Module 6 - Advances in Forensic Biology Flashcards
1
Q
What is forensics?
A
- refers to the study of evidence discovered at a crime scene
2
Q
What is forensic biology?
A
- refers to the analysis of genetics/and or other physical properties of evidence
3
Q
What is forensic biology and polymorphic markers?
A
- central part of forensic biology is to use DNA as a means of identifying individuals within a population
- such identification depends on polymorphic markers (DNA sequences that differ between individuals)
4
Q
What are the sources of DNA
A
- biological material used for DNA profiling include: blood, semen, saliva, urine, feces, hair, bone, teeth, tissue and cells
5
Q
What does autosomal inheritance mean?
A
- passed on in part, from all ancestors
6
Q
What does autosomal STR analysis mean?
A
- current marker that forensic casework uses
- STR = short tandem repeat
- 2-4 base pairs per repeat; number of copies of repeats makes allele
- typically found in non-coding regions of genome
- doesn’t affect phenotype
7
Q
Autosomal STR analysis (con’t)
A
- multiple alleles exist in population for each STR locus; the combination each of us has depends on genetic inheritance
- each person has a maximum of two different alleles; can have two copies of the same allele
- DNA is extracted from nuclei of DNA of interest
- loci to be examined are amplified by multiplex PCR
- PCR products are resolved with capillary electrophoresis; time it takes for fluorescently based PCR product to reach detector, indicate its length, and count the number of repeats
8
Q
What are the advantages of PCR?
A
- since PCR is used, very small amount of DNA is needed
- very sensitive (rarely any false matches)
9
Q
What are allele names for autosomal STR analysis?
A
- for a particular locus, allele names generally correspond to the number of repeats for that allele
10
Q
Example of a DNA profile
A
- height of peaks proportional to the number amount of DNA at the end (and start) of PCR rxn
- heterozygote: two equally sized peaks
- homozygote: one larger peak
11
Q
What is mitochondrial DNA?
A
- mitochondrial (mt) genome is distinct from nuclear genome
- mitochondrial genome is ONLY inherited from the mother; shows particular population distribution
- nuclear DNA is inherited from BOTH parents
- mitochondrial DNA is used in DNA profiling when biological samples are old
- around 200-1700 mitochondria are in each cell so the chances of survival for mitochondria in a cell is greater than nucleus
- usually, two hypervariable (polymorphic) regions called HVI and HVII are sequenced
- disadvantage: less diversity in population than nuclear markers
12
Q
What is Y chromosome STR analysis?
A
- most serious crimes are committed by men, so analyses of Y chromosome found at crime scenes are very helpful
- Y-specific profiling can be effective even when there is a 4000-fold of female DNA
- likelihood of 2 people having the same number of repeated sequences are very small, and become even smaller the more regions are analyzed
- 219 useful STR markers on the Y chromosome
- set of 9-16 are commonly analyzed in forensic investigations
13
Q
What are issues with DNA evidence?
A
DNA evidence can be unequivocal under ideal conditions:
- when a suspect’s genes are well preserved
- when its clear how the DNA arrived to the crime scene
- when the sequencing lab doesn’t make any mistakes
- a lot of cases where these conditions aren’t met
14
Q
Non-human species in forensic genetics
A
- analyses of animal DNA (eg. from pet hairs) can also be used in investigations
15
Q
Wild life forensics
A
- species identification
- individual identification
- gender typing
- population studies
