Bellringer Problems: PKU. Bellringer Problems: Huntington’s Disease.
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Bellringer Problems: PKU
Transcript of Bellringer Problems: PKU. Bellringer Problems: Huntington’s Disease.
Bellringer Problems: PKU
Bellringer Problems: Huntington’s Disease
Bellringer Problems:CF
Non-Mendelian Genetics
Modifications to the expected Mendelian ratios…
For example – in snapdragons, cross a red flowered plant with a white flowered plant…
Mendel predicted you would end up with…
But he was wrong…
You get all *pink* flowers!
Why?
R = red and r = white
Red x white Pink x Pink
Incomplete Dominance
Incomplete Dominance
Intermediate phenotype in heterozygotes…
It is a “blend” between the dominant and recessive forms of the gene
Sample Problem
In horses, the dominant D allele allows coat color to fully develop. The d allele dilutes, or weakens, coat color. When a chestnut (brown) horse is crossed with a cremello (nearly white) horse, their offspring are palominos (gold with white manes and tails)
Sample Problem Continued
What is the genotype of…• A chestnut horse? ______________• A cremello horse? ______________• A palomino horse? ______________What would be the expected
phenotypic ratios of a cross between two palomino horses?
Another example from your dragons…
The case of the missing purebred…
Manx cats are born tailless. But if you cross two Manx cats you will never get 100% Manx kittens. Never ever ever.
Lethal Alleles
Lethal Alleles
The homozygous condition is lethal…
Sample Problem
Achondroplasia, a form of dwarfism, is caused by the dominant allele A. Embryos with the genotype AA do not survive. Suppose that two people with achondroplasia get married and have children.
What phenotypic ratio would you observe in the couple’s children?
The case of the orange cows…
In cattle, red hair is dominant to white hair…but when you cross a red bull with a white cow, you get…
ROAN CATTLE
Codominance
Definition:
Codominance
• BOTH alleles are expressed at the same time
• Heterozygous = both phenotypes expressed equally
R = red and R’ = white
Red x white Roan x Roan
Practice Problem
Andalusian chickens– Black feathers is codominant with white
feathers– Heterozygous = __________________________
It’s a guy thing, you wouldn’t understand…
Sex-linked
Definition:
Sex-linked
Pattern of inheritance for genes located on X (sex) chromosome. Rarely on Y…
Sex-linked Genes
Example: ColorblindnessXB, Xb, YGenotypes? Phenotypes?
Practice
Colorblindness:Normal Male x Carrier Female
Genotypes Phenotypes
Sex-linked Genes
Example: HemophiliaXH, Xh, YGenotypes? Phenotypes?
Practice
Hemophilia:Hemophiliac Male x Carrier Female
Genotypes Phenotypes
Blood Types
