linkage and mapping

human genetics lecture 3

polymorphism

presence of two or more alleles for the same gene that can occur among different individuals or populations

single nucleotide polymorphism (SNP)

genomic variant at a single nucleotide position in DNA

haplotype

physical grouping of polymorphisms that tend to be inherited together

synteny

when different genes are on the same chromosome

chi square tests

find the probability that the difference between the observed and expected is due to chance alone

degrees of freedom

number of alternate outcomes compared to the expected

α-value

threshold for rejecting the null hypothesis

p-value

probability of getting results at least as extreme as those observed, assuming the null hypothesis is true

high p-value

differences are likely due to chance

low p-value

differences are likely not due to chance

complete genetic linkage

observed when no crossing over occurs, only parental gametes are formed

incomplete genetic linkage

mixture of parental and nonparental gametes are produced

recombination frequency (r)

reflects the physical distance between two genes

r=0.5

genes are completely unlinked

r<0.5

genes are linked

formula for recombination frequency (r)

r = number of recombinant animals / total number of animals

linkage map

plotting of the relative position of genes along a chromosome

units of distance between genes

centiMorgan (cM) or map units (mu)