University:
Swansea University
Course:
PM-149 | Genetics, Genomics & Evolution
Academic year:

2023
Views:

364

Pages:

4
Author:

Amal J.

Quantitative Genetics Monohybrid Cross AA x aa ↓ Aa ↓ Aa x Aa AA Aa Aa aa 1 : 2 : 1 Genotypic 3 : 1 Phenotypic Dihybrid ratio (3:1)² = 9 : 3 : 3 : 1 Trihybrid (3:1)³ = 27 : 9 : 9 : 9 : 3 : 3 : 3 : 1 Tetrahybrid (3:1)⁴ = 81 : 27 : 27 : 27 : 27 : 9 : 9 : 9 : 9 : 9 : 9 : 3 : 3 : 3 : 3 : 1 (P+q)² = p² + 2pq + q² → for diploids (P+q)³ → for triploids P + q = 1 Blood group ABO (P₁+q₁+r₁)² = p₁² + 2p₁q₁ + q₁² + 2p₁r₁ + 2q₁r₁ + r₁² A B O A B AB AO BO Skin color, height - Quantitative/Polygenic ↓ Additive Effect AA aa F₁ Aa F₁ filial generate average weight (8+2)/2 = 5g AA 8g Aa 5g aa 2g 1 : 2 : 1 → phenotypic & genotypic ratio No. of individuals = 4ⁿ No. of phenotypes = 4√ + 2ⁿ 2⁰+1 Normal distribution curve Purple × white A⁺A⁺B⁺B⁺ × A⁻A⁻B⁻B⁻ ↓ Red A⁺A⁻B⁺B⁻ (AaBb also similar representation) Aax Aa Bb x Bb AA 2Aa aa BB 2Bb bb ½ 2/4 ¼ ¼ 2/4 ¼ ¼ AA × BB ¾ Bb × ¾ Aa× Bb ¼ AA × BB ¼ AaBB ¼ AABb ¼ AaBb ¼ aabb No. of phenotypes = 2ⁿ+1 = 5 No. of phenotypes = 2×2×1 = 5 Polygenic trait Polygenic trait Vaults of maize 48 & 72 inches, crossed F₁ uniform = 60 inches 500 F₂ plants shortest 48 inch (2) tallest 72 inch (2) Probable no. of polygenes Alleles Mono = 12:1 Di = 14:6:4:1 Tri = 6:15:6:1 Tetra = 18:28:56:70:98:128:8:1

Quantitative Genetics: Monohybrid Cross and Alleles

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