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1

1) When an F1 hybrid does not resemble either pure breeding parents
2) Intermediate phenotype where both parental alleles contribute to the phenotype
3) 1:2:1 phenotypic ratio exactly reflects the genotype can ratio
4) recessive may not be expressing a viable protein (snap dragons)

Incomplete dominance

2

1) Both traits show up equally in the heterozygotes phenotype in the F1 cross (spotted dotted lentils) 2)1:2:1 in the F2 generation 3) blood group alleles (a and b sugars)

Codominant

3

Novel phenotype determined by 2 or more genes, or from interactions between genes and the environment (green lentils) 9:3:3:1

Multifactorial

4

A given gene may have more than two alleles.
Sugar adding enzyme in blood

Multiple alleles

5

Alleles are listed in order from most to least dominant

Dominance series

6

Chance alterations of the genetic material that are spontaneous in nature

Mutations

7

Percentage of the total number of gene copies

Allele frequency

8

The most common alleles of each gene In a population, or if present, at a frequency of greater than 1%, often designated +

Wild type

9

Rare allele

Mutant allele

10

A gene with only one common wild type allele,
Agouti,
More than 99% frequency

Monomorphic

11

Some genes have more than one common allele,
ABO blood type system

Polymorphic

12

High frequency alleles of a polymorphic gene,
ABO blood type system

Common variants

13

When a single gene determines a # of distinct and seemingly unrelated characteristics,

Mutations can influence multiple biochemical processes

Plieotropy

14

An allele that negatively affects the survival of a Homozygote, 1:2 phenotypic ratio indicates a missing genotype

Recessive lethal alleles

15

Extension: Incomplete dominance or codominance,
On crossing F1, Phenotypes are 1:2:1,
Unlike either Homozygote

Extension to complete dominance

16

Extension: multiple alleles
Multiplicity of Phenotypes
Series of 3:1 ratios

Extension to two alleles

17

Extension: recessive lethal alleles
2:1 instead of 3:1
Heterozygotes survive but may have visible Phenotypes

Extension to all alleles are equally viable

18

Extension: Plieotropy,
One gene affects Several traits, affected several ways depending on dominance relationships, Different ratios

Extension to one gene determines one trait

19

Two genes working in tandem To produce purple sweet pea flowers, a dominant allele of each gene (producing white flowers) must be present (in opposite parents) to produce that color
9:7 in the F2; A-B- is the only purple phenotype

Complementary gene action

20

A gene interaction in which the effects of an allele at one gene hide the effects of alleles at another gene. Can be either dominant or recessive.

Epistasis

21

Homozygous for a recessive allele of the second gene is required to hide the effects of another gene to cause a masking phenomenon

9:3:4 in Chocolate labs

Recessive Epistasis

22

Dark color in dog coats

Eumelanin

23

Light color of dog coats

Pheomelanin

24

Epistasis when the dominant allele of one gene hides the effects of another gene

Chickens

Dominant Epistasis

25

15:1
Specify nearly identical proteins that perform the same function

Redundant gene action

26

One dominant allele of each of 2 genes is Necessary to produce phenotype
9:7
Sweet pea flowers

Complementarity

27

Homozygous recessive of one gene masks both alleles of another
9:3:4
Labrador retriever coat color

Recessive Epistasis

28

Dominant allele of one gene masks the effects of both alleles of another gene 12:3:1
Summer squash color

Dominant Epistasis 1

29

Dominant allele of one gene hides effects of dominant allele of other gene
13:3
Chicken feathers

Dominant Epistasis 2

30

Only one dominant allele of either of 2 genes is necessary to produce a phenotype
15:1
Maize leaves

Redundancy