Patterns of Inheritance Incomplete Dominance Codominance Multiple Alleles

Patterns of Inheritance Incomplete Dominance, Codominance, Multiple Alleles, Genetic Disorders, & Sex-Linked Genes

I) Incomplete Dominance A) Snapdragon Flowers

I) Incomplete Dominance B)Individual has a trait that appears to be an intermediate form of the traits displayed by each parent

I) Incomplete Dominance • R = Red • W = White • RW=Pink • R = W • Pink X Pink Flower Cross

R W R RR RW • Genotypes –RR: 1 –RW: 2 –WW: 1 • Phenotypes W RW WW –Red: 1 –Pink: 2 –White: 1

II) Codominance A) Roan Horse Color

II) Codominance B)Both genes of the heterozygote are fully expressed; thus, you see both colors

II) Codominance • R = Red • R = W • W = White • RW = Roan • Roan X Roan (Red/White) Horse Cross

R W R RR RW • Genotypes –RR: 1 –RW: 2 –WW: 1 • Phenotypes W RW WW –Red: 1 –Roan: 2 –White: 1

III) Multiple Alleles A) Human ABO Blood Types

III) Multiple Alleles B)Some traits are controlled by genes that have more than two alleles

III) Multiple Alleles • i. A > i B • i >i • i. A = i B • i. A or i. Ai = A-Blood B B B • i i or i i = B-Blood • ii = O-Blood A B • i i = AB-Blood • Cross a heterozygous Ablood man with a heterozygous B-blood woman

B i i A i i ii • Genotypes – i. A i. B : 1 – i. Bi: 1 – i. Ai: 1 – ii: 1 • Phenotypes – AB Blood: 1 – A Blood: 1 – O Blood: 1

IV) Sex-Linked Inheritance A) Colorblindness & Hemophilia

IV) Sex-Linked Inheritance B) Colorblindness: genetic disease characterized by the inability to see certain colors (there are different types of colorblindness) 1) Mutation is on the X-chromosome C) Hemophilia: genetic disease characterized by the blood’s inability to clot 1) Mutation is on the X-chromosome

IV) Sex-Linked Inheritance • X > XC • XX = Normal ♀ C • Y plays • XX = Carrier ♀ C C no part • X X = Colorblind ♀ • XY = Normal ♂ C • X Y = Colorblind ♂ • Cross a carrier ♀ with a normal ♂

X C X X XX C XX Y XY C X Y • Genotypes – XX: 1 – XXC: 1 – XY: 1 – XCY: 1 • Phenotypes – Normal ♀: 1 – Carrier ♀: 1 – Normal ♂: 1 – Colorblind ♂: 1

V) Polygenic Traits A) Interaction of several genes

VII) Polygenic Traits B) Traits controlled by two or more genes C) Often show a wide range of phenotypes

V) Polygenic Traits

VI) Pedigrees

VI) Genetic Disorders A) Sickle-Cell Anemia & Cystic Fibrosis

VI) Genetic Disorders A) Sickle-Cell Anemia: 1) Recessive disorder affecting hemoglobin, on chromosome #11 2) Gives red blood cells a deformed appearance 3) Heterozygous carriers are more immune to malaria; Recessives are immune to malaria 4) Malaria afflicts 300 -500 million a year, killing nearly 3 million a year (largest killer in the world)

VI) Genetic Disorders B) Cystic Fibrosis: 1) Recessive disorder on chromosome #7 2) Mucous builds-up, making it difficult to breath & digest food; this allows bacteria to damage the linings of the lungs (often fatal by early adulthood) 3) Heterozygous carriers are more immune to not dehydrating from cholera, & recessives are immune to cholera 4) Cholera afflicts hundreds of thousand yearly, killing many thousands