Genes for colour blindness in humans are carried by
A. abnormal sex
B. father
C. mother
D. none of the above

Options

A. A,C,D
B. A,B,C,D
C. B,C
D. A,B,C

Answer

To solve the question about which parent carries the genes for color blindness in humans, we can follow these steps:

### Step 1: Understand the Genetics of Color Blindness
Color blindness is primarily caused by a gene located on the X chromosome. It is an X-linked recessive trait, meaning that the gene responsible for color blindness is present on the X chromosome.

**Hint:** Remember that X-linked traits are associated with the X chromosome, which is significant in determining inheritance patterns.

### Step 2: Identify the Chromosomal Contribution of Parents
Humans have two sex chromosomes: females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). Since color blindness is X-linked, it can be passed from mothers to their sons or from fathers to their daughters.

**Hint:** Consider how the X and Y chromosomes are inherited from each parent.

### Step 3: Determine the Role of Each Parent
- **Mother (XX)**: A mother can pass on one of her two X chromosomes to her offspring. If she carries the color blindness gene on one of her X chromosomes, she can pass it to her son, making him color blind.
- **Father (XY)**: A father passes on his Y chromosome to his sons and his X chromosome to his daughters. If he has the color blindness gene on his X chromosome, he will pass it to his daughters, but not to his sons.

**Hint:** Think about how traits are passed from parents to children based on their sex chromosomes.

### Step 4: Conclusion
Since the gene for color blindness is carried on the X chromosome, and since mothers provide one of the X chromosomes to their sons, the correct answer to the question is that the genes for color blindness in humans are carried by the **mother**.

### Final Answer
C. mother