Chapter 11 DNA and the Language of Life

Chapter 11 DNA and the Language of Life 11.1 Genes are made of DNA Griffith was trying to find a vaccine for Streptococcus pneumoniae. Worked with two types or strains. Capsule composed of polysaccharides so called smooth- edged (S). No capsule so called rough-edged (R).Griffith knew that mice infected with S bacteria grew sick and died, while mice infected with R bacteria were not harmed.

Somehow the harmless R bacteria had changed into virulent S bacteria.

Transformation: Is a change in genotype caused when cells take up foreign genetic material.

Scientist were trying to figure out if genes are made of DNA or protein. Proteins has 20 different amino acid blocksDNA has 4 different nucleotide blocks. Averys ExperimentUsed proteindestroying enzymes to destroy protein. Transformation occurred.

Used DNA-destroying enzymes to destroy DNA. Transformation did not occur.

Avery discovered that DNA is the material responsible for transformation and that the genetic material is composed of DNA. Hershey-Chase ExperimentVirus: A package of nucleic acid wrapped in a protein coat. Viruses are not living, and can only reproduce with a host.

Bacteriophage: A virus that infects bacteria.

Hershey-Chase ExperimentT2 phages were labeled with radioactive isotopes. Viruss protein coat with sulfur 35S and Viruss DNA core with phosphorus 32P.

The phages were used to infect two separate E. coli bacterial cells.

32P moved into cells. DNA must carry genetic information.

11.2 Nucleic Acids store information DNA = Deoxyribonucleic acid:Molecule where heritable genetic information of an organism is stored.

DNA is a nucleic acid, a polymer built from many monomers called nucleotides.Double strandedSugar= deoxyriboseBases=A-T-C-G

Nucleotide: Building blocks (the monomers) of nucleic acid polymers.

Structure:1. Ring-shaped sugar called deoxyribose2. Phosphate group 3. A nitrogenous baseAdenine AGuanine GThymine TCytosine C

Pyrimidines: Single ring structures such as T and CPurines: Double ring structures such as A and GDNA-Twisted ladderThe two sides of the ladder are made of alternating sugar parts and phosphate parts. (backbone)The rungs of the ladder are made of a pair of bases.

Wilkins and FranklinWilkins and Franklin developed X-ray diffraction photographs on DNA. (a beam of X-rays is directed at an object. The X-rays bounce off the object and are scattered in a pattern on a piece of film.)

Watson and CrickUsed Franklin and Wilsons X-ray diffraction research. Found the three-dimensional structure called the double helix. Built a DNA model configured in a double helix twisted ladder of two strands of nucleotides.

DNA Model

Discovering DNAs StructureChargoff discovered the amount of adenine always equaled the amount of thymine A=T, same for guanine and cytosine G=C.

Base Pairing RulesAdenine always pairs with Thymine.Cytosine always pairs with Guanine. Held together by H bonds.

Complimentary base pairs: Sequence of bases on one strand is paired to the sequence of bases on another strand.1A. TCGAACT1B. AGCTTGA

11.3 DNA replication is the molecular mechanism of inheritance When is the DNA copied?Before a cell can divide, its DNA must be copied.

HOW is the DNA copied?DNA replication - process of making a copy of DNA.

The Replication of DNAStep 1: DNA helicase opens the double helix by breaking the hydrogen bonds. Area where double helix separates is called the replication fork.

Step 2: DNA polymerase add nucleotides to the exposed nitrogen bases. Step 3: Process continues until all DNA has been copied, DNA polymerase detaches. Identical DNA strands.

Checking for ErrorsDNA polymerase proofreads while making new DNA. It can only add new nucleotides if the previous pair is correct.

Replication Video

11.4 A gene provides the information for making a specific protein RNA= Ribonucleic acid:A nucleic acid whose sugar is ribose rather than the deoxyribose of DNA. Single-stranded chain of nucleotidesNucleotide structurePhosphate group5-carbon sugar riboseNitrogenous basesAdenine (A) - Uracil (U)Guanine (G) - Cytosine (C)

RNA vs DNARNADNASugarRiboseDeoxyriboseStrandsSingleDoubleBasesA,U,C,GA,T,C,G

Protein Synthesis/Central Dogma Transcription: Process by which a DNA template is used to produce a single-stranded RNA molecule.

Translation: Process by which a sequence of nucleic acids in RNA is used to produce amino acids.

The flow of information from gene to protein is based on codons.Codon: On mRNAA three-base word that codes for one amino acid. RNA = AUCGGAUCGAUC GGA UCG

Codon Triplet CodeUsing RNA to amino acids

Lets Try DNA strand T A C G G C A T G A T C

mRNA strand

Start STOP 11.5 Two main steps from gene to protein Information Flow: DNA RNA Protein

During transcription, a sequence of nucleotides in DNA (a gene) is transcribed into RNA in the cell's nucleus.

During translation, the RNA travels to the cytoplasm where it is translated into the specific amino acid sequence of a protein.

TranscriptionTranslation

The Role of RNASeveral RNA molecules play a part in the steps from gene to protein:messenger RNA (mRNA) RNA molecule transcribed from a DNA template; carries the DNA instructions for making proteins to ribosomesribosomal RNA (rRNA) RNA that makes up ribosomestransfer RNA (tRNA) RNA that translates the three-letter codons of mRNA to amino acidsTRANSCRIPTION:DNA RNATranscription a sequence of nucleotides in DNA (a gene) is used to make an RNA copy of a gene1. DNA molecule unwinds2. RNA polymerase (enzyme) binds to the DNA and uses the DNA code to make a molecule of mRNA using complementary base pairing rules

Transcription DNA RNADNA strand T A C G G C A T G A T C

mRNA strand__________________________

http://www.youtube.com/watch?v=WsofH466lqk

TRANSLATION:RNA PROTEINWhat are the rules for translating the RNA sequence into an amino acid sequence? The mRNA molecule is translated three nucleotides, or a codon, at a time. Each codon codes for a particular amino acid in the final protein. START CODON (AUG) - codes for the amino acid methionine (Met) and also tells the ribosome where to start translation STOP CODONS do NOT code for amino acids, but tell the ribosome when to stop translationRole of the tRNA during TranslationtRNA: molecules transport and match amino acids to their appropriate codons on the mRNA transcript.

HOW?Each tRNA has a matching anticodon that is complementary mRNA codon.

TRANSLATION:RNA PROTEINSteps of Translation Newly transcribed RNA leaves the nucleus and enters the cytoplasmmRNA binds to a ribosome (rRNA) and translation begins with the START codontRNA carries amino acids to the ribosomeTranslation continues until a STOP codon is reachedThe newly made protein is released from the ribosome

Transcription DNA mRNADNA strandT A C G G C A T G A T CmRNA strandStart STOP Codon Codon Codon CodonAmino acidcarried by tRNA Polypeptide

Translation Video http://www.youtube.com/watch?v=5bLEDd-PSTQ

What process is this called?

DNA replication

What strand is the codon on?

A. rRNAB. mRNAC. tRNAD. DNA

What strand is the anti codon on?

A. rRNAB. mRNAC. tRNAD. DNA

11.6 Mutations can change the meaning of genes

Mutation:Any change in nucleotide sequence of DNA.

Mutagens:Physical or chemical agents that cause mutations. Ex. X ray or ultraviolet radiation.

Types of MutationsBase substitution replacement of one base or nucleotide with another

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Types of MutationsInsertion insertion of one or more nucleotides in a geneDeletion deletion of one or more nucleotides in a gene

Insertions and deletions are usually more disastrous than the effects of a base substitution because adding or subtracting nucleotides may alter the codons of the genetic message.

Mutations can changes appearance