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 the next row of circles and squares which are the offspring. Starting from the left an unshaded square, half-shaded circle, another half-shaded circle and a completely shaded square are shown. All these are also connected by a horizontal straight line. What percentage of the offspring have sickle cell anemia? 0% 25% 50% 100%

Answer 1

Answer:

25%

Explanation:

From the description;

The parents: half shaded circle and square = heterozygous parents

The offspring:

unshaded square = homozygous normal

half shaded circle = heterozygous normal

half shaded circle = heterozygous normal

completely shaded square = affected (homozygous abnormal)

The unshaded and half shaded offspring are normal and do not have sickle cell anemia. The completely shaded square represents a male offspring with sickle cell anemia.

Out of 4 offspring, 1 is affected for sickle cell anemia. Hence the percentage of the offspring that have sickle cell anemia is 25%.

Answer 2

Answer:

25%

Explanation:

Generally in a pedigree charts, Circles are used to represent females in the charts, while squares for males.

To show the presence of an investigated diseases, the circle or square is painted black,

to show that the individual is a carrier the shape is painted half way.

while to indicate an individual who is normal for the inherited disorder, the shape is not shaded at all.

Therefore, in this scenario,

the un-shaded square is a normal male,not caring allele for SS.

 the half-shaded circle and square are carrier of  SS allele.

 the completely shaded square  male carries a sickle cell traits,he is   homozygote  recessive for the  allele, He must have inherited the traits from each of the heterozygote dominant genes of the parents  AS blood groups.

Based on the Mendelian  inheritance; this is 25%, since 4-offspring  were involved, assuming  each is 25%, then  1/4= 25/100.