Consider two different antigens on red blood cells of wild type mice according t
ID: 91352 • Letter: C
Question
Consider two different antigens on red blood cells of wild type mice according to the pathway shown. All 3 genes are autosomal recessives and are unlinked. Two different true breeding mice have been isolated that do not make antigen 1 or antigen 2 (both antigens are missing in each of these mice). A cross of these two mice produce F1 mice that make both antigens. What is the genotypes of the two parents Two of the F1 mice are crossed to one another. The possible phenotypes of the F2 are show. The proportions of one class of the F2 are shown. Calculate the proportion of the remaining F2 classes. Antigen l + antigen2 + Antigen l + antigen2 - Antigen l - antigen 2+ Antigen 1 - antigen2 - In mammals, X-chromosome dosage compensation is achieved by the inactivation of one of the two X chromosomes in females. (The genes on the X-chromosomes in males are always fully active). In eutherian mammals (mice, chimps, undergrads), the inactivation process in females is random and cells inactivate either the paternally derived or the maternally chromosome with equal probability. In contrast, in female marsupials (opossum, kangaroo), all cell inactive the same X-chromosome and the inactive X-chromosome is always derived from the same parent.Explanation / Answer
7. The genotype of one parent must be heterozygous and the other would be homozygous recessive.
In independent segregation, among the F2 progeny, the most frequent phenotype antigen1+ antigen 2+ is 27/64;
then antigen1+ antigen 2- would be 9/64; antigen 1- antigen 2+ would be 3/64; and antigen 1- antigen 2- would be 1/64.
8. The paternal X is inactivated in the two pedigrees shown