DNA and GenesDNA and GenesModified Chapters 10, 11, & 12

DNA verse RNA….ReviewDNA verse RNA….ReviewDNA and RNA are nucleic acids

◦DNA – genetic information◦RNA – used to build proteins

Built by nucleotidesCan be single stranded or double

strandedBasesBonds

DNA ReplicationDNA ReplicationComplete 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:Overview:

1. Strands separate a. New nucleotides b. Result: 2 DNA copies, each:

1 new & 1 old chain2. DNA polymerase3. Leading strand4. Lagging strand5. Primer

Flow of Genetic Information Flow of Genetic Information from DNA to RNA to Proteinfrom 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 Flow of Genetic Information from DNA to RNA to ProteinDNA 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: TranscriptionTranscription

◦ Occurs in nucleusOccurs in nucleus◦ Genetic information

transferred from DNA to RNA

◦ Important players: RNA polymerase Ribosomal RNA (rRNA)

◦ Introns removed◦ Exons spliced together

TranslationTranslation

Occurs in cytoplasmConversion 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 The genetic code (RNA codons)codons)

There are 64 different codons in the genetic code!!!!

Genes gone bad…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 REGULATIONGENE REGULATION

How are Genes How are Genes Regulated??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

BacteriaBacteriaControl sequences

◦ Stretches of DNA that coordinate gene expression

An operon◦ Cluster of genes with related functions,

including the control sequencesA promoter

◦ Control sequence◦ Site where the transcription enzyme initiates

transcriptionAn operator

◦ DNA sequence between the promoter and the enzyme genes

◦ Acts as an on and off switch for the genes

DNA TECHNOLOGYDNA TECHNOLOGY

Cloning Plants and Cloning Plants and AnimalsAnimalsRegeneration

◦ Regrowth of lost body parts in animalsNuclear 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 Recombinant DNA TechnologyTechnology

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) Genetically Modified (GM) FoodsFoods

Replacing traditional plant-breeding programs

Corn has been genetically modified to resist insect infestation

Recombinant DNA Recombinant DNA TechniquesTechniques

Bacteria….To work with

genes in the laboratory, biologists often use bacterial plasmids◦ Small, circular DNA

molecules

Recombinant DNA Recombinant DNA TechniquesTechniques

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 Cutting and Pasting DNA with Restriction EnzymesEnzymes

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 Transformation of Insulin GeneGene 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 FingerprintingDNA Fingerprinting and Forensic and Forensic ScienceScience

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 TESTINGGENETIC TESTING

The Polymerase Chain Reaction The Polymerase Chain Reaction (PCR)(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 ElectrophoresisGel 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

CASESCASES

The Human Genome The Human Genome ProjectProject•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 3164.7 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 http://www.ornl.gov/hgmis/project/info.html#how

•Proposed 1990; 15-year time frame

Some Goals of the Human Some Goals of the Human Genome ProjectGenome 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 Ethical Issues of Human Genome ProjectGenome 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 KillerTracking 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 anthraxInvestigators 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 TherapyHuman 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…”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

http://www.imdb.com/video/imdb/vi4273341977/