Forensic Science - DNA chapter 7

What does DNA stand for?

Deoxyribonucleic Acid

Where is DNA found?

- 90% is found in
nucleus
of every cell
- 10% is found in
mitochondria
(MDNA)

Where does DNA found in the mitochondria come from?

- mother
- only maternal inheritance

What is the entire sequence of all the genetic information called?

- the genome (DNA library)

Animal Cell vs. Bacterial cell

1.
Eukaryotic Cells
(Animal)
- everything, but bacteria --> animals, plants, mushrooms, amoeba
- DNA is about 3-6 feet in length in one cell
2.
Prokaryotic Cell
- bacteria
- circular DNA
- no organelles

What is the monomer of nucleic acid called?

nucleotide

What are the 2 types of Nitrogenous Bases? Which has double rings and single ring?

1. Purines --> double rings
2. Pyrimidines --> Single ring

What are the two Purines?

1. Guanine (G)
2. Adenine (A)

What are the two Pyrimidines?

1. Thymine (T)
2. Cytosine (C)

How do the Nitrogenous Bases pair up?

- Pyrimidine--purine
1. T-A or A-T
2. C-G or G-C

What bonds hold the nitrogenous bases together? Where are these bonds located?

- Hydrogen bonds
- alone the "center" of the ladder --> between the nitrogenous bases

What bonds hold the monomer (nucleotide) together? Where are these bonds located?

- Phosphodiester bonds
- on the sides of the ladder --> holds the monomer together

What's DNA electrophoresis?

- the separation of DNA according to size using electricity
- smaller amounts of DNA will travel faster to positive terminal

What are Restriction Enzymes?

- "scissors"
- microscopic
- chops up DNA --> put chunks of DNA into something else

What are Restriction Enzymes also called?

Restriction Endonucleases

What are Plasmids?

- auxiliary pieces of DNA
- morphs DNA in bacteria
- extra DNA found in bacteria

What is a Restriction Map?

-map of "scissors

What is a Cleavage Site?

- the location where the restriction enzyme cuts the DNA strand

What is a Palindrome?

- word/sentence that reads the same forward and backward
- ex. dad, mom, cccggg/gggccc, madam, civic, level

What is a sticky end?

- stair step
- jagged

What is a blunt end?

- smooth

What is Ligase?

glue"
- enzyme that puts DNA together
- need to have complementary pairs

What's Pipetting?

- to measure/transfer a quantity of a liquid using a pipette

What is the charge at the black and red terminal in gel electrophoresis?

- black terminal --> negative
- red terminal --> positive

Why does the phosphate move towards one pole versus the other?

- Phosphate is attached to the sugar and has a negative charge
- the negative charge is attracted to the positive terminal so it drags the DNA with it to the positive terminal
- the smaller pieces of DNA will be easily dragged by the phosphate (so smaller

What does the size of the fragment have to do with moving through the agarose material?

- the smaller the fragment, the more it travels down the lane (moves up closer to the positive terminal)
- the larger fragments don't travel as far

Which travels the farthest, a small fragment or large fragment?

- small

What is the role of the SDS solution and ethanol in the extraction of the DNA from the strawberry?

1. SDS --> Salt detergent ethanol?
- breaks down the outer layer of membrane, fats, lipids
- exposes the DNA inside the cell
2. Ethanol
- precipitates the DNA out
- allows a solid DNA to be visible to the human eye

What's a Radioactive Probe?

- attaches to specific fragments of DNA
- provides a "new" pattern that can match

In reference to the DNA structure, What is viscosity and elasticity?

When extracted..
1. Viscosity --> DNA is very sticky and gel-like
- resistance to flow
2. Elasticity --> DNA can be stretched and then bounce back together

Allele

An alternative form of a gene.

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Combined DNA Index System (CODIS)

the FBI's computerized criminal DNA databases as well as the software used to run these databases; includes the National DNA Index System (NDIS)

DNA fingerprint (profile)

pattern of DNA fragments obtained by analyzing a person's unique sequences of noncoding DNA

Exon

expressed sequence of DNA; codes for a protein

Gene

A segment of DNA on a chromosome that codes for a specific trait

Intron

sequence of DNA that is not involved in coding for a protein

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

polymerase chain reaction

A method of producing thousands of copies of DNA segment using the enzyme DNA polymerase. It can be used in crime scene investigation to amplify minute amount of DNA evidence.

Polymorphism

region of repeating DNA within an intron that is highly variable from person to person

primer

sequence of DNA added in a PCR to trigger replication of a specific section of DNA

restriction enzymes

molecular scissors; a molecule that cuts a DNA molecule at a specific base sequence.

restriction fragments

A DNA segment that results from the cutting of DNA by a restriction enzyme, as in preparation for gel electrophoresis.

VNTR(variable number of tandem repeats)

tandem (next to each other) repeats of a short DNA sequence (9 to 80 base pairs) with varying numbers of repeats among individuals

STRs (short tandem repeats)

-short nucleotide
-sequences that are repeated in tandem,
- composed of different numbers of repeating units in
individuals and
- used in DNA profiling.

single nucleotide polymorphism (SNP)

most common DNA variations in Humans. It is a single base-pair site in a genome where nucleotide variation is found in at least 1% of the population.