Unformatted text preview: nset 4-6 months old s Lack of enzyme (Hex A) to break down fatty buildup in brain s Lethal (by age 5) s Incomplete Dominance- phenotype of heterozygote is intermediate between dominant & recessive trait. F1 = all pink Rr F2 - Phenotypic &
Genotypic ratios are the same = 1:2:1
R r RR rr Rr 14.19 s Relationship between genotype and phenotype Types of Variation is sometimes not so simple: x Multiple alleles
3 Blood groups: A, B alleles are codominant; O is recessive Types of Variation
s Relationship between genotype and phenotype is usually complex: x Pleiotropy - One gene may affect many traits.
3 the recent finding of unexpectedly few human genes 3 E.g. Coloration and crossed eyes in Siamese cats 3 Marfan syndrome One gene Pleiotropy: e.g., sickle cell Many symptoms s Epistasis gene at one locus alters the phenotype of a gene at another locus
x Very common x E.g. coat color in mice x E.g., Labrad...
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This note was uploaded on 05/11/2010 for the course BIOLOGY 100 taught by Professor Richard during the Spring '10 term at George Mason.
- Spring '10