2 Traits With Dominance 2 Traits With Dominance (pp 185-186)(pp 185-186)

Identify alleles Identify alleles (letters)(letters)

Write out crossWrite out cross Set up Punnett SquareSet up Punnett Square

4 possible gametes for 4 possible gametes for each parenteach parent

16 square Punnett 16 square Punnett SquareSquare

Fill in Punnett SquareFill in Punnett Square Give ResultsGive Results

       

       

       

       

Set C- 2 Traits With Set C- 2 Traits With DominanceDominance

T=Tall, t=ShortT=Tall, t=Short R=Round, R=Round,

r=Wrinkledr=Wrinkled TtRr x TtRrTtRr x TtRr Possible gametesPossible gametes

Male- Male- TR, Tr, tR, trTR, Tr, tR, tr

Female- Female- TR, Tr, tR, trTR, Tr, tR, tr

TR Tr tR tr

TR        

Tr        

tR        

tr        

Set C- 2 Traits With Set C- 2 Traits With DominanceDominance

TtRr x TtRrTtRr x TtRr Pheno-Pheno-

9 Tall Round9 Tall Round 3 Tall Wrinkled3 Tall Wrinkled 3 Short Round3 Short Round 1 Short Wrinkled1 Short Wrinkled

This is a dihybrid cross This is a dihybrid cross (hybrid for 2 traits)(hybrid for 2 traits)

Phenotype will always Phenotype will always be 9:3:3:1be 9:3:3:1

TR Tr tR tr

TR TTRR TTRr TtRR TtRr

Tr TTRr TTrr TtRr Ttrr

tR TtRR TtRr ttRR ttRr

tr TtRr Ttrr ttRr ttrr

Set D- Incomplete Dominance Set D- Incomplete Dominance p 184 p 184

Neither allele dominates Neither allele dominates otherother

White x White = WhiteWhite x White = White Red x Red = RedRed x Red = Red White x Red = PinkWhite x Red = Pink Offspring is a mix of 2 Offspring is a mix of 2

traitstraits Phenotype will be the Phenotype will be the

same as the Genotypesame as the Genotype RR = redRR = red rr = whiterr = white Rr = pinkRr = pink

Codominance p 184Codominance p 184

Both alleles are Both alleles are expressedexpressed

BB = blackBB = black WW = whiteWW = white BW = black & whiteBW = black & white Black feathers x Black feathers x

white feathers = white feathers = black and white black and white feathersfeathers

Set E- Sex DeterminationSet E- Sex Determination

Sex ChromosomesSex Chromosomes Determines sexDetermines sex X & Y chromosomesX & Y chromosomes Males = XYMales = XY Females = XXFemales = XX Humans = 2 (1 pair)Humans = 2 (1 pair)

AutosomesAutosomes All other chromosomesAll other chromosomes Humans = 44 (22 pair)Humans = 44 (22 pair)

Karyotype- shows Karyotype- shows chromosomes (see chromosomes (see page 236) page 236)

Set F- Sex Linked TraitsSet F- Sex Linked Traits

Determined by Determined by recessive alleles recessive alleles located on the “X” located on the “X” chromosomechromosome

Occur more often Occur more often in males (need only in males (need only 1 recessive allele)1 recessive allele)

Ex. male = XEx. male = XnnY Y Ex. female = XEx. female = XnnXXnn

Set F- Sex Linked TraitsSet F- Sex Linked Traits

Possible genotypesPossible genotypes Normal Male = XNormal Male = XNNYY Male with trait = XMale with trait = XnnYY Normal Female = XNormal Female = XN N XXNN

Carrier Female = XCarrier Female = XNNXXnn

Female with trait = XFemale with trait = XnnXXnn

Set G- Multiple AllelesSet G- Multiple Alleles

More than 2 alleles for a More than 2 alleles for a trait (in the populations trait (in the populations gene pool)gene pool)

Each individual will still Each individual will still have only 2 alleles for the have only 2 alleles for the traittrait C = full colorC = full color h = himalayanh = himalayan a = albinoa = albino

Example- some rabbitsExample- some rabbits CC, Ch, or Ca = full colorCC, Ch, or Ca = full color hh, ha = himalayanhh, ha = himalayan aa = albinoaa = albino

Set H- Human Blood TypeSet H- Human Blood Type

Multiple allelesMultiple alleles A, B, OA, B, O

DominanceDominance A & B dominant to A & B dominant to

O O CodominanceCodominance

A & B codominant A & B codominant to each otherto each other

Set H- Human Blood TypeSet H- Human Blood Type

TypeType GenotypeGenotype AA

AA, AOAA, AO BB

BB, BOBB, BO ABAB

ABAB OO

OOOO

Genetic DisordersGenetic Disorders

Huntington disease-Huntington disease- Caused by a single Caused by a single

dominant allele (H)dominant allele (H) Sickle cell anemia-Sickle cell anemia-

Autosomal recessiveAutosomal recessive Colorblindness (red–Colorblindness (red–

green)-green)- Sex linked trait, recessive Sex linked trait, recessive

allele on X chromosomeallele on X chromosome

Genetic DisordersGenetic Disorders

Hemophilia-Hemophilia- Sex linked trait, recessive Sex linked trait, recessive

allele on X chromosomeallele on X chromosome Down syndrome-Down syndrome-

Nondisjunction of 21Nondisjunction of 21stst pair pair of chromosomesof chromosomes

No disjunction- failure No disjunction- failure of chromosomes to of chromosomes to separate during separate during meiosismeiosis