Question

The pedigree on the right shows the inheritance pattern for an X-linked recessive disorder.
How many individuals are carriers of the disease but are not affected?

Answer 1

Since, you haven't attached any image, we shall look at every possibility in brief.

Gene under consideration is a X linked recessive allele, the conditions in which it can express itself :

• In a pair of homozygous recessive alleles. (Incase of woman)
• In a genotype of the type : XY (Men)

Usually when females inherit a gene for sex linked recessive disorder, the latter is unable to express itself due to the presence of a pure X gene (dominant). They often end up as carriers.

Case 1 : Inherited from a carrier mother.

Let us assume she married an afflicted man. (X^c will be X chromosome)

$\begin{array}{|c|c|c|}\cline{1-3} & \sf X^c & \sf Y \\ \cline{1-3}\sf X^c & \sf X^cX^c & \sf X^cY \\ \cline{1-3}\sf X & \sf XX^c & \sf XY \\ \cline{1-3} \end{array}$

• A carrier female
• Affected male and female
• Normal male

In the case, 3 off springs inherit the gene but only one isn't affected.

Let us assume she married a normal man. (X chromosome)

$\begin{array}{|c|c|c|}\cline{1-3} & \sf X & \sf Y \\ \cline{1-3}\sf X^c & \sf XX^c & \sf X^cY \\ \cline{1-3}\sf X & \sf XX & \sf XY \\ \cline{1-3} \end{array}$

• A normal male and female
• A carrier female
• An affected male

Again, two off springs inherit the gene but only one isn't affected.

$\rule{300}{2}$

Case 2 : Inherited from an affected mother.

Let us assume she married an affected man.

$\begin{array}{|c|c|c|}\cline{1-3} & \sf X^c & \sf Y \\ \cline{1-3}\sf X^c & \sf X^cX^c & \sf X^cY \\ \cline{1-3}\sf X^c & \sf X^cX^c & \sf X^cY \\ \cline{1-3} \end{array}$

All the off springs are affected.

Let us assume she married a normal man.

$\begin{array}{|c|c|c|}\cline{1-3} & \sf X & \sf Y \\ \cline{1-3}\sf X^c & \sf XX^c & \sf X^cY \\ \cline{1-3}\sf X^c & \sf X^cX^c & \sf X^cY \\ \cline{1-3} \end{array}$

• Two affected males and one affected female.
• One carrier female

In the case, 4 off springs inherit the gene but only one isn't affected.

$\rule{300}{2}$

$\rule{300}{2}$

Answer 2

Answer:

4 and XaY

Explanation:

its right on edge 2020