Download 11.2 Complex Patterns

Complex Patters of
Inheritance
11-2
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 < RrYy>, 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
Sex-Linked Traits
 Traits controlled by genes on the X
chromosome. (X-linked traits)
 Ex: Red-green color blindness and
Hemophilia
 It is a recessive X-linked trait.
Sex Determination
 Sex chromosomes
determine an
individual’s gender.
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 = IA, IB, i
 Give 4 possible phenotypes:




A (IAIA, IAi)
B (IBIB, IBi)
AB (IAIB)
O (ii)
Here’s How…
AA= A
Ai = A
BB = B
Bi = B
AB= AB
ii = O
Epistasis
 One allele hides the effect of another allele.
 Ex: Labrador’s coat color is controlled by 2 sets of
alleles.
 The dominant allele “E” determines whether the fur will
have dark pigment. Eebb, Eebb, EeBe
 Black and Chocolate vs White and Yellow.
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