Topic 4 Flashcards
(9 cards)
The Frequency of a Multilocus Genotype in a Population (PMG)
PMG or the frequency of a multilocus genotype is equal to the product of the individual genotype frequencies
What Happens When We Use Highly Variable Loci?
The more variable a locus is, the lower the probability of observing a specific genotype at that locus.
This, of course, depends on the allele frequencies being relatively uniformly distributed (we don’t want the frequency of one allele to be 0.99, and the sum of the rest to be 0.01)
We previously regarded hyper-variability as a problem, but now its what we want!
What Happens When we Add More Loci?
The more loci we add, the probability of observing any specific multilocus genotype will be lower.
Why: We add more possible combinations of individual genotypes to the multilocus genotype.
The probability of observing a multilocus genotype is the product of each individual genotype frequency
What Do We Need to Have Now?: Background Data
We need to have screened a VERY LARGE number of individuals from the population, selected many loci that are variable, and have relatively uniformly distributed allele frequencies
The Combined DNA Index System (CODIS)
In the US, the DNA data set used is the CODIS system. It was developed by the US Federal Bureau of Investigation. Canada accesses this database. Currently, the data base contains DNA fingerprints (multilocus genotypes) from over 14,000,000 individuals.
20 Core u-sat loci are required for inclusion in this database. Prior to 2017, 13 core loci were included
The Canadian National DNA Data Bank
In 1998, parliament passed legislation to allow judges to order individuals convicted of serious offences to submit DNA samples so that their profile can be entered into the National DNA Data Bank.
The database now contains profiles for over 600,000 Canadians and has resulted in numerous additional convictions
Requirements: The Loci Used Must be In HW Equilibrium
We must ensure that there is no evidence for deviations from Hardy-Weinberg expectations at any locus.
We Require One More Property:
No Gametic Disequilibrium Among Loci
Each Locus Must Provide Us With:
AN INDEPENDENT ASSESSMENT
A Related Topic: Paternity Analysis
- Highly variable microsatellite loci can also be used to establish who the actual father of a child is.
- These markers are biparentally inherited, with one allele coming from the mother, the other from the father.
- In the case of paternity, if a child does not possess one allele present in the putative father at every locus, the putative father is not the actual father
