OTHER PATTERNS OF INHERITANCE

Law of Independent Assortment Mendelian Genetics 4/27/2017 Law of Independent Assortment Alleles for different traits are distributed to sex cells (& offspring) independently of one another.

Trait determined by a gene on a sex chromosome (usually X). Sex-Linked Traits Trait determined by a gene on a sex chromosome (usually X). Examples: Colorblindness Hemophilia Muscular Dystrophy

Females with only 1 affected X are carriers. Sex-Linked Traits: *Females must receive 2 affected X’s in order to express the trait. Females with only 1 affected X are carriers. Males that receive one X from mother expresses the trait.

Sex-Linked Punnett Square Practice Cross a colorblind mother with a father who has normal vision: Give the genotypic and phenotypic ratios. Key: XcXc = colorblind mother XY = normal vision father Cross: XcXc (x) XY Genotypic Ratio: Phenotypic Ratio: Xc X Y Answer on next slide…

Sex-Linked Genotypic Ratio: 2:4 XcX 2:4 XcY Phenotypic Ratio: Mendelian Genetics 4/27/2017 Sex-Linked Key: XX = female XY = male Cross: XcXc (x) XY X Y Xc Xc Genotypic Ratio: 2:4 XcX 2:4 XcY Phenotypic Ratio: 2:4 Carrier Female 2:4 Colorblind Male XcX XcY

Polygenic Traits “Many genes” ; Many traits are controlled by more than one gene; have a variety of choices for expression. Ex: _hair color, eye color, skin tone___

Multiple Alleles Genes that have more than 2 alleles Ex: blood group. There are 3 possible alleles for this gene. i ii

Blood Type Punnett Square Practice Cross a female who is Type AA with a male who is Type O (ii): Give the genotypic and phenotypic ratios. Key: AA = mother ii = father Cross: AA x ii A Genotypic Ratio: Phenotypic Ratio: i Answer on next slide…

Blood Type Genotypic Ratio: 4:4 Ai Phenotypic Ratio: 4:4 Type A Blood Mendelian Genetics 4/27/2017 Blood Type Key: AA = female ii = male Cross: XcXc (x) XY i A A Genotypic Ratio: 4:4 Ai Phenotypic Ratio: 4:4 Type A Blood Ai

Mendelian Genetics 4/27/2017 Incomplete Dominance Neither allele has “complete” dominance over the other; heterozygous phenotype is a blend of the 2 homozygous phenotypes Ex: snapdragons R = red W = white RW = pink

Incomplete Dominance Cross a red (RR) snapdragon with a White (WW) snapdragon. Give the genotypic and phenotypic ratios. Key: R = red flower W = white flower Cross: RR x WW Genotypic Ratio: Phenotypic Ratio: W R Answer on next slide…

Incomplete Dominance Genotypic Ratio: 0RR: 4RW: 0WW Phenotypic Ratio: Mendelian Genetics 4/27/2017 Incomplete Dominance Key: R = red W = white Cross: RR x WW R W W Genotypic Ratio: 0RR: 4RW: 0WW Phenotypic Ratio: 0 Red: 4 Pink: 0 White RW

Mendelian Genetics 4/27/2017 Incomplete Dominance Practice: Cross a pink snapdragon with a red snapdragon. Give the expected phenotypic and genotypic ratios. Key: __________________ Cross: _________________ Genotypic Ratio: ________________________ Phenotypic Ratio: ________________________

Incomplete Dominance R R R RR RR W RW RW Mendelian Genetics 4/27/2017 Incomplete Dominance Practice: Cross a pink snapdragon with a red snapdragon. Give the expected phenotypic and genotypic ratios. R R Key: R = red W = white RW = pink Cross: _RW x RR__ Genotypic Ratio: __2RR: 2RW: 0WW__ Phenotypic Ratio: __2 red: 2 pink: 0 white_ R RR RR W RW RW

Mendelian Genetics 4/27/2017 Codominance Codominance – Both alleles share dominance and are always expressed if present. Ex: In chickens B = black feathers W = white feathers BW = black AND white feathers X

CODominance Cross a black (B) rooster with a white (W) chicken. Give the genotypic and phenotypic ratios. Key: B = black feathers W = white feathers Cross: BB x WW Genotypic Ratio: Phenotypic Ratio: W B Answer on next slide…

CODominance Key: B = black W = white Cross: BB x WW B W W BW Mendelian Genetics 4/27/2017 CODominance Key: B = black W = white Cross: BB x WW B W W Genotypic Ratio: 0BB: 4BW: 0WW Phenotypic Ratio: 0 black: 4 black and white: 0 white BW

Mendelian Genetics 4/27/2017 CODominance Practice: Cross two black and white feathered chickens. Give the expected phenotypic and genotypic ratios of the offspring. Key: __________________ Cross: _________________ Genotypic Ratio: ________________________ Phenotypic Ratio: ________________________

CODominance B W B BB BW W BW WW Mendelian Genetics 4/27/2017 CODominance Practice: Cross two black and white feathered chickens. Give the expected phenotypic and genotypic ratios of the offspring. B W Key: B = black W = white BW = black and white Cross: _BW x BW__ Genotypic Ratio: __1BB: 2BW: 1WW_ Phenotypic Ratio: _1 black: 2 black and white: 1 white_ B BB BW W BW WW