Can you please explain how they got these answers? 11 cont. A pedigree involving
ID: 190162 • Letter: C
Question
Can you please explain how they got these answers?
11 cont. A pedigree involving the Igf2 locus is shown below. Dwarf-sized individuals are indicated by solid square or circle 4 3 2 It is also known that female mouse 3 is homozygous for lgf2* allele. Based on this, please answer the following questions: a. What is the genotype of mouse 5 with respect to the lgf2 locus (2 points)? Igf2*/lgf2 b. What is the genotype of mouse 4 with respect to the lgf2 locus (2 points)? If male 1 is crossed with female 2, what is the probability that the first offspring is a dwarf-sized mouse (2 points)? c. 0Explanation / Answer
lgf2 gene in mice shows maternal imprinting. this means the allelle of the gene obtained from mother will remain transcriptionally silent while only the father allele will be active. Mice that will inherit the deletion chromosome from the paternal side will be small,but mice inheriting the same deletion from the maternal side will be normal.Thus, a deletion of Igf2 only causes a mutant phenotype when transmitted by the father.
a. the genotype of mouse 5 is lgf2+/lgf2-. The mother is a dwarf (balckened circle, so genotype, lgf2-/lgf2-). Now for the son to be dwarf as well he should recieve one copy of lgf2- from his father as then only he will be dwarf. . But the father is normal size i.e., hetrozygous for the trait. Therefore his genotype is lgf2+/lgf2-, Please understand that this is not sex-linked inheritance, it is simple autosomal inheritance.
b. The mouse 4 is dwarf. He has one copy of lgf2- gene from his father just like his mother has acquired one from her father. This means he is also heterogygous, lgf2+/lgf2-.
c. Both 1 and 2 have maternal copy og lgf2-, which explains why they are normal size, therefore when they have a child, the lgf2- will remain unexpressed and the first child cannot be a dwarf-sized mouse.