Question

What is the probability distribution of offspring genotypes resulting from a cross between two parents with specific genotypes?

Answer 1

To determine the probability distribution of offspring genotypes resulting from a cross between two parents, we typically use a Punnett square. The specific genotypes of the parents will dictate the possible combinations of alleles in their offspring.

Let's use a general example to illustrate how to do this:

### Example Cross
Assume we have two parents with the following genotypes:

- Parent 1: Aa (heterozygous)
- Parent 2: Aa (heterozygous)

### Step 1: Determine Alleles
Each parent can contribute one of two alleles (A or a). If we label the alleles as follows:

- A = dominant allele
- a = recessive allele

### Step 2: Set Up a Punnett Square
The Punnett square for this cross would look like this:

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

### Step 3: Determine Offspring Genotypes
From the Punnett square, we can see the possible genotypes of the offspring:

1. AA (homozygous dominant)
2. Aa (heterozygous)
3. Aa (heterozygous)
4. aa (homozygous recessive)

### Step 4: Calculate Probabilities
Now, we count the occurrences of each genotype:

- **AA**: 1
- **Aa**: 2
- **aa**: 1

Total offspring = 4

So, the probabilities for each genotype are:

- P(AA) = 1/4 = 0.25
- P(Aa) = 2/4 = 0.50
- P(aa) = 1/4 = 0.25

### Conclusion
In this example, the probability distribution of offspring genotypes from a cross between two heterozygous parents (Aa x Aa) is:

- 25% AA
- 50% Aa
- 25% aa

### General Method
You can use the same method for any parental genotype combinations by adjusting the alleles accordingly and constructing a Punnett square to find the ratios of the possible genotypes.