A cross between AaBB X aa BB yields a genotypic ratio of :-

Options

A. 1 AaBB: 1 aaBB
B. 1 AaBB : 3 aaBB
C. 3AaBB: 1 aa BB
D. All AaBB

Answer

To solve the problem of finding the genotypic ratio from the cross AaBB × aaBB, we can follow these steps:

### Step 1: Identify the Parent Genotypes
The parent genotypes are:
- Parent 1: AaBB
- Parent 2: aaBB

### Step 2: Determine the Gametes
Next, we need to determine the possible gametes produced by each parent.
- For AaBB, the possible gametes are:
- AB (from A and B)
- aB (from a and B)

- For aaBB, the possible gametes are:
- aB (from a and B)

### Step 3: Set Up the Punnett Square
Now, we can set up a Punnett square to visualize the combinations of gametes from both parents.

| | aB | aB |
|---------|----------|----------|
| **AB** | AaBB | AaBB |
| **aB** | aaBB | aaBB |

### Step 4: Determine the Offspring Genotypes
From the Punnett square, we can see the resulting genotypes of the offspring:
1. AaBB
2. AaBB
3. aaBB
4. aaBB

### Step 5: Count the Genotypes
Now, we can count the occurrences of each genotype:
- AaBB: 2 occurrences
- aaBB: 2 occurrences

### Step 6: Write the Genotypic Ratio
The genotypic ratio can be expressed as:
- AaBB : aaBB = 2 : 2, which simplifies to 1 : 1.

### Final Answer
The genotypic ratio from the cross AaBB × aaBB is **1 : 1**.

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