Albinism is determined by a recessive gene in man. The presence of albinism in `50%` children born to a couple proves that :-

Options

A. Both parents are heterozygous for albinism
B. Father is homozygous normal and mother is heterozygous
C. Father is homozygous for albinism but mother is heterozygous
D. Both are homozygous

Answer

To solve the question regarding the inheritance of albinism, we need to analyze the genetic background of the parents and their offspring. Here’s a step-by-step breakdown:

### Step 1: Understand the Genetics of Albinism
Albinism is caused by a recessive gene. This means that an individual must inherit two copies of the recessive allele (let's denote it as 'a') to express the trait (i.e., be albino). The genotypes can be classified as follows:
- Homozygous dominant (AA): Normal pigmentation
- Heterozygous (Aa): Normal pigmentation (carrier)
- Homozygous recessive (aa): Albino

### Step 2: Analyze the Offspring Ratio
The question states that 50% of the children born to a couple are albino. This indicates that there is a specific genetic combination between the parents that leads to this ratio.

### Step 3: Determine Possible Parental Genotypes
To achieve a 50% occurrence of albinism in the offspring, we can set up a Punnett square. The possible combinations of parental genotypes that could lead to this outcome are:
1. One parent is homozygous recessive (aa) and the other is heterozygous (Aa).
2. Other combinations (like both parents being heterozygous) would not yield a 50% ratio of albino children.

### Step 4: Set Up the Punnett Square
If we assume:
- Parent 1 (Father): Homozygous for albinism (aa)
- Parent 2 (Mother): Heterozygous (Aa)

The Punnett square would look like this:

| | A | a |
|-------|-------|-------|
| **a** | Aa | aa |
| **a** | Aa | aa |

From this square, we see:
- 50% of the offspring (Aa) are carriers with normal pigmentation.
- 50% of the offspring (aa) are albino.

### Step 5: Conclusion
Since 50% of the children are albino, it confirms that one parent must be homozygous recessive (aa) for albinism, while the other parent must be heterozygous (Aa). Therefore, the presence of albinism in 50% of the children indicates that the father is homozygous for albinism and the mother is heterozygous.

### Final Answer
The presence of albinism in 50% of the children born to a couple proves that the father is homozygous for albinism (aa) and the mother is heterozygous (Aa).

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