Question

You will determine which alleles your person has for four different genes by flipping coins. Heads is dominant, tails recessive. Your person must have two alleles for all four types of genes! In other words, you will flip eight coins to make the genotype. From this genotype, you will figure out the phenotype of your person.

The traits are:

Albinism (no pigment in skin or hair)— Dominant A allele codes for normal coloration, recessive a allele codes for albinism.

Brachydactyly (short fingers and toes)—Dominant B allele codes for short fingers, recessive b allele codes for normal fingers.

Freckles— Dominant F allele codes for presence of freckles, recessive f allele codes for no freckles.

Polydactyly (extra fingers and toes)— Dominant P allele codes for extra fingers, recessive p allele codes for five fingers

1. How might the expression of one of these genes determine whether another gene can expressed (e.g. affect the phenotype)? Which genes would be involved in this epistasis?

For example, to make a person, he/she would have two alleles for albinism, two alleles for brachydactyly, two alleles for freckles and two alleles for polydactyly. Based on this genotype and an understanding of dominant and recessive traits, you could determine their phenotype.

1. What genotype does your person have?

2. What phenotype does your person have?

Answer 1

The question here is to flip coins and select a genotype and phenotype of a person for the given characters – Albinism, Brachydactyly, Freckles and Polydactyly.

Upon flipping the coin eight times, the alleles that I determined for each of these characters are as follows:

CHARACTER	COIN SIDE	TRAIT	GENOTYPE
Albinism	Heads	Dominant	Aa
Tails	Recessive
Brachydactyly	Tails	Recessive	bb
Tails	Recessive
Freckles	Heads	Dominant	FF
Heads	Dominant
Polydactyly	Heads	Dominant	Pp
Tails	Recessive

The genotype of the individual that we obtained by flipping coins is AabbFFPp.

The phenotype of this genotype will be normal skin colour with freckles and polydactyly with normal fingers.

Epistasis is a phenomenon in which one gene masks the expression of another gene. The gene for Albinism is epistatic in nature. The presence of two recessive alleles for albinism will lead to lack of pigmentation regardless of the presence of pigment producing genes in the other loci.