DNA Evidence Notes
What did James Watson, Francis Crick, and Rosalind Franklin do?
-1953 -Discovered the shape of the DNA molecule
What is inclusion?
DNA bands match and the suspect is still a suspect
What does homozygous mean?
Having two identical genes
What do the order of the bases determine?
The genetic code
Each person's DNA is __________ from other people
Different (including identical twins, although they may not be able to be distinguished in a DNA test depending on which area is tested)
What are polymerases?
Enzymes that assemble new DNA strands when DNA is copying itself
What is locus (plural loci)?
Exact location of the DNA molecule of a gene or area of interest
What does DNA contain?
Genetic information
What does heterozygous mean?
Having two different forms of the gene
DNA can __________ through DNA from relatives, even when no body can be found
Identify a victim
Where is DNA found?
In the chromosomes located in the nucleus of our cells
What did Alec Jeffreys do?
Isolated DNA markers and called them "DNA fingerprints"
DNA can __________ by linking the same perpetrator to different scenes locally, statewide, and across the nation
Link crime scenes together
What is the genetic code?
Sequence of letters on a DNA strand
What are the rungs in DNA made up of?
The rungs that form the middle of the molecule are made up of pairs of nucleotides, or nitrogen bases
What makes up DNA?
The sides, or backbone, of the DNA molecule are made up of sugar (deoxyribose) and phosphate groups
Adenine (A) pairs with...
Thymine (T)
What are genes?
Unit of heredity
The PCR technique is used when?
Used when you have a small amount of DNA and need to make many copies for testing
What can DNA not show?
When the suspect was at the crime scene or for how long
Each person's pattern of fragments is what?
Different
What did Kary Mullis do?
-1985 -Developed the PCR procedure
How is the RFLP method done?
-DNA is cut into pieces called restriction fragments by enzymes -The enzymes cut at specific DNA sequences (like AAG) -The enzymes cut in different places for different people -The DNA ends up as different length pieces which can be separated on a gel
What is CODIS?
-Electronic database of DNA profiles that can identify suspects -DNA profiles from individuals convicted of certain crimes such as rape, murder, and child abuse are entered into CODIS and help officers identify possible suspects
DNA can __________ and __________
-Refute a claim of self-defense -Put a weapon in the suspect's hand
What can environmental factors do to DNA?
-They can destroy DNA evidence (ex. heat, sunlight, moisture, bacteria, and mold) -Therefore, not all DNA evidence will result in a usable DNA profile
DNA collected from a crime scene can either __________ or __________ (Similar to the use of fingerprints)
1. Link a suspect to the evidence 2. Eliminate a suspect
2 DNA Typing Methods:
1. RFLP Method 2. PCR Technique
The RFLP method requires what?
A large amount of DNA
What is a human genome?
A project designed to determine the order of the bases on all 23 human chromosomes
What is a probe?
A single strand of nucleic acid that has been made so that its sequence lines up with a certain DNA sequence; can be labeled with radioactive material
What does CODIS stand for?
COmbined DNA Index System
Guanine (G) pairs with...
Cytosine (C)
What is exclusion?
DNA bands do not match and the person is no longer a suspect
How is the PCR technique done?
DNA is heated and cooled with enzymes to make copies of a desired fragment before RFLP testing can be performed
What does DNA stand for?
Deoxyribonucleic Acid
What is recombinant DNA?
Opening up the DNA helix and combining it with another strand
What are chromosomes?
Pieces of genetic material
DNA can do what to a suspect?
Place the individual at a crime scene, in a home, or in a room the suspect claimed not to have been
What does PCR stand for?
Polymerase Chain Reaction
What does RFLP stand for?
Restriction Fragment Length Polymorphism