Question

Sickle cell anemia is known to run in a family. A pedigree chart for this family is shown below.

The parents are shown at the top and from left to right appear as a half-shaded circle next to a half-shaded square. The two are connected by a straight line. Below the parent pair is a vertical straight line connecting to the next row of circles and squares which are the offspring. Starting from left an unshaded square, half-shaded circle, another half-shaded circle, and a completely shaded square are shown. All of these are also connected by a horizontal straight line.

What percentage of the offspring are carriers of the disease but do not have it?

Answer 1

50% are carriers since only two of the children represent 'half shaded'.

Step-by-step explanation:

Sickle cell anemia is an autosomal recessive disease therefore it can only go down a family under following conditions:

1. ONLY one of the parent is affected, thus 50% children will only be carriers and 50% will be clean.

2. Both parents are carriers, then 50% children will be carriers, 25% clean and 25% affected.

3. Both parents are affected, all children will definitely be affected.