DNA and Genes Modified Chapters 10, 11, & 12

DNA verse RNA….Review DNA and RNA are nucleic acids ◦ DNA – genetic information ◦ RNA – used to build proteins Built by nucleotides Can be single stranded or double stranded Bases Bonds

DNA Replication Complete set of genetic instructions must pass from one generation to the next Begins at specific sites on a double helix Proceeds in both directions

Overview: 1. Strands separate a. New nucleotides b. Result: 2 DNA copies, each: 1 new & 1 old chain 2. DNA polymerase 3. Leading strand 4. Lagging strand 5. Primer

Flow of Genetic Information from DNA to RNA to Protein Information contained in DNA is stored in blocks called genes ◦ genes code for proteins ◦ proteins determine what a cell will be like DNA stores information in nucleus ◦ instructions are copied from the DNA into messages comprised of RNA ◦ these messages are sent out into the cell  direct the assembly of proteins

Flow of Genetic Information from DNA to RNA to Protein The path of information is often referred to as the central dogma DNA  RNA  protein Gene expression : ◦ Transcription  messenger RNA (mRNA) made from a gene within the DNA ◦ Translation  Using the mRNA to direct the production of a protein

Transcription: Transcription Transcription ◦ Occurs in nucleus ◦ Genetic information transferred from DNA to RNA ◦ Important players:  RNA polymerase  Ribosomal RNA (rRNA) ◦ Introns removed ◦ Exons spliced together

Translation Occurs in cytoplasm Conversion from the nucleic acid language to the protein language Important players: ◦ Messenger RNA (mRNA)  mRNA is “read” in three- nucleotide units called codons ◦ Transfer RNA (tRNA)

The genetic code (RNA codons) There are 64 different codons in the genetic code!!!!

Genes gone bad… Mutation ◦ Any change in the nucleotide sequence of DNA ◦ Can result in changes in the amino acids in proteins ◦ Often harmful, but are they always?? Mutations may result from ◦ Errors in DNA replication ◦ Physical or chemical agents called mutagens

GENE REGULATION

How are Genes Regulated?? In cellular differentiation: ◦ Certain genes turned on and off ◦ Cells become specialized in structure and function In gene expression: ◦ A gene is turned on and transcribed into RNA ◦ Information flows from genes to proteins, genotype to phenotype

Bacteria Control sequences ◦ Stretches of DNA that coordinate gene expression An operon ◦ Cluster of genes with related functions, including the control sequences A promoter ◦ Control sequence ◦ Site where the transcription enzyme initiates transcription An operator ◦ DNA sequence between the promoter and the enzyme genes ◦ Acts as an on and off switch for the genes

DNA TECHNOLOGY

Cloning Plants and Animals Regeneration ◦ Regrowth of lost body parts in animals Nuclear transplantation ◦ Involves replacing nuclei of egg cells with nuclei from differentiated cells ◦ Has been used to clone a variety of animals Scottish researchers cloned the first mammal in 1997 ◦ Dolly!! ◦ Reproductive cloning

Recombinant DNA Technology Set of techniques for combining genes from different sources into a single DNA molecule genetically modified (GM) organism ◦ organism that carries recombinant DNA Recombinant DNA technology is applied in the field of biotechnology ◦ Biotechnology uses various organisms to perform practical tasks

Genetically Modified (GM) Foods Replacing traditional plant-breeding programs Corn has been genetically modified to resist insect infestation

Recombinant DNA Techniques Bacteria…. To work with genes in the laboratory, biologists often use bacterial plasmids ◦ Small, circular DNA molecules

Recombinant DNA Techniques Plasmids ◦ Can easily incorporate foreign DNA ◦ Readily taken up by bacterial cells ◦ Act as vectors  DNA carriers that move genes from one cell to another Can help biologists produce large quantities of a desired protein

Cutting and Pasting DNA with Restriction Enzymes To combine the plasmid and gene: ◦ piece of DNA must be spliced into a plasmid  Accomplished using restriction enzymes  cut DNA at specific nucleotide sequences  cuts produce pieces of DNA called restriction fragments  May have “sticky ends” that are important for joining DNA from different sources

Transformation of Insulin Gene human insulin gene isolated and cut from its location on the human chromosome ◦ using a restriction enzyme plasmid is cut using the same restriction enzyme desired DNA (insulin gene) and plasmid DNA can be joined using DNA ligase plasmid now contains the genetic instructions on how to produce the protein insulin Bacteria can be artificially induced to take up the recombinant DNA plasmids and be transformed ◦ successfully transformed bacteria will contain the desired insulin gene transformed bacteria containing the insulin gene can be isolated and grown As transformed bacteria grow they will produce the insulin proteins coded for the recombinant DNA ◦ Insulin harvested and used to treat diabetes

DNA Fingerprinting and Forensic Science DNA technology has rapidly revolutionized the field of forensics ◦ scientific analysis of evidence from crime scenes Uses: ◦ Paternity ◦ Victim identification ◦ Crimes ◦ Evolutionary research  Study ancient pieces of DNA  Cheddar Man!!!!

GENETIC TESTING

The Polymerase Chain Reaction (PCR) Technique by which any segment of DNA can be copied quickly and precisely ◦ Scientists can obtain enough DNA from even minute amounts of blood or other tissue to allow DNA fingerprinting

Gel Electrophoresis Used to separate the DNA fragments obtained from different sources The DNA fragments are visualized as “bands” on the gel ◦ The bands of different DNA samples can then be compared

CASES

The Human Genome Project Joint project of National Institute of Health (NIH) and Department of Energy (DOE) Now an international effort What is DNA sequencing? process of determining the exact order of the million chemical nucleotide bases that make up the DNA of the 24 different human chromosomes How do they do it? For details on the procedure, check out w Proposed 1990; 15-year time frame

Some Goals of the Human Genome Project identify all the approximately 30,000 genes in human DNA determine the sequences of the 3 billion chemical base pairs that make up human DNA store this information in databases improve tools for data analysis transfer related technologies to the private sector

Ethical Issues of Human Genome Project Privacy of Genetic Information: Who gets to know? Mates/spouses Insurance companies Employers Testing for Diseases: Do you want to know? What now? Prenatal testing Diseases with no cure/treatment

Tracking the Anthrax Killer In October 2001, Florida man died from inhalation anthrax ◦ By the end of the year, four other people had also died from anthrax Investigators analyzed the genome of the anthrax spores used in each attack ◦ Able to establish that the spores from all of the cases were identical  Suggested a single perpetrator of the crime  Able to match the anthrax with one laboratory subtype  The Ames strain

Human Gene Therapy recombinant DNA procedure that seeks to treat disease by altering the genes of the afflicted person ◦ The mutant version of a gene is replaced or supplemented with a properly functioning one

“Conviction…” Betty Anne Waters ◦ Ayer, MA 1982 – brother arrested for murder Waters went to CCRI ◦ GED ◦ Associates ◦ Went to Roger Williams to get Bachelors and Law degree Became brothers lawyer ◦ Witnesses lied**** ◦ DNA evidence in 1990’s ◦ Innocence Project Released in 2001 after serving 18 years in prison ◦ $3.4 million dollar settlement