Question

Extra-chromosomal inheritance is often called maternal inheritance because

• A. Genes are inherited from both parents equally
• B. Cytoplasm of the zygote is mainly contributed by the mother
• C. Organellar genes show dominance
• D. Only females show the trait

Hint:

Maternal inheritance is due to inheritance of \[ \boxed{ \text{mitochondrial DNA and chloroplast DNA} } \] through the egg cytoplasm.

Answer 1

The Correct Option is B

Step 1: Recall extra-chromosomal inheritance. Extra-chromosomal inheritance involves genes present in
• Mitochondria,
• Chloroplasts. These organelles are transmitted through the cytoplasm.

Step 2: Identify the reason for maternal inheritance. During fertilization, the egg contributes almost all of the cytoplasm to the zygote, whereas the sperm contributes mainly the nucleus. Hence, \[ \boxed{ \text{Organellar DNA is usually inherited from the mother.} } \] Therefore, \[ \boxed{ \text{Cytoplasm of the zygote is mainly contributed by the mother.} } \] Thus, \[ \boxed{(B)} \] is the correct answer.