forensics exam 3

What is the definition of DNA profiling

DNA profiling in a technique used by scientists to distinguish between individuals of the same species using only samples of their DNA

What is Stage 1 of DNA profiling

In stage one, cells are broken down to release DNA. If only a small amount of DNA is available, it can be amplified with PCR

What is the function of restriction enzymes

restruction enzymes cut DNA at specific base sites to break strands into smaller fragments

What base sequence does restriction enzyme EcoRI recognize

The base sequence GAATTC

What base sequence does restriction enzyme BAM Hi recognize

The base sequence GGATCC

What is the section of DNA that is cut out referred to

Restriction fragments

What is stage 3 of DNA profilng

restriction fragments are injected into gel wells

what is stage four of DNA profiling

restriction fragments are separated based on size

What biological materials can be used for DNA profiling

Blood

Hair

Semen

Saliva

Body tissue

Vaginal cells

What are the chances of two people having the same DNA profile

30,000 million to one

If the DNA profile matches the suspect, can it be used as evidene that they committed the crime

Without supporting evidence,a DNA profile match can only prove a suspect wat AT the crime scene not that they committed the crime

who was the first criminal caught based on DNA fingerprintng evidence

Colin Pitchfork

How many bases do most restriction enzymes cut

4-6 bases

what are restriction enzymes

restriction enzymes are endonucleases which catalyze the cleavage of phosphodiester bonds within both DNA strands

how many loci are comapred between a suspect and evidence DNA obtained from the crime scene

13 different loci

In what two ways can human DNA differ

1. Human DNA can differ from each other by single nucleotides. SNPS

2. Human DNA can differ from each other by Simple (intron) Sequence Repeats (SSRs)

Why is SNP analysis rarely used in forensic cases

Single Nucleotide Polymorphs are incredibly common within a population. If SNPs were to be used to identify an individual, dozens of SNPs would need to be examined to derive a true DNA fingerprint

What specialized applications can SNP analysis be used for

1. mitochondrial (maternal) DNA testing

2. Y (male) SNP as lineage markers or to identfy males in SA cases

3. Ancestry informative markers

4. The prediction of phenotypic traits, such as hair or eye color

What is STR (SSR) analysis

STR analysis is the most common type of DNA profiling used today. It relies on the analysis of short tandem repeat sequences (intron sequences) that will repeat a variable number of times in different individuals.

What three techniques are used in DNA fingerprinting analysis

1. Agarose Gel Electrophoresis of DNA samples

2. PCR of the target DNA from a crime scene

3. Sequencing of DNA to determine the nucleotide sequences in a sample following PCR

What can be used to aid in visualziing DNA fragments separated by gel electrophoresis

1. Ethidium Bromide and UV light

2. FlashBlue

Define RFLPs and give their significance

Restriction fragmnent length polymorphs are differences among people in their DNA sequences at sites recognized by restriction enzymes. This variation results in different sized (length) DNA fragments produced by restriction enzymes

What are variable number tandem repeats

VNTRs reffer to the variation in nucleotide sequence length within intron sequences

What individuals possess the same DNA fingerprints

Identical twins

List the steps involved in DNA fingerprinting

1. Obtain CS, suspect, and victum samples

2. dentarue cells and remove DNA

3. add restriction enzymes

4. incubate

5. add dye

6. run gel

7. interperate results

What type of cells can be used for DNA analysis

Any human cells contanting DNA:

Wbc

hair follicles

semen

vaginal cells

skin tissue

After conducting a standard gel using STR analysis, how could you further identify the parentage of three newborns who were mixed up?

One could use SNP analysis to identify the maternal inheritance of mitochondrial DNA. This would be a definitive way to identify the maternal parientage of a child, as mtDNA is always passed to children unchanged (not counting de novo mutations)