Question

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DUE TODAY
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

Based on the pedigree chart provided, we can determine the genotype of each family member and their likelihood of passing on the sickle cell trait.

The half-shaded circle and half-shaded square represent carriers of the sickle cell trait (heterozygous individuals), while the completely shaded square represents an individual who has sickle cell anemia (homozygous recessive).

Since the father is completely shaded, he must be homozygous recessive (ss). The mother must be a carrier (Ss) because she is half-shaded.

When we consider the offspring, we can use a Punnett square to calculate the probability of each possible genotype.

| | S | s |
|---|---|---|
| S | SS | Ss |
| s | Ss | ss |

The offspring are:

- Unshaded square: SS (homozygous dominant)
- Half-shaded circle: Ss (heterozygous carrier)
- Half-shaded circle: Ss (heterozygous carrier)
- Completely shaded square: ss (homozygous recessive)

Therefore, 1 out of 4 offspring (25%) has sickle cell anemia (ss genotype), while the other 3 offspring are carriers of the sickle cell trait (Ss genotype).

So the answer is 25%. and