What is genetics concerned with at a population level?
Why is this helpful?
1- At a population level genetics is concerned with allele frequencies, that is, how often a particular allele is found in a population.
2- Understanding the frequency of alleles in a population allows us to make informed estimates of a person's genotype even without knowing a lot of other information. This data can be used to predict rates of genetic disease and to identify persons through genetic profiling
Give an example of genetics at a population level?
Ex) the allele for black hair is for more common in Asia that in Scandinavia while the allele for blue eyes is just the opposite
What is a population?
A group of members of the same species in a given geographical area who are potentially capable of mating and producing fertile offspring.
What is a gene pool?
A gene pool represents all of the possible alleles present in the population.
What is a gene flow?
A gene flow is when alleles can move between populations when individuals migrate or mate
What is population genetics?
Population genetics deals with the flow of genes, and often encompasses more than just science
For genotype frequencies to remain the same, all of the following must occur: (5)
*Is this common?
1- Mating must be random
2- Individuals must not migrate between populations
3- The mating population must be very large
4- Mutations must not occur
5- All genotypes must be equally successful
*Most cases genotypic frequencies DO NOT stay the same, but the frequency of some alleles does in fact remain constant
What is the Hardy-Weinberg Equilibrium equation? What does each component mean?
p + q =1
p= dominant allele
q= recessive allele
What is the second Hardy-Weinburg equation?
p^2 + 2pq + q^2= 1
In other words, all of the homozygous dominant individuals (p2) plus all of the homozygous recessive individuals (q2) plus all of the heterozygous individuals (2pq) equals 100% of the possibilities
p^ 2 +2pq+ p^2= 1
What is so unique about this equation?
The p accounts for all the dominant alleles
The q account for all of the recessive alleles.
we can then use this to find all of the heterozygotes in the equation (2pq)
If p is 0.7, what is q?
What is the heterozygote rate?
q is .3
Heterozygote rate= (2)(.7)(.3)= .42
Thus 42 percent
If 1 in 2000 European descents have cystic fibrosis (autosomal recessive), what is the frequency?
square root of 0.0005= .022
(2) (.022) (0.978)= 0.043= 1/23
For rare disorders, where the frequency of q is very low (and the frequency of P is consequently very close to 1) the Hardy Weinberg equilibrium can be simplified. In cases such as this the carrier frequency is approximately twice the frequency of q (in other words 2q)
What is DNA profiling? How does it it use the Hardy Weinburg assumption?
DNA profiling aka DNA fingerprinting uses HW for the analysis.
The technique relies on determing the number of copies of a small repeated sequence carried by an individual. These
repeats are 20-80 bases long. These repeats can be considered an allele
What is the possibility of having 6 repeats on DNA profiling?
The probability of randomly having 6 repeats (i.e. matching that seen at a crime scene) is found by multiplying the probability of having each individual fragment
How is DNA from skin or blood separated?
DNA, recovered from skin or blood left at a crime scene, is separated by size using gel electrophoresis
What is the chance of someone having the same DNA fragments .36, .30, .24, .04, and .29
The chance of a person having the set of DNA fragments seen here is 0.36 x 0.30 x 0.24 x 0.04 x 0.29 = 0.00031 or 1/3,226
8 challenges to DNA profiling in Mass Disasters
1- Climate that hastens decay
2- Inability to reach remains
3- No laboratory facilities
4- Number of casualties
5- Lack of relatives
6- Destruction of personal item evidence
7- Poor DNA quality (too fragmented, scarce, degraded)
8- Lack of availability of DNA probes and statistics for population.