You are a pet store owner and you have a specialty section for exotic guppies. I

Question

You are a pet store owner and you have a specialty section for exotic guppies. In it you have several unusual fish, and you have been able to define the genetics of these animals fairly well. You have found several unlinked genes with allele pairs

Long fins dominant to short fins; curly fins recessive to straight fins; blue is x-linked and dominant to yellow; googly eyes are recesive; purple stripes are dominant to no stripes.

a.) You have managed to create an All Heterozygous line that has long, straight fins, purple stripes and normal eyes. Females are heterozygous blue and males are yellow. You want to display for your customers all of the phenotypes that are available so you would like to make a tank containing fish that have Short, curly fins with no stripes and googly eyes with yellow females and blue males. If you cross your heterozygote line to itself and collect 1000 eggs, how many fish will you have for your tank? (please show all steps)

b.) You have a customer who requests a Blue male fish with normal eyes, short curly fins and purple stripes. How many of your 1000 eggs from a.) will fit his requirements?

Explanation / Answer

Cross is:-
Ll Ss Nn Pp XbXy (genotype of female)
       X
Ll Ss Nn Pp XyY (genotype of male)

32 gametes of female and 32 gametes of male will be obtained.

Total genotypes (or fertilised eggs) = 32*32=1024.
a) Required genotype= llssnnppXyXy (female)
Chances of having such a female=1/4*1/4*1/4*1/4*1/4 = 1/1024
Similarly,required genotype of male = llssnnppXbY
Chances of having it is 1/1024.

b) Customer is asking for genotype= llssN_P_XbY
Chances of having this genotype = 1/4*1/4*3/4*3/4*1/4 = 9/1024
So, around 9 fertilised eggs will have this combination

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