non-Mendelian ratios

mendels laws

1. Principle of segregation

2. principal of independent assortment

conditions true to mendel

1. all traits were unlinked

   1. independent assortment

   2. genes on diff chromosomes

2. every gene has 2 alleles

   1. unique phenotypes

   2. all had complete dominance

3. genotype determines phenotype

alleles on a single locus

1. diff types of dominance

2. multiple alleles

3. lethal alleles

multiple loci and environment

1. incomplete penetrance

2. variable expressivity

dominance relationships (diff types of dominance)

complete dominance

incomplete/partial dominance

codominance

complete dominance

childs trait always resembles parents trait → dominant masks recessive

incomplete/partial dominance

heterozygote is intermediate of homozygote (blended inheritance)

• red x white → pink

• R1R1 x R2R2 → R1R2

• phenotype ratio = genotype ratio = 1:2:1

codominance

heterozygous shows both homozygous phenotypes

• blood type: AA x BB → AB

  • iAiA x iBiB → iAiB

• A/B code for different proteins on cell surface

• i is nonfunctional and doesnt code for any proteins → ii = type O

• iA = iB iA>i iB>i

multiple alleles

when more than 2 alleles for each trait are present in a population they could form a dominance series

dominance series

properties of alleles in relation to eachother

• A>a>B>b>C>c

lethal alleles

allele combinations that lead to death → can be dominant or recessive

penetrance

proportion of individuals with a genotype that shows the expected phenotype

variable expressivity

phenotypes have a range from the same genotype → variation in severity of a trait