Lecture 13, 14, & 15 Flashcards
Population Genetics
You’ve generated some genotypes, now what do you do?
(consider logic of two sample comparison and desire to know if they have common source)
What are the three possible results from a comparison of two samples?
- match = failure to exclude
- no match = exclusion
- neither = failure 2 reach conclusion
What is the theoretical basis of how to determine how common a genotypic profile is
Population genetics- RMP
What is an example of a population genetic parameter?
Proportion of a particular allele
2 alleles per person
Frequency
count, not fraction, whole number
Proportion
frequency / total
What does the big number vs subscript represent?
Big number = locus, subscript= allele variant
Formula for allele proportion
Add picture
What does the capital P and lowercase p stand for in equation?
Lowercase p= allele proportion
Uppercase= genotype proportion
How to calcuclate P(homozygous)
Count of individuals with that genotype over total population
How 2 calc (1/2)(sum of P(heterozygous))
find the genotype from all the potential heterozygotes, and multiply it by 0.5
How to solve this or that?
Sum of their probabilities
How to solve this and that?
Multiplication of the probabilities
If they are statistically independent, how can you solve the “and” probability?
By multiplying the individual probabilities without their condition
What is the probability that you roll a one and a two but doesn’t matter what order
2/36
1/36 + 1/36
P(1,2) + P(2,1)
What is Hardy Weinberg equilibrium
stat independence of alleles at one locus
!expected genotype frequencies as a function of allele frequency
What is Linkage Equilibrium
implication of statistical independence of separate loci
What does HWE stand for
Hardy Weinberg equilibrium
What are conditions of HWE?
large pop
random mating
no… genetic drift/NS
Genotype probability for homo and hetero
homo = p(allele)^2
hetero = 2(p1)(p2)
(small p = proportion)
How do you find observed allele frequency from genotype frequency?
p^2 + (0.5*2pq)
so… the homozygous genotype frequency for that allele PLUS half of the heterozygous genotype frequency
For exam, be able to determine if population is in HWE
By comparing counts from expected to actual
- What does the HW equation tell you about the population? (IMP for exam?)
expected genotype proportions as a function of allele proportions
He will give the counts and ask if the population is in HWE… What are the steps to doing this?
from counts, calculate allele proportions byyyyy:
1.Take counts, divide by total pop
2. Find allele frequencies by adding the homozygous with half the heterozygous.
3. Use HWE to find genotype proportion by squaring allele proportion and 2pq.
4. Then multiply by total pop and it should match the og counts if it is in HWE.
How do you immediately know it is not in HWE
No homozygous or
No heterozygous
