You want to create a sparkly-eyed, zebra striped gecko double mutant, so you cro

Question

You want to create a sparkly-eyed, zebra striped gecko double mutant, so you cross 2 homozygous mutatants together to create F1 geckos that are heterozygous for both mutations. (Normal skin color is A and zebra print allele is a; assume the normal eye sheen allele is R and the sparkly eye allele is r).

You cross sibiling F1 geckos together to generate the F2 generation. Because you were an excellent genetics student, you recognize that this is essentially a dihybrid cross and determine that ~1/16th of the F2 geckos shoulf be sparkly-eyed, zebra striped double mutatant geckos. However, in the F2 generation, you observe: 207 normal geckos, 95 zebra-striped geckos, 96 sparkly-eyed geckos, 2 zebra-striped, sparkly-eyed geckos.

Questions:

A) What is the genotype of F1 gecko? ( I am assuming that it is Ar, since there are 207 normal geckos, and 2 striped, but I am not sure)

B) If this were a normal dihybrid cross and the eye-color and eye-shaped loci were unlinked how many geckos in the F2 generation would you expect in each phenotypic class (normal gecko, zebra-striped, sparkly-eyed and zebra-striped, sparkly-eyed0.

C) Use a chi-square to determine if the difference between the observed and expected results are due to chance or something else? formula: (observed-expected)^2 / expected. (So for the observed is the number 400? Becuase of 207+95+96+2? and how do you find the expected? If I can get help to find the number for observe and expected, I can solve the rest, thank you.)

D) Why was only a single zebra-striped, sparkly-eyed gecko observed? (I am just asking in general, is it becuase the genotype for the striped and sparkly eye recessive?)

E) If two nomral geckos from F2 generation were crossed, what phenotypes in approximate proportions will you observe in (F3) progeny? (I do not even know where to begin, please help)

I can seriously need with these questions, I have an exam this Friday in a Genetics class, please help me understand this. Thank you!!

Explanation / Answer

Genotype of F1 will be AaRr (as it is dihybrid cross 2 types of genes were involved, assume that A determine one character and R represents other each character will be coded by two alleles) 1:2:1:2:4:2:1:2:1, you can calculate by using the above calculation you can know, as the charecters are not mentioned I cannot give the exact details. By the above data given the expected should be 198:96:96:10 and observed is 207:95:96:2. Based upon this we can determine by using mentioned formula. That is observed due to presence of two mutant alleles with genotype aarr.

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.