Question

Study the following statements and pick up the incorrect statements.
I. Haemophilia is an X-linked disorder due to dominant genes.
II. Inheritance of colour blindness follows the cris-cross pattern.
III. Haemophilia A and Haemophilia C are X-linked disorders.
IV. Y-linked genes are called holandric genes.

• A. I, II
• B. III, IV
• C. II, IV
• D. I, III

Hint:

Remember common genetic disorders and inheritance patterns: \textbf{X-linked recessive disorders:} Haemophilia A, Haemophilia B, Colour blindness. These show criss-cross inheritance. \textbf{Autosomal recessive disorders:} Haemophilia C, Sickle cell anemia, Cystic fibrosis. \textbf{Holandric genes:} Genes present on the Y chromosome, passed only from father to son.

Answer 1

The Correct Option is D

Step 1: Analyze Statement I
Statement I says: "Haemophilia is an X-linked disorder due to dominant genes."
Haemophilia (specifically Hemophilia A and B) is an X-linked recessive disorder. This means the gene responsible is located on the X chromosome, and the disorder manifests primarily in males (who have only one X chromosome) or in females who are homozygous for the recessive allele. It is not caused by dominant genes. Therefore, Statement I is Incorrect. Step 2: Analyze Statement II
Statement II says: "Inheritance of colour blindness follows the cris-cross pattern."
Colour blindness (specifically red-green color blindness) is also an X-linked recessive disorder. The "cris-cross" pattern of inheritance refers to the transmission of a trait from a father to his daughter (who is usually a carrier) and then from the daughter to her son. This pattern is characteristic of X-linked recessive traits. Therefore, Statement II is Correct. Step 3: Analyze Statement III
Statement III says: "Haemophilia A and Haemophilia C are X-linked disorders."
Haemophilia A (Factor VIII deficiency) and Haemophilia B (Factor IX deficiency, also known as Christmas disease) are both X-linked recessive disorders.
Haemophilia C (Factor XI deficiency, also known as Rosenthal syndrome) is inherited in an autosomal recessive pattern, not X-linked. Therefore, Statement III is Incorrect. Step 4: Analyze Statement IV
Statement IV says: "Y-linked genes are called holandric genes." Genes located on the Y chromosome are transmitted directly from father to son. These genes are indeed called holandric genes. Therefore, Statement IV is Correct. Step 5: Identify the incorrect statements
Based on the analysis:
Statement I is Incorrect.
Statement II is Correct.
Statement III is Incorrect.
Statement IV is Correct.
The question asks to pick up the incorrect statements. The incorrect statements are I and III. Step 6: Choose the correct option
The option that contains both I and III is (4).