The figure below is from Ferrari et al. (2014, Apidologie) and shows integument

Question

The figure below is from Ferrari et al. (2014, Apidologie) and shows integument (outer layer) color variation in the orchid bee Euglossa iopoecila at four sample sites (A-D) Green morph Blue morph 1. Suppose integument color is controlled by one locus with two alleles. Which sample site(s) are polymorphic and which are fixed for alleles causing color variation? (1 pts) a. b. Are the alleles interacting in a dominant/recessive or codominant way? (1 pt) Suppose we sample population B and we find 240 bees that are green, 170 that are blue, and 40 that are aquamarine 2. a. What are the allele frequencies at the color locus in the population? (2 pts) b. If this population randomly mates for one generation, what will be the genotypic frequencies? (2 pts)

Explanation / Answer

1. Polymorphism occurs when two or more variants of a gene or gene marker exist with each form being too common in a population to be merely attributable to a new mutation.

Allele fixation occurs when the frequency of one of the allele reaches 0 and is permanently eliminated from the population. Therefore, the other allele becomes fixed and all individuals in the population will be homozygous for that allele.

a) Sample sites B and C are polymorphic and sites A and D are fixed for alleles causing color variation.

b) The alleles are interacting in a codominant way as site B has intermediate bees are aquamarine.

2. Allele frequency = No. of copies of an allele in a population / Total no. of all alleles for that gene in a population.

Genotype frequency = No. of individuals with a particular genotype in a population / Total no. of individuals in a population.

Also, (Genotype frequency) = (Allele frequency)2

Let "p" denote the allele frequency for blue color (BB) and "q" denote the allele frequency of green color (GG).

Since both the alleles are codominant, we can denote them by different alphabets.

Suppose, the genotype frequency of blue colored bees, BB = p2

genotype frequency of green colored bees, GG = q2

and genotype frequency of aquamarine colored bees, BG = 2pq.

a) Allele freq. of blue color, p = 40 + 2 (170) / 2 (240) + 2 (170) + 2(40)

p = 380 / 900 = 0.42

Allele freq. of green color, q = 40 + 2 (240) / 2 (240) + 2 (170) + 2(40)

q = 520 / 900 = 0.58

b) Adding both allele frequencies, p + q = 0.42 + 0.58 = 1

This implies that the popualtion is in Hardy-Weinberg Equilibrium.

Even if this population randomly mates for one generation, the genotype frequencies will remain the same.

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