A and B genes are linked. What shall be the genotype of progeny in a cross between `AB//ab` and `ab//ab`?

Options

A. AABB and aabb
B. AaBb and aabb
C. Aabb and aaBB
D. AaBb and AaBb

Answer

To determine the genotype of the progeny from a cross between `AB//ab` and `ab//ab`, we can follow these steps:

### Step 1: Identify the Parental Genotypes
The parental genotypes are:
- Parent 1: `AB` (heterozygous for both traits)
- Parent 2: `ab` (homozygous recessive for both traits)

### Step 2: Determine the Gametes Produced
Since the genes A and B are linked, the gametes produced by the first parent (`AB`) will be:
- `AB` (parental type)
- `ab` (parental type)

The second parent (`ab`) can only produce:
- `ab` (parental type)

### Step 3: Set Up the Punnett Square
We can set up a Punnett square to visualize the possible genotypes of the progeny. The gametes from Parent 1 will be placed on the top, and the gametes from Parent 2 will be placed on the side:

```
ab
--------
| AB | ab |
--------
```

### Step 4: Fill in the Punnett Square
Now, we fill in the Punnett square by combining the gametes:

- From `AB` (Parent 1) and `ab` (Parent 2) → `AB`
- From `ab` (Parent 1) and `ab` (Parent 2) → `ab`

So the filled Punnett square looks like this:

```
ab
--------
| AB | ab |
--------
```

### Step 5: Determine the Genotypes of Progeny
From the Punnett square, we see that the possible genotypes of the progeny are:
- `AB` (1 occurrence)
- `ab` (1 occurrence)

### Conclusion
The genotypes of the progeny from the cross between `AB//ab` and `ab//ab` are:
- 50% `AB`
- 50% `ab`