What ratio is expected in offsprings if father is colour blind and mother's father was colour blind :-

Options

A. `50%` daughter - colour blind
B. All the sons are colour blind
C. one daughter and one son colour blind
D. All the sons are normal

Answer

To solve the question regarding the expected ratio of offspring when the father is color blind and the mother's father was also color blind, we will follow these steps:

### Step 1: Understand the Genetics of Color Blindness
Color blindness is an X-linked recessive trait. This means that the gene responsible for color blindness is located on the X chromosome, and two copies of the mutated gene (homozygous condition) are required for females to be affected. Males, having only one X chromosome, will be affected if their single X chromosome carries the mutation.

### Step 2: Determine the Genotypes of the Parents
- **Father (Color Blind)**: He has the genotype X^cY (where X^c represents the X chromosome with the color blindness allele).
- **Mother**: Her father was color blind, which means she must be a carrier (X^cX) because she has one normal X chromosome (X) and one X chromosome with the color blindness allele (X^c).

### Step 3: Set Up a Punnett Square
We will set up a Punnett square to determine the possible genotypes of the offspring from these parents.

- **Father's Alleles**: X^cY
- **Mother's Alleles**: X^cX

The possible combinations from the Punnett square are:
- X^c from the mother and X^c from the father → X^cX^c (affected female)
- X from the mother and X^c from the father → X^cX (carrier female)
- X^c from the mother and Y from the father → X^cY (affected male)
- X from the mother and Y from the father → XY (normal male)

### Step 4: Analyze the Offspring Ratios
From the Punnett square, we have the following possible offspring:
1. X^cX^c (affected female) - 1
2. X^cX (carrier female) - 1
3. X^cY (affected male) - 1
4. XY (normal male) - 1

This gives us a total of:
- 1 affected female (X^cX^c)
- 1 carrier female (X^cX)
- 1 affected male (X^cY)
- 1 normal male (XY)

### Step 5: Calculate the Ratios
The expected ratio of the offspring is:
- 1 affected female : 1 carrier female : 1 affected male : 1 normal male

This can be simplified to:
- 1:1:1:1

### Conclusion
The expected ratio of offspring when the father is color blind and the mother's father was also color blind is 1 affected female : 1 carrier female : 1 affected male : 1 normal male.