Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino

Options

A. `50%`
B. `75%`
C. `100%`
D. `25%`

Answer

To solve the question regarding the probability of the second child being an albino, we can follow these steps:

### Step 1: Understand the Genetics of Albinism
Albinism is caused by an autosomal recessive mutation. This means that an individual must inherit two copies of the recessive allele (let's denote it as "a") to express the albino phenotype. The normal pigmentation allele can be denoted as "A".

### Step 2: Determine the Genotypes of the Parents
The couple has normal skin pigmentation, but they have produced an albino child. This indicates that both parents must be carriers of the recessive allele. Therefore, their genotypes must be heterozygous (Aa), where "A" is the normal allele and "a" is the albino allele.

### Step 3: Set Up the Punnett Square
To find the probability of their second child being an albino, we can set up a Punnett square for the cross between two heterozygous parents (Aa x Aa).

```
A a
----------------
A | AA | Aa |
----------------
a | Aa | aa |
----------------
```

### Step 4: Analyze the Punnett Square
From the Punnett square, we can see the possible genotypes of the offspring:
- 1 AA (normal)
- 2 Aa (normal carriers)
- 1 aa (albino)

This gives us a total of 4 possible outcomes:
- 3 out of 4 (75%) are normal (AA or Aa)
- 1 out of 4 (25%) is albino (aa)

### Step 5: Conclusion
The probability that their second child will also be an albino is 25%.

### Final Answer
The probability that their second child will also be an albino is **25%**.

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