Mice are normally solid colored, but there are many different true-breeding stra
ID: 98784 • Letter: M
Question
Mice are normally solid colored, but there are many different true-breeding strains of mouse that have the phenotype of white spots. In these mice, white spotted is recessive to solid color. Below are the results from performing a complementation test between 6 different white spotted mouse strains. The phenotype of each hybrid is indicated by the symbols in the boxe, and a"+" indicates that the hybrid was wild type (solid) colored and a"-" indicates the hybrid has the mutant spotted phenotype.
A. Put the strains into groups that have mutations in the same gene i.e complementary groups
In mice it is possible to make a targeted mutation in any gene if you have the DNA for that gene. These are referred to as "knockout mice". A scientist studing the gene Pax made a homozygous pax/pax knockout mouse and found that it had white spots and that its white spotted phenotype was recessive to wild type. She then crosses this knockout mouse with each of the 6 strains listed above and obtained the following results:
B. Which of the 6 mutant strains have a mutation in the Pax gene? (It is not strain 1 for sure)
Strain 1 Strain 2 Strain 3 Strain 4 Strain 5 Strain 6 Strain 1 - + + + - + Strain 2 - + - + + Strain 3 - + + - Strain 4 - + + Strain 5 - +Explanation / Answer
A.strain 4 and strain 2,strain 5and strain 1,strain 6 and strain3 are complimentary groups hence producing recessive progeny.
B.stain 2 strain 4 have mutation in the pax gene as when they were crossed with pax knockout mouse they produce spotted ( recessive gene)progeny