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

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

R WW RR R W W RW Genotypes –RR: 1 –RW: 2 –WW: 1 Phenotypes –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 W = White RW = Roan (Red/White) R = W Roan X Roan Horse Cross

R WW RR R W W RW Genotypes –RR: 1 –RW: 2 –WW: 1 Phenotypes –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 i B > i i A = i B i A i A or i A i = A-Blood i B i B or i B i = B-Blood ii = O-Blood i A i B = AB-Blood Cross a heterozygous A- blood man with a heterozygous B-blood woman

iBiB ii iAiBiAiB iAiA i i i A i i B i Genotypes –i A i B : 1 –i B i: 1 –i A i: 1 –ii: 1 Phenotypes –AB Blood: 1 –B 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 > X C Y plays no part XX = Normal ♀ XX C = Carrier ♀ X C X C = Colorblind ♀ XY = Normal ♂ X C Y = Colorblind ♂ Cross a carrier ♀ with a normal ♂

X XCYXCY XX X Y XCXC XY XX C Genotypes –XX: 1 –XX C : 1 –XY: 1 –X C Y: 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 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