Presentation on theme: "Gentoypes and Phenotypes Monohybrid Crosses Dihybrid Crosses."— Presentation transcript:
Gentoypes and Phenotypes Monohybrid Crosses Dihybrid Crosses
In certain breeds of dogs, deafness is due to a recessive allele (d), and normal hearing is due to its dominant allele (D). What percentage of the offspring of a normal heterozygous (Dd) dog and a deaf dog (dd) would be expected to have normal hearing? Dd dDddd dDddd DD = normal Dd = normal dd = deaf 2/4 = 50%
In humans, normal pigmentation is due to a dominant allele (C), and albinism is due to it’s recessive allele (c). A normal man marries an albino woman. Their first child is albino. What are the genotypes of these three people? Dad had to carry the recessive allele to be able to pass it on to the child. If Dad had the genotype (CC), then every offspring would be (Cc), which would be normal pigmentation.
In minks, brown is dominant over silver- blue color. What are the possible genotypes for the offspring if you cross a homozygous brown mink with a silver-blue mink? bb BBb B
In snapdragons, red is not completely dominant over white flowers. What color flowers would you expect when you cross a red flower with a white flower? What would be the genotypic and phenotypic ratios of the offspring be? This is an example of Incomplete Dominance
RR x Rr = parent genotypes In cattle, a cross between a white (rr) and a red (RR) cow produces a roan colored cow. Cross a red-haired and roan colored cow. What are the genotypes of the parents? What are the phenotypic ratios of the offspring? RR RRR rRr RR to Rr = 2:2 50% Red 50% Roan
In humans, acondroplasia “dwarfism” (D) is dominant over normal (d). A homozygous dominant (DD) person dies before the age of one. A heterozygous (Dd) person is dwarfed. A homozygous recessive individual is normal.
Dd DDDDd d dd A heterozygous dwarf man marries a dwarf heterozygous woman. Give the genotypic ratio and the phenotypes of the possible offspring. 1:2:1 genotypic ratio 25% chance of a DD, homozygous dwarf which dies before the age of one 50% chance of having a dwarf child 25% chance of having a child with normal height
If Sponge Bob is heterozygous squarepants, homozygous yellow body: What is his genotype? SsYY Using the FOIL method, what would the 4 possible gamete combinations be? SY sY Sponge Bob Dihybrid Genetics (S = squarepants, s = roundpants; Y = yellow body, y = blue body)
If Sponge Susie is roundpants, heterozygous yellow body: What is her genotype? ssYy Use the FOIL method to find the 4 possible gamete combinations sY sy sY sy Sponge Susie Dihybrid Genetics
If Patrick is heterozygous tall head, heterozygous pink body: What is his genotype? TtPp Use the FOIL method to find his 4 possible gamete combinations TP Tp tP tp Patrick Dihybrid Genetics (T = tall head, t = short head; P = pink body, p= orange body)