GATE 2021 BT – Question 43
Neurospora crosses yield: wild-type female × wild-type male → all wild-type; wild-type female × poky male → all wild-type; poky female × wild-type male → all poky; poky female × poky male → all poky. What explains poky inheritance?
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Correct answer: (C) Mitochondrial inheritance
Explanation
Look at the reciprocal crosses (the female parent is written first):
- wild-type ♀ × poky ♂ → all wild-type.
- poky ♀ × wild-type ♂ → all poky.
The offspring always take the phenotype of the **mother**, whichever way the cross goes. This is **maternal (uniparental) inheritance**, which means the gene is carried in the cytoplasm and not in the nucleus.
- **Mendelian inheritance:** would give the same result in reciprocal crosses. ✗
- **X-linked inheritance:** Neurospora does not have sex chromosomes of this type and the pattern would differ. ✗
- **Episomal inheritance:** applies to plasmid-like elements, not to this system. ✗
- **Mitochondrial inheritance:** the mitochondria come only from the maternal parent (the large female gamete), and the *poky* mutation is in mitochondrial DNA. ✓
Answer **C**.