1. The Igf2 gene is autosomal and maternally imprinted. Imprinting was discovere
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Question
1. The Igf2 gene is autosomal and maternally imprinted. Imprinting was discovered at this locus from studies of the transmission of the deletion (del) of this gene in mice A) Using the parent crosses below indicate the genotype of the progeny in column 1. Given that lgf2 plays a role in growth before birth, in column 2 indicate the phenotype of the mice; state "normal-size", "small-size", or "?" (unknown) Cross: del / Igf2) female (Igf2 / Igf2) male x Progeny: Column 1 (genotype) 1. 2. Column 2 (phenotype) 1. 2. B) Explain why you observe those phenotypesExplanation / Answer
The igf2 is maternally imprinted. This means that if the gene is inherited from mother then it will not be expressed. So for the igf2 to be active it has to be given by the father.
1. (del/igf2) female x igf2/igf2)
The gametes are: del igf2 x igf2
Coulumn 1 Column 2
del/igf2 normal size
igf2/ig2 normal size
The gene is maternally imprinted. Hence the del mutant from mother will not have ay effect on the progeny as long as it has normal allele from father. The second progeny has recived a normal allele from father and hence we get normal heght.
C)
Progeny:
--+-- m --+-- m
--+--p --(-)--p
D) The first progeny has both normal alleles from parents. It will be of normal height. The second progeny has one 'del' mutant allele from father and normal allele from mother. Since the gene is maternally imprinted, the second progeny will not get benifit of the maternal + allele. Hence it will be of normal height.
E) The imrintng is an active chromosome silencing mechanism. if it is maternally imprinted, it will not be active if recieved from female. In the sperm the allele will be active and not imprinted. If the son has one allele which came from his mother, then it will continue to be imprinted.
The gametes from the shown crosses are:
Daughter: --+--m (imprinted) and --+--p (active)
son: --+--m (imprinted) and --+--p (active)
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