One of the parents of a cross has a mutation in its mitochondria. In that cross, that parent is taken as a male. During segregation of $F_2$ progenies that mutation is found in -
A
None of the progenies
B
All the progenies
C
50% of the progenies
D
$\dfrac{1}{3}$ of the progenies
The answer is A.
Solution
Mitochondrial DNA is inherited through the cytoplasm. During fertilisation, the egg contributes almost all of the cytoplasm (and mitochondria) to the zygote. The sperm contributes mainly its nucleus; its few mitochondria are lost or destroyed. So mitochondrial traits show maternal (uniparental) inheritance: they are passed only through the female parent. Here the parent with the mitochondrial mutation is the male, so its mitochondria are not transmitted to the $F_1$, and therefore not to the $F_2$ either. So the mutation is found in none of the progenies.
ConceptMitochondrial genes are maternally inherited
Principles of Inheritance and Variation in past papers
198 questions from this chapter have appeared across 27 exam years.
