Cutting and Pasting DNA The cutters are called restriction enzymes, they cut DNA at specific nucleotide sequences

Restriction enzyme cuts DNA into fragments Addition of a DNA fragment from another source Fragments stick together by base pairing DNA ligase joins the strands Recognition sequence for a restriction enzyme Sticky end Recombinant DNA molecule

How Do I Obtain the Gene of Interest? The “shotgun” approach - millions of recombinant plasmids are produced; a genomic library

How a DNA probe tags a gene Radioactive probe (DNA) Single-stranded DNA Mix with single-stranded DNA from various bacterial clones Base pairing indicates the gene of interest

The reverse transcriptase method Transcription Introns removed and exons spliced together Isolation of mRNA from cell and addition of reverse transcriptase 5 Synthesis of second DNA strand Synthesis of cDNA strand ExonIntronExonIntronExon Cell nucleus DNA of eukaryotic gene RNA transcript mRNA Cytoplasm Reverse transcriptase Test tube cDNA strand being synthesized cDNA of gene with- out introns

DNA technology revolutionized forensics WHO ARE YOU? –forensics is the scientific analysis of evidence from crime scene investigations

DNA fingerprinting has been available since 1986DNA fingerprinting Used in CSI, victim IDs; Cheddar Man Crimes and Other Investigations

Polymerase Chain Reaction (PCR) copies DNA DNA Fingerprinting Techniques - PCR

DNA amplification by PCR Tiny amount of DNA 8421 Number of DNA molecules

DNA fragments cut by restriction enzymes are seen as “bands” in an electrophoresis gel Longer fragments Shorter fragments Crime scene DNA Suspect DNA

Defendant’s blood Blood on defendant’s clothes Victim’s blood

The science of studying entire genomes GENOMICS

In 1990, an international consortium began the Human Genome Project The Human Genome Project –sequencing the human genomesequencing –challenges: large size, and the fact that only a small amount of our DNA is genetic

Genome mapping Chop up with restriction enzyme Chromosome Sequence fragments DNA fragments Align fragments Reassemble full sequence

Gene therapy cures disease by altering human genes HUMAN GENE THERAPY

Normal human gene isolated and cloned Human gene inserted into virus Virus injected into patient Healthy individual Nonharmful virus (vector) Virus containing normal human gene Bone marrow

Great power brings both promise and danger SAFETY AND ETHICAL ISSUES –strict laboratory safety procedures are used –negotiators from 130 countries agreed on a Biosafety Protocol for GM foods