Hardy Weinberg in Human population and forensic genetics Flashcards
HWE
no human population can meet all the requirements of HW law but can still use to calculate genotype proportions
significant deviation
Various tests have been carried out on population data comparing predicted genotype frequencies under HWE and measuring if there is significant deviation
Significant deviations have not been detected in the vast majority of population
forensic DNA analysis
the HWE is used along with allele frequency databases to calculate genotype frequencies
recessively inherited disorders
HW law can be used to calculate the frequencies of harmful recessive alleles
Homozygote recessive disorder such as cystic fibrosis
what do AA, Aa and aa represent
AA=normal phenotype
Aa=carrier
aa=disease phenotype
what does p+q equal
1
A + a is the same as what
p+q
what are AA, Aa and aa in p and q terms
AA = p squared Aa = 2pq aa = q squared
what is the frequency of heterozygous carriers
2pq
e.g 1 in 1000 children has cystic fibrosis, what is q squared, q, p and 2pq
q squared = 0.001
q = 0.03
p = 0.97
2pq = 0.0582
allele frequency databases
constructed by measuring the occurrence of alleles within a defined population
It has been recommended that a sample of at least 200 alleles per locus (100 individuals) is used
frequencies of STR profiles
The genotype proportions for each locus are calculates using p2 for homozygotes and 2pq for heterozygotes
The overall profile frequency is calculated by multiplying the genotype frequency at each locus
This is called the product rule
the product rule
Multiplication of individual genotype frequencies at different loci to give the overall profile frequency
Population must be in linkage equilibrium
This is true for the standard STRs
All on different chromosomes & are inherited independently
see powerpoint for
calculation of STR profile frequency
