one of the papers that you read regarding the OCA2 allele.

“OCA2, homologous to the mouse pink-eyed dilution gene, encodes the human protein P, an integral membrane protein involved in both the transport of tyrosine and that helps in the regulation of intramelanosomal conditions. Mutations in OCA2 result in type II oculocutaneous albinism, but admixture mapping methods have also linked OCA2 with normal skin and eye pigment variation. In Europeans, SNP rs12913832, which locates within HERC2 gene, 21 kb upstream of the OCA2 promoter, has been shown to be involved in the regulation of OCA2 expression. The derived allele is significantly associated with European blue eye color and fair skin and hair color. A missense mutation (rs1800414, His615Arg) is a candidate variant for light skin pigmentation in East Asia, where it is found at high frequencies. However, this variant is absent in European and West African populations, thus providing evidence for alternative ways of depigmentation in Europeans, and consequently, of convergent evolution of light skin pigmentation in Europeans and East Asians.” (López S, Alonso S (2014) Evolution of skin pigmentation differences in humans, eLS. John Wiley & Sons, Ltd. DOI: 10.1002/9780470015902.a0021001.pub2.)

How can you use this piece of information to help you explain to your friends what is the significance of mutations in the emergence of new genetic properties (alleles) that may result (or not) in new phenotypic characteristics? (Recall that not all SNPs affect phenotype.)

Answer 1

first of all, all mutations will not emerge to new phenotypic properties and characteristics. there are specific alleles for specific traits and characters. for example , cry proteins are encoded by cry genes which helping to decrease insects. the majority of mutations are neutral in their effects on the organisms. mutations can be beneficial. as example, sickle cell anemia copies of genes have resistance towards malaria. only hereditary mutations. it will be passed to next generation. phenotypic characters are evolved . mutations occurring in the stretch of dna , protein coding region, etc... cause new phenotypic characters in an individual. snp can be change, silent the noncoding region. it influence the promoter activity, mrna conformation and subcellular localization and produce disease.