How many of the following diseases shows inheritance pattern similar to Mendelian factors ?
Cystic fibrosis , Klinefelter's syndrome, Haemophilia , Down's syndrome , Sickle cell anemia , Colour blindness , Turner's syndrome , Thalassemia , Phenylketonuria

Options

A. 4
B. 5
C. 6
D. 3

Answer

To determine how many of the listed diseases show an inheritance pattern similar to Mendelian factors, we will classify each disease based on whether it is a Mendelian disorder or a chromosomal disorder.

1. **Cystic Fibrosis**: This is an autosomal recessive disorder. It is caused by mutations in the CFTR gene. **(Mendelian disorder)**

2. **Klinefelter's Syndrome**: This is a chromosomal disorder characterized by the presence of an extra X chromosome in males (XXY). **(Chromosomal disorder)**

3. **Hemophilia**: This is a sex-linked recessive disorder caused by mutations in genes on the X chromosome. **(Mendelian disorder)**

4. **Down's Syndrome**: This is a chromosomal disorder caused by an extra copy of chromosome 21 (trisomy 21). **(Chromosomal disorder)**

5. **Sickle Cell Anemia**: This is an autosomal recessive disorder caused by a mutation in the HBB gene. **(Mendelian disorder)**

6. **Color Blindness**: This is a sex-linked recessive disorder caused by mutations in genes on the X chromosome. **(Mendelian disorder)**

7. **Turner's Syndrome**: This is a chromosomal disorder characterized by the absence of one X chromosome in females (45,X). **(Chromosomal disorder)**

8. **Thalassemia**: This is an autosomal recessive disorder caused by mutations in the genes that produce hemoglobin. **(Mendelian disorder)**

9. **Phenylketonuria (PKU)**: This is an autosomal recessive disorder caused by a deficiency in the enzyme phenylalanine hydroxylase. **(Mendelian disorder)**

Now, let's summarize the classification:
- Mendelian Disorders: Cystic Fibrosis, Hemophilia, Sickle Cell Anemia, Color Blindness, Thalassemia, Phenylketonuria
- Chromosomal Disorders: Klinefelter's Syndrome, Down's Syndrome, Turner's Syndrome

Counting the Mendelian disorders:
1. Cystic Fibrosis
2. Hemophilia
3. Sickle Cell Anemia
4. Color Blindness
5. Thalassemia
6. Phenylketonuria

Total Mendelian disorders = **6**

Thus, the answer is **6** diseases show an inheritance pattern similar to Mendelian factors.