Forensic DNA Processing Flashcards
What is forensic DNA analysis?
Individualization of biological substances to a certain person by DNA profiling
What is the nucleus?
(Cells)
Control center of the cell
What do nucleotides consist of?
- Phosphate group
- Pentose sugar
- Nitrogenous base
What are the properties of a hydrogen bond?
- Double strand
- A pairs with T
- G pairs with C
How similar is human DNA?
99.7% identical between people
What are genes, loci, and alleles?
Gene:
Segments of DNA that determine traits
Loci:
The position of a gene on the chromosome
Allele:
A variant form of a gene. Humans have 2 alleles at each genetic locus (one from mom, one from dad)
What are short tandem repeates (STR regions)?
A region of DNA that is composed of short sequences of nucleotides that repeat many times
The number of repeats in the same locus vary person to person
Ex. (AATG) with 7 repeats from mom and 8 repeats from dad
What is a homozygote vs a heterozygote?
Homozygote:
Both alleles are the same length
Heterozygote:
Alleles have a different length
What is CODIS?
Combined DNA Index System
National DNA database in the US that allows forensic labs to share and compare DNA profiles
Goes 20 loci deep
What are the steps of DNA analysis and their overarching functions?
DNA extraction:
Isolate DNA from cell
DNA quantification:
See how much was isolated
DNA amplification:
Grab the loci and make more
DNA seperation and detection:
Seperate and detect repeats
Data interpretation:
Is there a match?
What is the process of DNA extraction?
Isolating the DNA within the cell and extracting it. Getting rid of all unneccesary cell aspects.
Extraction procedures:
* Organic (Phenol-Chloroform) (toxic and slow, high yield)
* Chelex (Ion exchange Resin) (fast, cheap, lower yield)
* Solid Phase Extraction (SPE)* (fast, expensive, high yield)*
What is the purpose of differential extraction?
Purpose: To separately isolate the male and female DNA from sexual assault evidentiary samples
What is the purpose of DNA quantitation?
To measure the quality and quantity of DNA present in a sample
What are the steps of DNA amplification?
(ESSAY QUESTION KNOW THIS STUFF)
Polymerase Chain Reaction (PCR)
Making copies of an STR region
Steps:
1. Denaturation (heating samples to denature/seperate double stranded DNA)
2. Annealing (lower temp., and allow primers to anneal (recombine/bond)
3. Extension (Allow polymerase to elongate/extend the new DNA strands)
Each time the process is repeated, the DNA will double
What is the process of DNA seperation and detection?
- DNA is seperated again and bonded with a fluorescent primer
- DNA is run through a capillary electrophoresis machine
- Smaller fragments move faster and are detected first
The machine creates a STR profile
What are the characteristics of an STR profile?
Each profile has multiple STR loci markers with two alleles each
What are the three criteria of DNA interpretation?
Exclusion:
No match
Inclusion:
Match, cannot exclude
Inconclusive:
No result
What is the innocence project?
Using new DNA technology and evidence to help demonstrate innocense post-conviction
What is forensic genetic genealogy?
The use of DNA testing in combination with traditional genealogical and historical records to infer the relationship between individuals
What are centimorgans?
- Unit of genetic measurement. How much DNA and the
length of specific segments of DNA you share with
your relatives. - The total length of all your chromosomes combined is
around 7400 cM - You share about 3700 cM with each parent.
What are the types of DNA test for genealogy
Autosomal DNA:
The DNA inherited from every chromosome minus your X and Y
Y-chromosome DNA:
Passed from father to son
Mitochondrial DNA:
Passed from mother to children
X-chromosome:
Son = just from mom
Daughter = one from each parent
In other words:
Males inherit an X from their mother, a Y from their father, and mitochondrial from their mother
Females inherit an X from their mother, an X from their father, and mitochondrial from their mother
What are the types of records used to build family trees?
Vital records:
Birth, marriage, and death records
Draft registration records:
Important during WWI and WWII
Census records:
Collected every 10 years, released every 72 years
What is FIGG?
Forensic Investigative Genetic Genealogy:
Utilizing genetic information from direct-to-consumer companies for identifying suspects or victims in criminal cases
What are FIGG companies?
CODIS
AncestryDNA
UK DNA Database
23andMe
Myheritage
FamilyTreeDNA
GEDmatch
What are the types of FIGG tests?
Y-DNA:
* Looking at paternal lines
mtDNA:
* Passed through maternal lines
Autosomal DNA:
* Tracked in centimorgans
* FamilyTreeDNA
X-DNA:
* Useful for both males and females
* Can help include/exclude branches of the family
