Question

Consider two loci, A and B, at which multiple different alleles are present in the human population (i.e., A1, A2, A3, etc. and B1, B2, B3, etc.). The diploid genotypes of you, your mother, and your father are A3A6 B2B4, A3A4, B2B4, and A4A6 B2B6, respectively.

a. What is the haploid genotype you inherited from your mother’s egg?

b. What is the haploid genotype you inherited from your father’s sperm?

c. What are the haploid genotypes of the parental-type gametes that you could produce?

d. What are the haploid genotypes of the recombinant-type gametes that you could produce?

e. If you sample 100 of your gametes, and find that 51 have genotype A3B4 and 49 have genotype A6B2, what

can you conclude about the relative location of loci A and B in the human genome?

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Answer 1

My diploid genotype --> A3A6, B2B4
My mother's diploid genotype --> A3A4, B2B4
My father's diploid genotype --> A4A6 B2B6

a. What is the haploid genotype you inherited from your mother’s egg?

My mother's genotype for the A locus is A3A4 and my father's genotype for the A locus is A4A6. Thus, I inherited the A3 allele from my mother.

My mother's genotype for the B locus is B2B4 and my father's genotype for the B locus is B2B6. Thus, I inherited the B4 allele from my mother.

The haploid genotype inherited from my mother is A3 B4

b. What is the haploid genotype you inherited from your father’s sperm?

Since my genotype is A3A6, B2B4 and I inherited the haploid genotype A3 B4 from my mother, I inherited the A6 B2 haploid genotype from my father's sperm.

c. What are the haploid genotypes of the parental-type gametes that you could produce?

The parental type haploid genotypes I could produce are:

• A3 B4 (Maternal)
• A6 B2 (Paternal)

d. What are the haploid genotypes of the recombinant-type gametes that you could produce?

The recombinant haploid genotypes I could produce are:

• A3 B2
• A6 B4

e. If you sample 100 of your gametes, and find that 51 have genotype A3B4 and 49 have genotype A6B2, what can you conclude about the relative location of loci A and B in the human genome?

Since 100% of the gametes produced are of the Parental type, with 51% Maternal and 49% Paternal, there is no recombination occurring between these two loci, and they are not assorting independently. Thus they are linked on the same chromosome and are very close together.