QUESTION 11 Color variation in weevils is controlled by a single autosomal locus

Question

QUESTION 11 Color variation in weevils is controlled by a single autosomal locus with multiple alleles. The alleles exhibit a dominance hierarchy, with red (R) dominant over all other alleles, black (Rb) dominant over white (RW) and tan (r), white dominant over tan, and tan recessive to all others (R>Rb>RW>r). In addition, expression of this gene is sex-limited to females: males carry color genes, but are always tan regardless of their genotype. A cross was set up between a white female and a tan male. The offspring consisted of 13 red females, 6 white females, 5 tan females, and 19 tan males. A. (2 pts) What were the genotypes of the parents in this cross? B. (4 pts) What are the possible genotypes of the daughters in this cross? Include all possible genotypes. C.(1 pt) Why do all of the sons have a tan phenotype? TTI Arial 3(12pt) ::T·-·-·?- : Cliek Save and Submit to save and se. Clek Save All Save All Answers Save and Submit MacBoo

Explanation / Answer

A] From the given information we can deduce that the parents have the following genotypes --

Mother's genotype -- R^w r [ Reason- the female is white coloured so it will have R^w allele and not R or R^b allele because these two alleles are dominant over R^w. It will contain one r allele because among the progeny there are 5 tan females and their genotype has to be

rr, otherwise they would show colour].

Father's genotype-- Rr [ Among the progeny, there are 13 red females. They have inherited the R allele from

their father as the mother is white in colour]

B] The possible genotypes for the daughters can be -- Rr [ red phenotype]

R^w r [ white phenotype]

r r [ tan phenotype]

C] The expression of colour is sex-limited, which means only the females show colour in their phenotypes. Males may be carriers of genes for different colours but these are not expressed in their phenotypes. So, whatever the genotype of the male weevils, they are always tan coloured.

  

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