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Lecture 17

Anthropology 2235A/B Lecture Notes - Lecture 17: Genetic Variation, Population Genetics, Product Rule


Department
Anthropology
Course Code
ANTH 2235A/B
Professor
Eldon Molto
Lecture
17

Page:
of 1
Lecture 17 Developing and Interpreting a Profile
Long tradition in forensic based on discernible uniqueness
Need to quantify all variation
E.g., a forensic odontologist finds 5 ante and postmortem agreements and
calls a match (what is the chances of each occurring in the population that
the individual comes from?)
They do not have these data
To develop a DNA profile there are a large number of complicated steps to
follow 1st
Individualizing a person based on their DNA (STR) profiles
o D13S317 11,12 24% of the population
o D7S820 10,11 4% of the population
o D8S1179 14,15 - 0.6% of the population or 1 out of 167 people
o Because each of the STRs is independent of each other basically
because they occur on different chromosomes the product rule can
be used whereby the relative frequency of each of the 13 STRs
Meaning and Statement of a DNA Match
o Approximately 1 person in every 10 trillion chosen at random from
the population would be expected to possess the same DNA
genotype as that found in the semen
o The DNA results are 10 trillion times more likely if the semen
originated from the suspect than if it had originated from a randomly
chosen unrelated individual from the population
o The DNA profile from Exhibit A matches the known sample from the
individual X, at 9 STR loci. The probability that a randomly selected
individual unrelated to individual X would coincidently share this
partial profile is estimated to be 1 in 74 million using the Caucasian
database
o Must be able to estimate the frequency of occurrence of the DNA
genotype in the relevant population
o Need to study population genetics
Population genetics is concerned with how much genetic
variation exists in natural populations and explains its origin,
maintenance and evolutionary importance
Genetic variation: no two individuals, except identical twins,
would be expected to possess the same genotype for all
genes