Exploring Mendelian Genetics 11-3 Independent Assortment Inheritance Patterns Beyond Simple Dominance

Quick Review  Allele: each letter (R or r) Dominant masks Recessive (Rr or rr)  Law of Dominance?  Homozygous RR/rr  Heterozygous Rr

Law of Independent Assortment  States that genes for different traits can segregate independently during meiosis  Gives many more genetic variations  MEANING: If a pea plant is yellow and wrinkled, both sets of alleles will separate independently (they work alone!)  An offspring can receive any combination of r’s and y’s

Dihybrid Crosses Used For Proof (pg 270/271)

Incomplete Dominance  Dominant and Recessive Blend in a heterozygous genotype  Ex: Flower Color  Red (RR) Flower X White (rr) Flower =PINK (Rr)  Can you think of other examples?

Co dominance  No recessive, Both traits expressed  Ex:coat color  Heterozygous will both be capital letters because both dominant!

RR=Black, WW=White, RW=Black and White Bunny

Other Ways To Show Genotypes  Use 2 different letters (all caps)  Ex: BW=black and white bunny  Use apostrophes to show the other allele  Ex: RR = red R’R’ = white RR’=Roan  (Roan= both)  Found in cows, horses, dogs, etc

Examples of Roan Animals (co-dominant coat color)

Multiple Alleles  Genes with 3 or more alleles  Ex: Blood Typing  3 alleles = I A, I B, i  Give 4 possible phenotypes: A (I A I A, I A i) B (I B I B, I B i) AB (I A I B ) O (ii)

Here’s How… AA= A Ai = A BB = B Bi = B AB= AB ii = O

Polygenic Trait  Several Genes Influence a Trait  Ex: Skin, Weight, Eye Color, Height  Most genes scattered along the same chromosome  What causes so many variations?

Traits Influenced by Environment  Phenotypes can change based on environment  Ex: Hydrangea Color  Fur in mammals (color and thickness)  Height and weight in humans based nutrition