DNA Profiling Flashcards
How can DNA be important in criminal investigations?
DNA sequences are unique to everyone (except twins)
Variation within non-coding parts for the DNA molecule is the basis for forensic I.D.
Besides in criminal and other forensic cases, what are three other types of cases
that may utilize DNA profiling?
-Parentage
-Identification of disasters and war victims
-Resolution of historical and recent missing persons cases
what is the long name for DNA?
Deoxyribonucleic acid (DNA)
What is the purpose for DNA?
Contains genetic code for the production of proteins that enable a cell to replicate its DNA and carry on life functions.
Nucleotides consist of three parts. What are they?
-nitrogenous bases
-phosphate group
-pentose sugar molecule
What are the four nitrogenous bases that make up the helix ladder?
-adenine
-thymine
-cytosine
-guanine
What is the difference between exons and introns?
exons:
-will be expressed
-part of the coding regions
Introns:
-will be deleted
-not part of the coding region
What are autosomes? What are karyotypes?
Autosomes:The other 44 chromosomes that aren’t sex chromosomes, appear in homologous pairs
Karyotype: picture of the paired homologous chromosomes and sex chromosomes in a cell.
How are polymerase chain reactions (PCR) related to collecting DNA evidence?
A method of amplifying (duplicating) minute amounts of DNA evidence for
the use of investigations.
What is the downside to PCR?
Amplifying will also copy cross contamination as well as the DNA sample.
What are three ways to limit cross contamination when handling DNA?
-wear and change disposable gloves.
-Avoid touching areas where DNA may exist.
-Avoid talking, sneezing, and coughing around evidence.
What are three conditions that will damage DNA?
-humid
-warm
-bright
What are restriction enzymes?
“Molecular scissors”
-a molecule that cuts a DNA molecule at a specific
base sequence.
What are short tandem repeats (STRs)?
Sequence of repeating bases in noncoding regions of DNA that are used in DNA profiling
how are restriction fragments created?
in preparation for gel
electrophoresis
What happens during gel electrophoresis?
Restriction fragments are separated by size on a gel when an electric field is applied. Radioactive probes bond to the highly variable regions, creating a unique band pattern.
How could a STR pattern be different between two people?
For example, one person could have a repeat of GAAT that occurs 6 times:(GAAT), (GAAT), (GAAT), (GAAT), (GAAT), (GAAT).A different form of that STR could be four repeats in a different person: (GAAT), (GAAT), (GAAT), (GAAT)
why do forensic scientists use the 13 core STRs for identification?
Some chromosomes have more than 1 core STR locus, while others do not have any of the core STR loci. Some are easier to identify because of its number of repeats. It simplified a way of coding region of high variability.
What is an allele?
an alternative form of a gene
What happens when several core STR loci are used when comparing two DNA
profiles?
it provides greater probability of knowing that the DNA profile came from one individual and not someone else.
How are STR markers identified during STR analysis?
adding fluorescent dyes to the PCR reaction, it is possible to identify different STR markers
STR alleles are id by size and color on the graphic display
What is an allele frequency?
a calculation of how often a particular allele appears within
a given population.
Why are Y STRs unique?
only males carry a Y chromosome.
Why is mtDNA important for establishing familial connections?
Ancestry traced through the maternal line uses mtDNA because only mothers pass on mitochondrial DNA
Why do forensic scientists only look at the regions of high variability while
comparing two DNA profiles?
-low variability means that there’s little difference between 2 profiles
-99% of all human DNA is the same, so scientists only need to examine that 1% region of variability
How were forensic scientists able to confirm the remains of Saddam Hussein?
scientists compared samples of DNA from his sons.Saddam’s identity was confirmed using a rapid DNA test that compared his Y
STRs to his sons
Why does DNA profiling raise civil liberty concerns?
this is a violation of the Fourth Amendment right that
protects the individual from improper search and seizure.
Why did STR analysis replace gel electrophoresis?
has fewer bases that can retrieve degraded or limited samples of DNA.
What are the coding regions called and what are the noncoding regions called?
exon coding regions
introns non coding regions
What is NDIS?
-National DNA Index System (NDIS)
-Database of DNA profiles of individuals who were involved of a serious
crime.
What is CODIS?
-Combined DNA Index System (CODIS)
-Collects, analyzes, and communicates criminal information.
-NDIS is a part of CODIS
