Patterns of Inheritance Beyond Dominant and Recessive

What we have learned up to this point is called complete dominance.

What we have learned up to this point is called complete dominance. With complete dominance, the heterozygote shows the dominant phenotype.

What we have learned up to this point is called complete dominance. With complete dominance, the heterozygote shows the dominant phenotype. For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes?

What we have learned up to this point is called complete dominance. With complete dominance, the heterozygote shows the dominant phenotype. For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes? BB: Bb: bb:

What we have learned up to this point is called complete dominance. With complete dominance, the heterozygote shows the dominant phenotype. For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes? BB: Brown Bb: bb:

What we have learned up to this point is called complete dominance. With complete dominance, the heterozygote shows the dominant phenotype. For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes? BB: Brown Bb: Brown bb:

What we have learned up to this point is called complete dominance. With complete dominance, the heterozygote shows the dominant phenotype. For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes? BB: Brown Bb: Brown bb: White

This isn’t always the case This isn’t always the case. These new types of inheritance are all EXCEPTIONS to complete dominance.

Incomplete Dominance The heterozygote displays an intermediate phenotype that is a blending of the dominant and recessive phenotypes.

Incomplete Dominance Example: Snap dragons RR = rr = Rr =

Incomplete Dominance Example: Snap dragons RR = Red flowers rr = Rr =

Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr =

Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers

Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers Genotypic Ratio: Phenotypic Ratio:

Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: Phenotypic Ratio:

Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: Phenotypic Ratio: R r

RR Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: Phenotypic Ratio: RR R r

RR Rr Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: Phenotypic Ratio: RR Rr R r

RR Rr Rr Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: Phenotypic Ratio: RR Rr R Rr r

RR Rr Rr rr Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: Phenotypic Ratio: RR Rr R Rr rr r

RR Rr Rr rr Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: 1:2:1 Phenotypic Ratio: RR Rr R Rr rr r

RR Rr Rr rr Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: 1:2:1 Homozygous Dom.: Heterozygous: Homozygous Rec. Phenotypic Ratio: RR Rr R Rr rr r

RR Rr Rr rr Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: 1:2:1 Homozygous Dom.: Heterozygous: Homozygous Rec. Phenotypic Ratio: RR Rr R Rr rr r

RR Rr Rr rr Incomplete Dominance Example: Snap dragons RR = Red flowers rr = White flowers Rr = Pink flowers R r Genotypic Ratio: 1:2:1 Homozygous Dom.: Heterozygous: Homozygous Rec. Phenotypic Ratio: Red: Pink: White RR Rr R Rr rr r

Codominance The heterozygote displays the phenotype of both of the alleles it possesses Both alleles act as dominant alleles and show up independently (such as with spots) Remember co- means together, so in codominance the heterozygote shows both traits together.

Codominance Example: Roan Coat Color in Cows RR = WW = RW =

Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = RW =

Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW =

Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat

Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat All capital letters!

Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat Genotypic Ratio: Phenotypic Ratio: All capital letters!

Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat Genotypic Ratio: Phenotypic Ratio: R W All capital letters!

Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat Genotypic Ratio: Phenotypic Ratio: R W R All capital letters! W

RR RW RW WW Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat Genotypic Ratio: Phenotypic Ratio: R W RR RW R All capital letters! RW WW W

RR RW RW WW Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat Genotypic Ratio: 1:2:1 Phenotypic Ratio: R W RR RW R All capital letters! RW WW W

RR RW RW WW Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat Genotypic Ratio: 1:2:1 RR:RW:WW Phenotypic Ratio: R W RR RW R All capital letters! RW WW W

RR RW RW WW Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan coat Genotypic Ratio: 1:2:1 RR:RW:WW Phenotypic Ratio: R W RR RW R All capital letters! RW WW W

RR RW RW WW Codominance Example: Roan Coat Color in Cows RR = Brown coat WW = White coat RW = Roan Genotypic Ratio: 1:2:1 RR:RW:WW Phenotypic Ratio: Brown: Roan: White R W RR RW R All capital letters! RW WW W

Multiple Alleles

Multiple Alleles A gene that has three or more genes

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): , , , and

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): A , , , and

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): A , B , , and

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): A , B , AB , and

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): A , B , AB , and O

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): A , B , AB , and O Blood type is controlled by three alleles: , , or

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): A , B , AB , and O Blood type is controlled by three alleles: A , , or

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): A , B , AB , and O Blood type is controlled by three alleles: A , B , or

Multiple Alleles A gene that has three or more genes Example: Human ABO Blood Groups In humans, there are four blood types (phenotypes): A , B , AB , and O Blood type is controlled by three alleles: A , B , or O

Multiple Alleles These alleles code for types of carbohydrates that are on the surface of the red blood cells. Allele A codes for A type carbohydrates. Allele B codes for B type carbohydrates. Allele O codes for no carbohydrates. The O allele is recessive. Two O alleles must be present for the person to have O type blood.

Multiple Alleles The A and B alleles are codominant. If a person receives an A allele and a B allele, their blood type is AB. The AB blood cells have both A and B type carbohydrates.

Multiple Alleles Phenotype Genotypes A B AB O

Multiple Alleles Phenotype Genotypes A AA B AB O

Multiple Alleles Phenotype Genotypes A AA, AO B AB O

Multiple Alleles Phenotype Genotypes A AA, AO B BB AB O

Multiple Alleles Phenotype Genotypes A AA, AO B BB, BO AB O

Multiple Alleles Phenotype Genotypes A AA, AO B BB, BO AB O

Multiple Alleles Phenotype Genotypes A AA, AO B BB, BO AB O OO

Multiple Alleles AB x AB Genotypic Ratio: Phenotypic Ratio:

Multiple Alleles AB x AB A B Genotypic Ratio: Phenotypic Ratio: A B

Multiple Alleles AB x AB A B Genotypic Ratio: Phenotypic Ratio: AA AB BB B

Multiple Alleles AB x AB A B Genotypic Ratio: 1:2:1 AA:AB:BB Phenotypic Ratio: AA AB A AB BB B

Multiple Alleles AB x AB A B Genotypic Ratio: 1:2:1 AA:AB:BB Phenotypic Ratio: A:AB:B AA AB A AB BB B

Multiple Alleles AO x BO Genotypic Ratio: Phenotypic Ratio:

Multiple Alleles AO x BO A O Genotypic Ratio: Phenotypic Ratio: B O

Multiple Alleles AO x BO A O Genotypic Ratio: Phenotypic Ratio: AB BO OO O

Multiple Alleles AO x BO A O Genotypic Ratio: 1:1:1:1 AB:BO:AO:OO Phenotypic Ratio: AB BO B AO OO O

Multiple Alleles AO x BO A O Genotypic Ratio: 1:1:1:1 AB:BO:AO:OO Phenotypic Ratio: AB:B:A:O AB BO B AO OO O

Polygenic Traits Traits controlled by 2 or more genes Usually see a lot of possible phenotypes Examples: Height, eye color

Plietropy A single gene affects more than one trait Sick cell anemia Affects the shape of the blood cells Causes heart damage Causes brain damage Weakness

Epistasis One gene impacts the expression of another gene Example: Albinism The recessive genotype for albinism (aa) masks the genes for eye and hair color. As a result, albinos have white hair and pink eyes.

Environmental Effects The environment can influence the phenotype of an organism Example: Arctic fox In the summer, the fox is brown because its DNA codes for brown pigments. In the winter, the enzyme does not function because it’s too cold. The fox becomes white.

Summer Winter

Sex-Linked Genes

Sex-Linked Genes Genes located on the X-chromosome

Sex-Linked Genes Genes located on the X-chromosome Remember organisms have (chromosomes that do not determine an organism’s sex) and (chromosomes that DO determine an organism’s sex)

Sex-Linked Genes Genes located on the X-chromosome Remember organisms have autosomes (chromosomes that do not determine an organism’s sex) and (chromosomes that DO determine an organism’s sex)

Sex-Linked Genes Genes located on the X-chromosome Remember organisms have autosomes (chromosomes that do not determine an organism’s sex) and sex chromosomes (chromosomes that DO determine an organism’s sex)

Sex-Linked Genes Females have as their sex chromosomes and males have

Sex-Linked Genes Females have XX as their sex chromosomes and males have

Sex-Linked Genes Females have XX as their sex chromosomes and males have XY

Sex-Linked Genes Females have XX as their sex chromosomes and males have XY Because males only have 1 X chromosome, they only need one recessive allele to show the recessive phenotype.

Sex-Linked Genes Females have XX as their sex chromosomes and males have XY Because males only have 1 X chromosome, they only need one recessive allele to show the recessive phenotype. A female who has a recessive allele on only one X chromosome will not display the recessive phenotype.

Sex-Linked Genes Example: Red-Green Color Blindness Normal vision, XN, is dominant to colorblindness, Xn. Phenotypic Ratio Genotypic Ratio

Sex-Linked Genes XN Xn x XNY Example: Red-Green Color Blindness Normal vision, XN, is dominant to colorblindness, Xn. XN Xn x XNY Phenotypic Ratio Genotypic Ratio

Sex-Linked Genes XN Xn x XNY XN Xn Example: Red-Green Color Blindness Normal vision, XN, is dominant to colorblindness, Xn. XN Xn x XNY XN Xn Phenotypic Ratio Genotypic Ratio

Sex-Linked Genes XN Xn x XNY XN Xn XN Y Example: Red-Green Color Blindness Normal vision, XN, is dominant to colorblindness, Xn. XN Xn x XNY XN Xn Phenotypic Ratio Genotypic Ratio XN Y

Sex-Linked Genes XN Xn x XNY XN Xn XN XN Xn XN XN Y Xn Y XN Y Example: Red-Green Color Blindness Normal vision, XN, is dominant to colorblindness, Xn. XN Xn x XNY XN Xn Phenotypic Ratio Genotypic Ratio XN XN Xn XN XN Y Xn Y XN Y

Sex-Linked Genes XN Xn x XNY XN Xn XN XN Xn XN XN Y Xn Y XN Y Example: Red-Green Color Blindness Normal vision, XN, is dominant to colorblindness, Xn. XN Xn x XNY XN Xn Phenotypic Ratio 1:1:1:1 Colorblind female: Normal female: Colorblind male: Normal male Genotypic Ratio XN XN Xn XN XN Y Xn Y XN Y

Sex-Linked Genes XN Xn x XNY XN Xn XN XN Xn XN XN Y Xn Y XN Y Example: Red-Green Color Blindness Normal vision, XN, is dominant to colorblindness, Xn. XN Xn x XNY XN Xn Phenotypic Ratio 1:1:1:1 Colorblind female: Normal female: Colorblind male: Normal male Genotypic Ratio XNXN:XNXn:XNY:XnY XN XN Xn XN XN Y Xn Y XN Y

Pedigree Family tree that traces the inheritance of traits through many generations Symbols: Normal Affected Male Female

I II Pedigree Mating Generations I1 II3 Names are determined by giving the generation number and the number they are in the row, counting left to right. Children from mating

Pedigree Carrier-

Pedigree Carrier- an individual who carries a recessive gene but is unaffected by the gene

Pedigree Carrier- an individual who carries a recessive gene but is unaffected by the gene Pedigree problems have you determine the pattern of inheritance of a gene (dominant or recessive, autosomal or sex-linked) within a family.

Pedigree Carrier- an individual who carries a recessive gene but is unaffected by the gene Pedigree problems have you determine the pattern of inheritance of a gene (dominant or recessive, autosomal or sex-linked) within a family. To do these problems, there are three steps you should follow.

1. Determining if a trait is dominant or recessive.

1. Determining if a trait is dominant or recessive. Common patterns of dominant traits:

1. Determining if a trait is dominant or recessive. Common patterns of dominant traits: Vertical patterns of inheritance meaning that there is an infected individual in each generation.

1. Determining if a trait is dominant or recessive. Common patterns of dominant traits: Vertical patterns of inheritance meaning that there is an infected individual in each generation.

1. Determining if a trait is dominant or recessive.

1. Determining if a trait is dominant or recessive. Common patterns of recessive traits:

1. Determining if a trait is dominant or recessive. Common patterns of recessive traits: Horizontal patterns of inheritance meaning that there usually are multiple affected individuals within an generation

1. Determining if a trait is dominant or recessive. Common patterns of recessive traits: Horizontal patterns of inheritance meaning that there usually are multiple affected individuals within an generation Often skips generations so the trait may appear after several generations of unaffected individuals

1. Determining if a trait is dominant or recessive. Common patterns of recessive traits: Horizontal patterns of inheritance meaning that there usually are multiple affected individuals within an generation Often skips generations so the trait may appear after several generations of unaffected individuals

2. Determining if a trait is autosomal or sex-linked

2. Determining if a trait is autosomal or sex-linked Common characteristics of a sex-linked recessive gene

2. Determining if a trait is autosomal or sex-linked Common characteristics of a sex-linked recessive gene Occurs more often in males than females

2. Determining if a trait is autosomal or sex-linked Common characteristics of a sex-linked recessive gene Occurs more often in males than females Often skips generations through female carriers (heterozygotes). All of the daughters of affected males are carriers.

2. Determining if a trait is autosomal or sex-linked Common characteristics of a sex-linked recessive gene Occurs more often in males than females Often skips generations through female carriers (heterozygotes). All of the daughters of affected males are carriers.

3. Always fill in the genotypes for individuals in the pedigree.

3. Always fill in the genotypes for individuals in the pedigree. Doing this will help you double check that you determined the correct pattern of inheritance.

Patterns in Pedigrees Inheritance Affected Generations Affected Males and Females Autosomal Dominant Autosomal Recessive Sex-Linked Recessive

Patterns in Pedigrees Inheritance Affected Generations Affected Males and Females Autosomal Dominant Trait appears in every generation (vertical pattern) Autosomal Recessive Sex-Linked Recessive

Patterns in Pedigrees Inheritance Affected Generations Affected Males and Females Autosomal Dominant Trait appears in every generation (vertical pattern) Equally likely to affect male and female Autosomal Recessive Sex-Linked Recessive

Patterns in Pedigrees Inheritance Affected Generations Affected Males and Females Autosomal Dominant Trait appears in every generation (vertical pattern) Equally likely to affect male and female Autosomal Recessive May skip a generation; may have multiple affected in a single generation (horizontal pattern) Sex-Linked Recessive

Patterns in Pedigrees Inheritance Affected Generations Affected Males and Females Autosomal Dominant Trait appears in every generation (vertical pattern) Equally likely to affect male and female Autosomal Recessive May skip a generation; may have multiple affected in a single generation (horizontal pattern) Sex-Linked Recessive

Patterns in Pedigrees Inheritance Affected Generations Affected Males and Females Autosomal Dominant Trait appears in every generation (vertical pattern) Equally likely to affect male and female Autosomal Recessive May skip a generation; may have multiple affected in a single generation (horizontal pattern) Sex-Linked Recessive May skip a generation; all daughters of affected males are carriers

Patterns in Pedigrees Inheritance Affected Generations Affected Males and Females Autosomal Dominant Trait appears in every generation (vertical pattern) Equally likely to affect male and female Autosomal Recessive May skip a generation; may have multiple affected in a single generation (horizontal pattern) Sex-Linked Recessive May skip a generation; all daughters of affected males are carriers More often male than female