Chapter 5: DNA

Allele

one of several possible variants of the genetic code at a specific location along the DNA molecule.

Annealing

the pairing of nucleotides in complementary DNA strands together by forming hydrogen bonds.

Base Pairing

when two nitrogen bases in complimentary strands connect to form a hydrogen bond, holding the two DNA strands together.

in DNA...

Adenine (A) pairs only with Thymine (T) and Guanine (G) pairs only with Cytosine (C)

Chromosome

The strand of DNA and its associated proteins found in the nucleus of a cell that carries its genetic information.

CODIS

Combined DNA Identification System, developed by the FBI to store DNA information in a searchable computer database.

Complimentary DNA

a strand of DNA in which the sequence of bases matches those of another strand of DNA according to pairing rules. Thus, if the original strand contains an "A" nucleotide at a particular location, the complementary strand would have a "T" nucleotide at the equivalent location.

Denaturation

The process of separating the two strands of DNA into individual strands.

DNA

deoxyribonucleic acid; the basic genetic molecule of living organisms composed of repeating three groups (nucleotides): a phosphate, a deoxyribose sugar, and a nitrogen base.

Enzyme

a protein that catalyzes a chemical reaction; affects the rate of a chemical reaction without being consumed by the reaction.

Extension

Completing a complementary DNA strand from a template strand.

Gel electrophoresis

the process of separating DNA fragments based upon their charge and size. Charged DNA fragments are placed in a gel bed and moved through the medium by applying an electric current. Shorter fragments move fastest and farthest through the gel while longer fragments move the least.

Gene

Region along the DNA strand that provides coding information for the synthesis of proteins.

Hybridization

the process of joining together complimentary strands of DNA through base-pairing.

Hypervariable DNA

(also called "junk", "non-coding" or "nonsense" DNA) a region of DNA that shows a great degree of variability in a population and do not code for any known protein but may have a role in as molecular switches and play crucial roles in regulating genes.

Locus (plural "loci")

a specific position on the DNA strand.

Mitochondrial DNA

mtDNA; a small circle of DNA that resides outside the nucleus in the cellular mitochondria. mtDNA is only inherited from mothers and passed to all offspring.

Mutation

an inheritable change in the base sequence of DNA.

Nucleotide

the basic building block of DNA, consisting of a phosphate, a deoxyribose sugar, and a nitrogen base.

PCR

polymerase chain reaction; laboratory method for the rapid replication of specific regions of DNA.

Population

a specific group of people defined by geography, race, of other defining features.

Restriction Enzyme

a protein that locates a specific DNA sequence and cuts the DNA strand at that location.

RFLP

restriction fragment length polymorphism. Introduction to Forensic Science Chapter 5 Page 44 Draft 12/3/20 J. T. Spencer

STR

short tandem repeat; a region of DNA in which a small sequence of nucleotides (2 to 6 nucleotides) is repeated multiple times.

VNTR

Variable number tandem repeat; a region of DNA in which a larger sequence of nucleotides (up to fifty nucleotides) is repeated multiple times.

Y Chromosome

the chromosome inherited only through the father and passed along only to male offspring.

1868

Miescher "discovers" DNA

1953

Watson and Crick report double helix structure

1977

First human gene cloned.

1985

Jeffreys reports VNTR DNA sequences

1985

First report of PCR method

1986

Jeffreys uses DNA to solve first murder case (Pitchfork case)

1987

First conviction on DNA evidence (Andrews case)

1991

STRs first reported

1998

FBI starts CODIS database

2005

2.5 million DNA "finger-prints" in FBI database

Gene

A short portion of DNA that codes for something

Chimerism

a person has two completely separate cell lines within their bodies, each with its own entirely different set of chromosomes.