Flashcards in 9 21 Genetics and genome sequencing-Table 2 Deck (13):
sugar loaf area
saline solution code
what is the DNA that is actually used for forensic analysis
Short tandem repeats
what is a short tandem repeats?
non-coading repeats, that are repeated sections of short repeating aleales: i.e. cacacaca....
how is PCR used to define an individual's DNA profile?
design primers that are specific to one genome spot on either side of a repeat and then copy out the repeat and amplify it. The region between the primers will be variable, while the primers will be constant between individuals.
what is CODIS?
they are specifically chosen short tandem repeats (combined DNA index system)
how do you analze the CODIS?
you take the sample, and PcR to make millions of copies of the STR. then use electrophoresis to separate the DNA fragments by size (neg. DNA travels farther when smaller) then the pattern of stains on the gel indicates a specific length set of STRs
what is a electropherogram and what does it show us?
It shows a linear graph of size of repeates...basically a horizontal picture of the bands on the gel, it shows the size of an allele. usually 2 peaks per allele to show the maternal and paternal alleles
what does the amelogenin marker tell us
the gender of the individual, if there are two peaks then there are two sized allelels therefore a boy!
how do you use hardy-weinberg est. in crime scene DNA evidence?
We want to know the genotype probability (2pq) for the specific profile seen by an individual in the population. then when we use multiple genotype markers we can use the 'and' rule of probability and multiply the different 2pq numbers together to get a total prob. of having a specific sequence again.
why not use Hardy Weinber est. in paternity analysis?
because in paternity we are using gene frequency or allele frequency because we are just looking at the paternal, we already know the maternal, so we want just p, or just q and not 2pq!
what are some of the issues of DNA sample?
was the DNA sample collected, processed and analyzed properly? (chain of custody, DNA contamination, appropriate data analysis); rerfernce population appropriate? expert witness really an expert?