What percentage of progenies when there is marriage between colourblind father's son and colourblind mother's daughter -

Options

A. 50% sons colour blind
B. 50% daughters carriers
C. 50% daughters normal
D. All of these

Answer

To solve the problem of determining the percentage of progeny from a marriage between a colorblind father's son and a colorblind mother's daughter, we will follow these steps:

### Step 1: Understand the Genetic Background
Colorblindness is an X-linked recessive trait. This means that the gene responsible for colorblindness is located on the X chromosome. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).

### Step 2: Determine the Genotypes
- The **colorblind father** has the genotype **XcY** (where Xc represents the X chromosome carrying the colorblind allele).
- The **colorblind mother** has the genotype **XXc** (she has one normal X chromosome and one X chromosome with the colorblind allele).

### Step 3: Identify the Gametes
- The **father's gametes** can be either **Xc** (colorblind X) or **Y** (male chromosome).
- The **mother's gametes** can be either **X** (normal X) or **Xc** (colorblind X).

### Step 4: Set Up the Punnett Square
We will create a Punnett square to visualize the possible combinations of gametes from the father and mother.

| | X (from mother) | Xc (from mother) |
|----------|------------------|-------------------|
| **Xc (from father)** | XcX (carrier female) | XcXc (colorblind female) |
| **Y (from father)** | XY (normal male) | XcY (colorblind male) |

### Step 5: Analyze the Progeny
From the Punnett square, we can see the possible genotypes of the progeny:
1. **XcX** - Carrier female (normal vision)
2. **XcXc** - Colorblind female
3. **XY** - Normal male
4. **XcY** - Colorblind male

### Step 6: Calculate the Percentages
From the results:
- 1 carrier female (XcX)
- 1 colorblind female (XcXc)
- 1 normal male (XY)
- 1 colorblind male (XcY)

This gives us a total of 4 progeny:
- 1 colorblind male (XcY)
- 1 colorblind female (XcXc)

Thus, the percentage of colorblind progeny (both males and females) is:
- Total colorblind progeny = 1 (colorblind male) + 1 (colorblind female) = 2
- Percentage of colorblind progeny = (2 colorblind progeny / 4 total progeny) * 100 = 50%

### Final Answer
The percentage of progeny that will be colorblind when there is a marriage between a colorblind father's son and a colorblind mother's daughter is **50%**.

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