Question

6) Suppose a diploid organism contains the chromosomes A*B$C and a*b$c (homologs of chromosome 2), and also the chromosomes D$E*F, and d$e*f (homologs of chromosome 11. ($ represents a repetitive region of DNA that is prone to recombination, while * represents the centromere). What normal gametes is chromosome 2 capable of producing (assuming no linkage)?

a) Assuming the gametes created for each chromosome are independent of each other (remembering that a normal cell gets a normal version of chromosome 2 AND a normal version of chromosome 11), how many types of normal gametes could be produced by this cell in total, with respect to chromosome 2 and chromosome 11?

b) If crossing over occurs in the repetitive region of chromosome 11 and creates recombinant gametes 36 percent of the time, and no other recombination occurs, what gametes will be produced and in what abundances with respect to chromosome 11?

Answer 1

Chromosome 2 homologs: ABC and abc
Chromosome 11 homologs: DEF and def

Gametes produced by chromosome 2: ABC, ABc, AbC, aBC, Abc, aBc, abC, abc
Gametes produced by chromosome 11: DEF, DEf, DeF, aEF, Def, dEf, deF, def

The overall genotype of the organism with respect to both the chromosomes: AaBbCcDdEeFf
The formula for calculating the number of different types of gametes produced = 2n
n = Number of heterozygous combinations
In the given case,
n = 6
The number of different types of gametes produced = 26
= 64