Dominant Epistasis 12:3:1 Ratio | Gene Interaction NEET Biology Class 12 | Neela Bakore Tutorials

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Dominant Epistasis — one dominant allele masks both alleles of another gene, giving 12:3:1 ratio!

📌 Topics Covered:
• What is Dominant Epistasis?
• 12:3:1 ratio — how it arises
• Classic example: summer squash (Cucurbita pepo) fruit colour
• Step-by-step cross solution
• Dominant (12:3:1) vs Recessive (9:3:4) Epistasis
• NEET MCQ tricks
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Transcript with Timestamp
0:00 Introduction — Dominant Epistasis
0:14 Epistasis = one gene suppresses another at a different locus
0:55 Epistatic gene (suppressor) vs Hypostatic gene (suppressed)
1:59 Dominant epistasis — suppression in DOMINANT form of epistatic gene
2:21 Recessive epistasis — suppression in RECESSIVE form
2:40 Example: Cucurbita pepo (Summer Squash) — 3 fruit colours
3:24 W (epistatic, dominant) → white — suppresses Y. wwY_ → yellow. wwyy → green
4:03 Cross: white (WWyy) × green (wwYY)
5:04 F1: all WwYy = all WHITE (W dominant — suppresses Y)
5:43 F2 selfing of F1 (WwYy × WwYy) — 4 types of gametes
6:37 F2: wherever W is dominant → WHITE (12 plants)
7:06 F2: no W dominant + Y dominant → YELLOW (3 plants)
8:37 F2: W recessive + Y recessive → GREEN (1 plant)
9:33 ⚠️ Ratio = 12:3:1 — dominant epistasis modified dihybrid ratio
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