Study the pedigree chart of a certain family | vedclass

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(C) The pedigree shows an affected father and an unaffected mother producing both affected and unaffected offspring. This pattern is consistent with a

Vedclass · Accepted Answer

The trait under study could not be colour blindness.

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(C) The pedigree shows an affected father and an unaffected mother producing both affected and unaffected offspring. This pattern is consistent with an autosomal dominant trait. Let the dominant allele be $A$ and the recessive allele be $a$. The affected father must be heterozygous $(Aa)$ because he has an unaffected son $(aa)$. The unaffected mother must be homozygous recessive $(aa)$. The cross is $Aa 	imes aa$. The offspring genotypes are $Aa$ (affected) and $aa$ (unaffected). Since the mother is $aa$,she contributes an $a$ allele to all children. The father contributes either $A$ or $a$. Therefore,the female parent is homozygous recessive $(aa)$,and the male parent is heterozygous $(Aa)$. Option $(A)$ is incorrect because the female parent is homozygous recessive. Option $(B)$ is incorrect because they can have a normal daughter $(aa)$. Option $(C)$ is correct because if the trait were colour blindness ($X$-linked recessive),an affected father would pass the trait to all his daughters,but here he has an unaffected daughter (if we assume the circle represents a daughter,though the pedigree shows two affected daughters and one unaffected son and one affected son). Actually,looking at the pedigree,the father is affected and the mother is unaffected. They have two affected daughters,one unaffected son,and one affected son. This is consistent with an autosomal dominant trait. If it were $X$-linked recessive,an affected father $(X^aY)$ and normal mother $(X^AX^A)$ would produce normal daughters $(X^AX^a)$ and normal sons $(X^AY)$. Thus,it cannot be $X$-linked recessive (colour blindness).

Study the pedigree chart of a certain family given below and select the correct conclusion which can be drawn for the character.

Similar Questions

In the provided pedigree,assume that no outsider marrying into the family carries the disease. Determine the genotypes of $C$ and $D$.

Which of the following disorders is not hereditary?

Red-green colour blindness appears due to

Which one is a sex-linked disease?

Quantitative defect of hemoglobin $- P$
Qualitative defect of hemoglobin $- Q$
Select the correct option for $P$ and $Q$.
$\quad \quad P\quad \quad \quad Q$

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