genes

• – genes on the same chromosome won’t necessarily undergo independent assortment
• -the closer together on the chromosome the greater the linkage between genes
• -the likelihood of recombination occurring between two genes increases with distance between genes

• – rare as there are very few genes on the Y-chromosome
• -Y-linked disorders are passed on to male offspring only (100%)

– males only receive a single copy of the X-chromosome (from their mother)

– offspring (female) have only a single X chromosome resulting from nondisjunction

– offspring (male) have an extra X chromosome resulting from nondisjunction

– a single base substitution

– point mutation leading to a codon coding for a different amino acid

– point mutation leading to a premature stop codon

– insertion or deletion leading to a change in the reading frame of a gene

– low level of ‘natural’ mutations that occur during replication (random error)

– metabolic disorders caused by mutation (usually of a key enzyme)

– an agent that causes mutation

an agent that can cause cancer (most are mutagens)

allele frequencies remain constant in a gene pool for a population in equilbrium

• p + q = 1
• p = frequency of dominant allele
• q = frequency of recessive allele

• p2 + 2pq + q2 = 1
• p2 = frequency of homozygous dominant genotype
• 2pq = frequency of heterozygous genotype
• q2 = frequency of homozygous recessive genotype

– crossing a dominant phenotype individual with a recessive to determine the dominant genotype

– crossing a hybrid (such as the F1) with one of the parents