DNA DNA

A. TerminologyA. TerminologyChromosomes- strands of genetic materialChromosomes- strands of genetic materialGenes- Fundamental unit of heredityGenes- Fundamental unit of heredityLocus (loci)-Exact location on the DNA Locus (loci)-Exact location on the DNA

molecule of a gene or area of interestmolecule of a gene or area of interestHomozygous-Two identical gene pairsHomozygous-Two identical gene pairsHeterozygous-Two different forms of the geneHeterozygous-Two different forms of the geneRecombinant DNA-Opening up the base pairs Recombinant DNA-Opening up the base pairs

of the helix and recombining it with another of the helix and recombining it with another strandstrand

DNA fingerprintsDNA fingerprints

Genetic code-Sequence of letters on a DNA Genetic code-Sequence of letters on a DNA strandstrand

Restriction enzymes-Chemicals that cut DNA Restriction enzymes-Chemicals that cut DNA into fragments that can later be incorporated into into fragments that can later be incorporated into another DNA strand; about 150 are another DNA strand; about 150 are commercially availablecommercially available

Probe- A single strand of nucleic acid, much like Probe- A single strand of nucleic acid, much like RNA, that has been made in a way that its base RNA, that has been made in a way that its base sequence lines up to hybridize areas in an allele; sequence lines up to hybridize areas in an allele; usually labeled with radioactive materialusually labeled with radioactive material

Human gene- A project designed to Human gene- A project designed to determine the order of bases on all 23 determine the order of bases on all 23 pairs of human chromosomespairs of human chromosomes

B. HistoryB. History1. James Watson and Francis Crick- 1953 1. James Watson and Francis Crick- 1953

discovered the configuration of the DNA discovered the configuration of the DNA moleculemoleculeAlec Jeffreys- Isolated DNA markers& called Alec Jeffreys- Isolated DNA markers& called

them DNA fingerprintsthem DNA fingerprints

Kary Mullis- 1985 developed PCR testingKary Mullis- 1985 developed PCR testing

C. StructureC. StructurePolymer- A very large molecule made by Polymer- A very large molecule made by

linking together a series of repeating unitslinking together a series of repeating unitsNucleotides- A unit composed of a sugar Nucleotides- A unit composed of a sugar

molecule, a phosphorous group and a molecule, a phosphorous group and a nitrogen-containing basenitrogen-containing base

Bases-Adenine, cytosine, guanine, & thymineBases-Adenine, cytosine, guanine, & thymine

Double Helix- Two coiled DNA strandsDouble Helix- Two coiled DNA strandsBase Pairing- A to T and G to CBase Pairing- A to T and G to CProteins- Made by linking togerther a Proteins- Made by linking togerther a

combination amino acids from a combination amino acids from a combination of up to 20 unknowncombination of up to 20 unknown

Amino acid codes- building blocks of Amino acid codes- building blocks of protein are coded by a sequence of three protein are coded by a sequence of three bases.bases.

D. ReplicationD. Replication1.1. process- unwinding the DNA strands in the process- unwinding the DNA strands in the

double helix; exposing the strand to a double helix; exposing the strand to a collection of free nucleotides; letter by letter collection of free nucleotides; letter by letter the double helix is recreated in the proper the double helix is recreated in the proper orderorder

2.2. Polymerases- enzymes that assemble a Polymerases- enzymes that assemble a new DNA strand in the proper base new DNA strand in the proper base sequence determined by the original or sequence determined by the original or parent DNA strandparent DNA strand

E. DNA TypingE. DNA Typing1. RFLP- restriction fragment length 1. RFLP- restriction fragment length

polymorphisms; requires high molcular polymorphisms; requires high molcular weight DNAweight DNA

Visual evaluation- soak and free up the Visual evaluation- soak and free up the DNADNA

Assay- electrophoresisAssay- electrophoresisDigestion- by the restriction enzymeDigestion- by the restriction enzyme

Test gelTest gelPrepare known samplesPrepare known samplesElectrophoresis of all samplesElectrophoresis of all samplesSouthern blotting- transfer the fragments Southern blotting- transfer the fragments

to a nylon membraneto a nylon membraneHybridization- nylon treated with Hybridization- nylon treated with

radioactive probes containing a base radioactive probes containing a base sequence complementary to the RFLPs sequence complementary to the RFLPs being identifiedbeing identified

Autoradiography- nylon sheet is placed Autoradiography- nylon sheet is placed against X-ray film and exposed for several against X-ray film and exposed for several daysdays

Additional probes- adding more probes Additional probes- adding more probes increases probability of having a matchincreases probability of having a match

2. PCR- polymerase chain reaction; need 2. PCR- polymerase chain reaction; need only low molecular weight DNAonly low molecular weight DNA

DNA is denatured by heating it to 95 degrees DNA is denatured by heating it to 95 degrees Celsius, splitting the bonds between the two Celsius, splitting the bonds between the two halveshalves

Heat is reduced and DNA primer are added Heat is reduced and DNA primer are added which hybridizes to site-specific arrangements of which hybridizes to site-specific arrangements of complementary basescomplementary bases

A DNA polymerase is added that replicate the A DNA polymerase is added that replicate the DNA; the primer attracts them to the open bases DNA; the primer attracts them to the open bases and they pair up until the clone is completeand they pair up until the clone is complete

STEP c is repeated over and overSTEP c is repeated over and over3. match3. match Inclusion- DNA bands match and the Inclusion- DNA bands match and the

suspect is still a suspectsuspect is still a suspectExclusion- DNA bands don’t match and Exclusion- DNA bands don’t match and

the person is no longer a suspectthe person is no longer a suspectF. Present and the FutureF. Present and the Future

CODIS- Computer Based DNA Information CODIS- Computer Based DNA Information System; a data base of DNA profiles of System; a data base of DNA profiles of individuals convicted of sex crimes and individuals convicted of sex crimes and other violent crimesother violent crimes

TWGDAM- The Working Group for DNA TWGDAM- The Working Group for DNA Analytical Methods wrote the standards for Analytical Methods wrote the standards for DNA analysis that are part of a national DNA analysis that are part of a national crime laboratory accreditation programcrime laboratory accreditation program