Father's or Mother's gene. Which one will be expressed?
It has been long thought that (As in Mendelian genetics) parental origin of gene does not affect its expression. With respect to autosomal genes, male and female contribute equal number of genes and produce similar effects. But expression of some genes is significantly affected by the parental type, i.e. whether it came from male or female. This phenomenon is called Genomic Imprinting. One of the example of genomic imprinting is Igf2 (Insulin like growth factor II). It is present in both mice and humans and in both cases genomic imprinting takes place. A child inherit one allele from male parent and other allele from female parent. The paternal copy of Igf2 is actively expressed in the fetus and placenta but maternal copy remains completely silent. So, when the paternal copy is deleted in the mice, the mice produces small placenta and low weight baby. Another example would be Prader-Willi and Angelman syndromes. A child with Prader-Willi syndrome