Blond Solomon Islanders have a different mutation responsible for their hair col
ID: 179495 • Letter: B
Question
Blond Solomon Islanders have a different mutation responsible for their hair color. The version of the TYRP1 hair color gene (allele) for dark hair has a C at position 277 of the coding sequence of tyrosinase-related protein 1 while the TYRP1 allele for blond hair has a T. People have 2 copies of the TYRP1 gene: one allele from their mother and one allele from their father. Thus three genotypes are expected in the Solomon Islands: CC (each allele has a C at position 277), CT (one allele with C, one with T), and TT (both alleles have T at position 277). Hair color for people of all three genotypes was measured with a spectrometer by collecting hair samples and determining the amount of reflectance of light at a particular wavelength. Data were plotted in a box graph which shows the distribution of all data points from high reflectance to low reflectance (see the right side of the figure to see how to read the box graph).
Based on the graph above, what color do most people with the CT genotype have?
Dark
Blond
A)Dark
B)Blond
CC CT TT How to read a box graph maximum 4th quartile median 3rd quartile 2nd quartile 1st quartile minimumExplanation / Answer
The CT genotype is heterozygous. The dark hair encoding allele C is dominant over blond hair encoding allele T. In heterozygous condition, the dominant allele always masks the effect of recessive allele and hence, the genotype expressed is dominant. Moreover, the genotype CT produced median range of reflectance in the above shown graph and is near to maximum than to minimum reflectance . Therefore, the people with genotype CT posess dark hair. Option A is correct.