You have found two isolated populations of mice inhabiting a frat house. One pop

Question

You have found two isolated populations of mice inhabiting a frat house. One population is in the basement cabinets of the frat house. This population exhibits grey fur, red eyes and short tail. The other population inhabits the stack of pizza boxes that the fraternity has been collecting and placing in the attic. This fraternity has taken pride in retaining pizza boxes for the past 25 years. The pizza box mouse strain has cheddar colored fur, pepperoni eyes, and a long stringy tail. Unbeknownst to the frat members, there is poor wiring throughout the structure which has resulted in isolation of the two populations (attic mice traveling through the wall to the basement, and cabinet mice going up the wall to the attic get shocked or are electrocuted).

Since the frat brothers, many of whom are athletes, are afraid of mice, they get the pre-vet majors to try and remove them from the fraternity house. The Pre-vets, full of scientific curiosity, decide to conduct a genetic study. They isolate the 2 strains and cross-mate males to females of the opposite population. The result is 35 mice with cheddar fur, red eyes with long stringy tails and 1 mouse with cheddar fur, red eyes and short tail. Assuming simple genetic inheritance, explain which traits are dominant and recessive and whether this inheritance follows Mendels laws of inheritance?

Assuming independent assortment, can a test cross be constructed next, using only the offspring of the true breeding cross that was done?

Assuming independent assortment, with respect to the eyes of the mice what is the probability of getting 5 pepperoni eyes and 1 red eyed mouse in any order vs the probability of getting 5 red eyes and 1 pepperoni eye in any order?

You conduct an F1 test cross using a mouse that had been identified to carry all three recessive traits. This cross yields 36 mice. What are the possible phenotypes of the offspring and their predicted ratios and offspring (out of 36) given independent assortment and the unknown F2 mice was heterozygous for all 3 traits?

Assume that you do an F1 cross and actually get the following results

cheddar fur mice with pepperoni eyes and long tails - 62
grey mice with pepperonis eyes and short tails – 7
grey mice with red eyes and long tails – 2
cheddar fur mice with red eyes and long tails – 5
grey mice with red eyes and short tails – 58
cheddar fur mice with pepperoni eyes and short tails -1

Conduct a linkage analysis to determine gene loci of these traits
Which traits are the most tightly linked?
Which traits have the greatest probability of being separated during a cross-over?

Explanation / Answer

It is a heterozygous chromosome that is it has one dominant allele and the recessive allele.

Pizza box mouse strain (Attic) is dominant and the Basement cabinet mouse strain is recessive.

Dominant traits - Cheddar fur, red eyes

Recessive trait - Long stringy tail, short tail, pepperoni eyes, grey fur

Mendel's second law is the Law of independent Assortment, during gamete formation the segregation of the alleles of one alllelic pair is independent of the segregation of the alleles of another allelic pair.

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