Question

Find out the frequency of $AabbCcDdee$ if parents are$AabbCCddEe$ and$AabbccDdee$
A. $0.78\%$
B. $12.5\%$
C. $25\%$
D. $50\%$

Answer 1

There are certain characters or traits that are controlled by several genes. If a particular character is controlled by three or more genes, they are called polygenic traits and the inheritance is called polygenic inheritance.

Complete answer:
Based on the principle of independent assortment, members of different allelic pairs behave as independent units. So naturally, when they are assorted into the gametes, their distribution will be independent of each other. Based on this principle, we can assess the probability of each character to be assorted to a gamete separately.
-In the first case, both the parents have $Aa$ in their genotype.
So, during gamete formation, gametes from each parent would be $A$ and $a$.
$Aa \times Aa$
So the progenies would be:
$AA,Aa,Aa$and $aa$.
So, $0.5$of the progenies will have $Aa$.
-As both parents have $bb$ in their genotype, all progenies will have $bb$.
So, the probability of having $bb$ in genotype in offsprings will be $1$.
-In the third case, one parent has $CC$ and the other has $cc$ in their genotype.
$CC \times cc$
All progenies will have $Cc$ in their genotype. So, the probability is again $1$.
-In the fourth case, it is
$dd \times Dd$
Progenies will be $Dd,dd,Dd,dd$.
Dd will have a probability of$0.5$
-In the last case, it is
$Ee \times ee$
Progenies will be $Ee,Ee,ee,ee$
So again, the probability for ee is $0.5$
So in order to get the probability of offsprings having the genotype $AabbCcDdee$, we have to multiply the probabilities.
So the answer will be $0.5 \times 0.5 \times 0.5 = 0.125$
Hence the correct option is B.

Note: For studying polygenic inheritance, the perfect example is human skin colour. Our skin colour is determined by a group of genes. If all of the alleles are dominant, then the colour will be darkest and if all of them are recessive, the person will have the lightest skin colour.