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Do these genes make me look fat?
Transcript of Do these genes make me look fat?
The Department of Immigration wanted to see if people were actually related to those they were coming to live with.
Alec Jeffreys figured out that DNA could determine lineage and heritage
Types of Cases Analyzed in Forensic Biology
Clarification of Terminology
At first, they were called DNA Fingerprints
Utility of DNA at a crime scene
crime & catastrophe victims
endangered & protected species
prosecution of poachers
Exonerate wrongly accused
Establish paternity & familial relationships
Detect bacterial & other organism-based polutants to air, food, water, & soil
Do these genes make me look fat?
The rape and murder of a 15 year old schoolgirl named Lynda Mann horrifies the community.
the only forensic clue? semen
because of the location of the attack on a secluded footpath, police suspected a local
case goes unsolved
A 15 year old girl named Dawn Ashworth is found raped and murdered on a similar footpath
a computer search of local persons with prior sexual offenses identifies a suspect
that suspect, Buckland, makes a full confession
police ask Jeffreys to compare Buckland's DNA to sample found on Mann's body
it's not a match
police canvas the area and obtain samples from men in the area
find a match
So what exactly happens when we "send DNA to the lab"?
But now, we call them DNA Profiles
Now we refer to the process of individualizing DNA to a specific person as a DNA Profile
1985 investigation into the structure of a human gene led to the discovery that portions of the DNA structure of human genes are as unique to each individual as fingerprints. Alec Jeffreys and his colleagues at Leicester University in England coined the process for isolating and reading these DNA markers DNA Fingerprinting. As this became old technology – so did that term.
1987 saw the first conviction based on DNA evidence of Colin Pitchfork
wait ... what's poaching?
poaching means people who are hunting particular species outside of season
In 2011, the nation’s laboratories received 241,575 cases for DNA testing, a 16.4-percent increase from 2009. The total number of cases to be worked in 2011 was 343,422
Finally ... a use for those presumptive tests
Where is the stain?
What is it?
body fluid detection
body fluid identification
is it human?
What is the genetic profile?
determined through human specific DNA analysis
the size of sample needed to perform DNA analysis has decreased as technological advances have improved. see that speck? me neither!
So how much sample does it take?
Why do DNA analysis?
DNA was brought into the legal forum initially with immigration testing to prove biological relationships; paternity testing was not far behind
a familiar case is Thomas Jefferson and the reported relationship he had with his help
microbial identifications provide information that can let us know what you were feeding your toxic poisonous microbes like ricin, anthrax, tulurinia
the events of September 11th changed a lot in terms of what we do with DNA
remember that missing persons database? there is a database comprised of samples provided by family members seeking their loved ones lost as a result of this event.
the military used the "dog tag" method of identification for many years
this became impractical due to the nature of many of the injuries sustained by our heroes
now, a buccal (cheek) swab provides all that is needed for DNA identifications
remember that Locard guy??
hi! i'm anthrax
DNA is a chemical substance found in our bodies
responsible for determining all aspects of our physical makeup
same in almost every cell
stable over time and within the body
located in all cells (except red blood cells)
chromosomes are passed down from both parents
X Y - you're a guy!
DNA in the cell
the forensically relevant region is the 0.1% of our DNA that is different from one another
There are 2 types of DNA in each cell:
Most DNA in people is identical
but that 0.1% ...
So what is DNA?
the bands on the chromosomes identify where different characteristics are located
as you can see, there are more mitochondria in a cell, so there's more likelihood of mitochondrial DNA being present
it's that 0.1% that's different that determines individual features and is the forensic area of interest
99.9 % if you want to get technical
organized genetic material found in the cell nucleus
we have 23 pairs (or 46 total)
1 copy from mom
1 copy from dad
variant forms of genetic information (DNA) at a single locus
(because you have contributions from mom and dad)
combination of types obtained for multiple loci
the location of a gene or DNA marker in a non-coding region on a chromosome
(plural = loci)
an allele is a physical feature - something like eye color. my mom's eyes are green and my dad's eyes are brown - mine are brown. this is the 0.1% variation in the population's DNA
Short Tandem Repeats (STRs)
STR technology is used to evaluate specific loci within nuclear DNA
variability in STR regions can be used to distinguish one DNA profile from another
a standard set of loci evaluated prior to entry into CODIS is 13. the odds two individuals will have the same 13-loci profile is about one in a billion.
one locus will have 2 genes: one from mom and one from dad.
let's say mom's contribution is shown on top and dad's is on bottom. since this locus has different numbers of repeats, it's a heterozygote.
homozygote: both alleles are the same length
heterozygote: alleles differ and can be differentiated from one another
this process is repeated 13 times at 13 different loci
during DNA extraction/isolation
a series of chemical treatments to purify DNA from the body fluid
So what's the process?
during DNA quantitation
calculation of the amount of DNA extracted from the sample occurs
multiple methods exist
kinda like separating the yolk from the white of the egg? where the yolk is the DNA that we want and the white is the goop of body fluid that we're not interested in
Polymerase Chain Reaction (PCR)
this is where DNA is copied
no testing is involved
PCR cuts out the junk DNA and multiplies the good part we want to analyze (remember STRs?)
Forensic Short Tandem Repeat (STR) Analysis
this is where the products of the PCR (copying) process are analyzed using Capillary Electrophoresis (CE)
Profile is determined by comparing samples to standards
what we're looking at is homo vs. hetero samples.
we quantify based on the peaks - if they are short, we have a heterozygous sample. if they are tall, we have a homozygous sample.
since there is a tall peak (or a 'double') at the Amel locus, this is a female sample.
So what do we do with all this information?
The Combined DNA Index System (CODIS) is a DNA Databank software program that operates on a Local, State and National Level
it's used to link serial crimes and unsolved cases with repeat offenders
it creates a databank that can be used to search DNA profiles obtained from crime scene evidence
remember how we talked about cell structure? and that there were more mitochondria in each cell than there were nuclei?
1 copy per cell
multiple copies in each mitochondria
multiple mitochondria in each cell
so what's the big deal about mitochondrial DNA?
well ... it only comes from the mother.
when the sperm implants on the female egg, the tail drops off.
mitochondrial DNA is located in the tail. this is why you don't get any mitochondrial DNA from your father.
we can trace maternity through mitochondrial DNA - but not paternity
when you look at this evidence, column 4 is the indicator to let you know the test worked correctly.
columns 1-3 are samples from your victim and 2 suspects.
columns 5 and 6 are from your evidence.
so who can you NOT exclude as a suspect?
A. suspect A
B. suspect B
Which suspect cannot be excluded?
a closer look at deoxyribonucleic acid