Codominant. Both alleles affect the phenotype in separate, distinguishable ways.

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Lenard Casey
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1 Codominant Both alleles affect the phenotype in separate, distinguishable ways.

2 Codominance Alleles for a gene are both dominant Both alleles are expressed when present Examples: Roan cow or horse

3 Codominance: Horses B = brown W = white B B W W X = BW BW BW BW Genotype: 100% BW Phenotype:?

4 Codominant Incomplete Dominance Both alleles affect the phenotype in separate, distinguishable ways. Phenotype is a blend of both alleles when heterozygous

5 Incomplete Dominance Dominant allele of a gene does NOT complete mask the recessive allele Phenotype is a blend of both dominant and recessive phenotypes Example: Snapdragons

6 Incomplete Dominance: Snapdragons R = red r = white X = Rr Rr Rr Rr Genotype: 100% Rr Phenotype:? 100% PINK

7 Incomplete Dominance: Snapdragons Parental (P) Generation F 1 Generation F 2 Generation

8 Codominant Incomplete Dominance Multiple Alleles Both alleles affect the phenotype in separate, distinguishable ways. Phenotype is a blend of both alleles when heterozygous More than two alleles exist for one gene

9 Multiple Alleles More than 2 alleles exist for one gene. Example: Blood type (also codominant) Type A = AA or AO Type B = BB or BO Type AB = AB Type O = OO

10 Type A Blood Type B Blood Type A Antigen Type B Antigen Codominant with B Allele Codominant with A Allele Possible genotypes Possible genotypes AA or AO BB or BO Type AB Blood Type O Blood Neither A nor B Antigens Both A and B Antigens Recessive to both A and B A and B are codominant, Alleles so both are expressed Only possible genotype Only possible genotype OO AB

11 Multiple Alleles: Blood Types

12 Multiple Alleles: Blood Types A B AB AA or AO BB or BO AB O OO

13 Multiple Alleles: Blood Types Question: If a boy has Type O blood and his sister has Type AB blood Answer: What are the genotypes and phenotypes of their parents? Boy Type O & Girl Type AB A O B AB BO Parents must be: AO x BO O AO OO

B - 1.5% B + 8.5% A - 6.3% O + 37.4% A + 35.7% O - 6.6% AB + 3.4% AB - 0.6% Blood Type Rh Factor How many have it?

14 B - 1.5% B + 8.5% A - 6.3% O % A % O - 6.6% AB + 3.4% AB - 0.6% Blood Type Rh Factor How many have it? O Positive 1 in 3 Negative 1 in 15 A Positive 1 in 3 Negative 1 in 16 B Positive 1 in 12 Negative 1 in 67 AB Positive 1 in 29 Negative 1 in 167

Blood donation New disposable, sterile needles are used for each donor. Each donor is given a mini-physical to be sure that it is safe for them to give blood.

15 Blood donation New disposable, sterile needles are used for each donor. Each donor is given a mini-physical to be sure that it is safe for them to give blood. The actual blood donation usually takes less than 15 minutes. All blood is tested for HIV, hepatitis B & C, syphilis, and other infections before it is used. Information given during the donation process is confidential. Blood needs & supply More than 38,000 blood donations are needed every day. A single car accident victim can require as many as 100 pints of blood. 16 million blood donations are collected per year from 9.5 million people.

Codominant Incomplete Dominance Multiple Alleles Polygenic Inheritance Both alleles affect the phenotype in separate, distinguishable ways.

16 Codominant Incomplete Dominance Multiple Alleles Polygenic Inheritance Both alleles affect the phenotype in separate, distinguishable ways. Phenotype is a blend of both alleles when heterozygous More than two alleles exist for one gene An additive effect of two or more genes on a single phenotypic character

17 Polygenic Traits Characteristics that are controlled by more than a single gene Often a trait that has a wide range of phenotypes» Examples:» Height» Eye color» Skin color» Hair color

18 Polygenic Traits Are there more than just two or three heights for humans? The more possibilities, the more genes that control the trait! Can you think of any other traits that have a large number of variations?

19 Polygenic Traits: Skin color Three genes code for melanin Dominant alleles (A, B, and C) make pigment Recessive alleles (a, b, c) do not make pigment The more dominant alleles, the darker the skin

20 Polygenic Traits: Skin color

21 Codominant Incomplete Dominance Multiple Alleles Polygenic Inheritance Pleiotropy Both alleles affect the phenotype in separate, distinguishable ways. Phenotype is a blend of both alleles when heterozygous More than two alleles exist for one gene An additive effect of two or more genes on a single phenotypic character One gene has multiple phenotypic effects

22 Pleiotropy One gene has multiple phenotypic effects Example: Sickle-Cell Anemia

Exploring Mendelian Genetics 11-3

Exploring Mendelian Genetics 11- GENES are more complicated than Mendel thought Some traits have MORE than 2 allele choices = MULTIPLE ALLELE TRAIT http://www.eslkidstuff.com/images/tallshort.gif EX: blood