DNA

A. Terminology A. Terminology Chromosomes- strands of genetic material Chromosomes- strands of genetic material Genes- Fundamental unit of heredity Genes- Fundamental unit of heredity Locus (loci)-Exact location on the DNA molecule of a gene or area of interest Locus (loci)-Exact location on the DNA molecule of a gene or area of interest Homozygous-Two identical gene pairs Homozygous-Two identical gene pairs Heterozygous-Two different forms of the gene Heterozygous-Two different forms of the gene Recombinant DNA-Opening up the base pairs of the helix and recombining it with another strand Recombinant DNA-Opening up the base pairs of the helix and recombining it with another strand

DNA fingerprints Genetic code-Sequence of letters on a DNA strand Genetic code-Sequence of letters on a DNA strand Restriction enzymes-Chemicals that cut DNA into fragments that can later be incorporated into another DNA strand; about 150 are commercially available Restriction enzymes-Chemicals that cut DNA into fragments that can later be incorporated into another DNA strand; about 150 are commercially available Probe- A single strand of nucleic acid, much like RNA, that has been made in a way that its base sequence lines up to hybridize areas in an allele; usually labeled with radioactive material Probe- A single strand of nucleic acid, much like RNA, that has been made in a way that its base sequence lines up to hybridize areas in an allele; usually labeled with radioactive material

Human gene- A project designed to determine the order of bases on all 23 pairs of human chromosomes Human gene- A project designed to determine the order of bases on all 23 pairs of human chromosomes B. History B. History 1. James Watson and Francis Crick discovered the configuration of the DNA molecule 1. James Watson and Francis Crick discovered the configuration of the DNA molecule Alec Jeffreys- Isolated DNA markers& called them DNA fingerprints Alec Jeffreys- Isolated DNA markers& called them DNA fingerprints

Kary Mullis developed PCR testing Kary Mullis developed PCR testing C. Structure C. Structure Polymer- A very large molecule made by linking together a series of repeating units Polymer- A very large molecule made by linking together a series of repeating units Nucleotides- A unit composed of a sugar molecule, a phosphorous group and a nitrogen-containing base Nucleotides- A unit composed of a sugar molecule, a phosphorous group and a nitrogen-containing base Bases-Adenine, cytosine, guanine, & thymine Bases-Adenine, cytosine, guanine, & thymine

Double Helix- Two coiled DNA strands Double Helix- Two coiled DNA strands Base Pairing- A to T and G to C Base Pairing- A to T and G to C Proteins- Made by linking togerther a combination amino acids from a combination of up to 20 unknown Proteins- Made by linking togerther a combination amino acids from a combination of up to 20 unknown Amino acid codes- building blocks of protein are coded by a sequence of three bases. Amino acid codes- building blocks of protein are coded by a sequence of three bases.

D. Replication D. Replication 1. process- unwinding the DNA strands in the double helix; exposing the strand to a collection of free nucleotides; letter by letter the double helix is recreated in the proper order 2. Polymerases- enzymes that assemble a new DNA strand in the proper base sequence determined by the original or parent DNA strand

E. DNA Typing E. DNA Typing 1. RFLP- restriction fragment length polymorphisms; requires high molcular weight DNA 1. RFLP- restriction fragment length polymorphisms; requires high molcular weight DNA Visual evaluation- soak and free up the DNA Visual evaluation- soak and free up the DNA Assay- electrophoresis Assay- electrophoresis Digestion- by the restriction enzyme Digestion- by the restriction enzyme

Test gel Test gel Prepare known samples Prepare known samples Electrophoresis of all samples Electrophoresis of all samples Southern blotting- transfer the fragments to a nylon membrane Southern blotting- transfer the fragments to a nylon membrane Hybridization- nylon treated with radioactive probes containing a base sequence complementary to the RFLPs being identified Hybridization- nylon treated with radioactive probes containing a base sequence complementary to the RFLPs being identified

Autoradiography- nylon sheet is placed against X-ray film and exposed for several days Autoradiography- nylon sheet is placed against X-ray film and exposed for several days Additional probes- adding more probes increases probability of having a match Additional probes- adding more probes increases probability of having a match 2. PCR- polymerase chain reaction; need only low molecular weight DNA 2. PCR- polymerase chain reaction; need only low molecular weight DNA

DNA is denatured by heating it to 95 degrees Celsius, splitting the bonds between the two halves DNA is denatured by heating it to 95 degrees Celsius, splitting the bonds between the two halves Heat is reduced and DNA primer are added which hybridizes to site-specific arrangements of complementary bases Heat is reduced and DNA primer are added which hybridizes to site-specific arrangements of complementary bases A DNA polymerase is added that replicate the DNA; the primer attracts them to the open bases and they pair up until the clone is complete A DNA polymerase is added that replicate the DNA; the primer attracts them to the open bases and they pair up until the clone is complete

STEP c is repeated over and over STEP c is repeated over and over 3. match 3. match Inclusion- DNA bands match and the suspect is still a suspect Inclusion- DNA bands match and the suspect is still a suspect Exclusion- DNA bands don’t match and the person is no longer a suspect Exclusion- DNA bands don’t match and the person is no longer a suspect F. Present and the Future F. Present and the Future

CODIS- Computer Based DNA Information System; a data base of DNA profiles of individuals convicted of sex crimes and other violent crimes CODIS- Computer Based DNA Information System; a data base of DNA profiles of individuals convicted of sex crimes and other violent crimes TWGDAM- The Working Group for DNA Analytical Methods wrote the standards for DNA analysis that are part of a national crime laboratory accreditation program TWGDAM- The Working Group for DNA Analytical Methods wrote the standards for DNA analysis that are part of a national crime laboratory accreditation program