Question

Include all the information below about Blonde hair (Melanesia vs. Europe) : ( its genetic mutation(s), and the evolutionary mechanisms via which your trait came to differ between populations)

What is the trait called colloquially and scientifically?

What are the hallmarks or characteristics? ?

What mutation(s) causes the trait in your population of interest?

Name of allele? Gene? Type of mutation? ?

What are the differences in frequencies of your trait between the two populations, or, which alleles are characteristic of each population? ?

Are there aspects of this trait that could alter the fitness of the population?

Was the trait selected for or against? What about the environment caused this selection? ?

Did migration, bottlenecking, or the founder effect play pivotal roles in the prevalence of your trait? ?

Were there any types of selective breeding that contributed to the difference in frequency between populations. ?

Is there evidence that interactions with other, pre-existing genes, played a role in the emergence or extinction of your trait within each population?

Answer 1

Blonde hair is most exclusively found phenotype in Europians. Melanesians have the darkest skin but 5 to 10% of them atre blondes. This shows the highest occurence of blonde hair outside the europe.

It has found that, a genetic mutation is responsible for blonde hair in Melanesians. Melanin pigment synthesis is responsible for skin/hair/eye color. Tyrosinase is the enzyme which is essential for melanin synthesis. Now, researchers have identified that Melanesians blonde carry a recessive mutation in gene encoding TYRP-1 (tyrosinase related protein -1 ) which is involved in melanin synthesis. This single nucleotide change, mis-sense mutation, known as R93C, changes aminoacid residue from arginine to cysteine which decreases stabiliy and function of tyrosinase enzyme.

As, this is recessive mutation, Melanesian blondes carry 2 copies of this mutant gene, each from both the parents. This novel mutation is at frequency of 26% which represents large genetic drift. This is one of the best example which shows strong influence of genetic drift and local positive selection in population.