DNA and the DNA and the Language of LifeLanguage of LifeChapter 11Chapter 11
How did scientists How did scientists learned that DNA is learned that DNA is the genetic material?the genetic material?
Genes are Made of DNAGenes are Made of DNA
Griffin’s experiment (1928)Griffin’s experiment (1928) Avery’s experiment (1944)Avery’s experiment (1944) Hershey and Chase experiment (1952)Hershey and Chase experiment (1952)
Griffith’s experiment - Griffith’s experiment - 19281928
Griffith showed that although a deadly Griffith showed that although a deadly strain of bacteria could be made strain of bacteria could be made harmless by heating it, some factor in harmless by heating it, some factor in that strain is still able to change other that strain is still able to change other harmless bacteria into deadly ones. He harmless bacteria into deadly ones. He called this the "transforming factor."called this the "transforming factor."
Avery’s experiment - Avery’s experiment - 19441944
Transforming factor - Protein or DNA?Transforming factor - Protein or DNA?
Avery and colleagues treated a mixture of Avery and colleagues treated a mixture of heat- treated deadly strain and harmless heat- treated deadly strain and harmless strain of bacteria with:strain of bacteria with:
Protein-destroying enzymeProtein-destroying enzyme DNA-destroying enzymeDNA-destroying enzyme
Hershey and Chase Hershey and Chase experiment -1952experiment -1952
The basic unit of the DNA molecule is The basic unit of the DNA molecule is called:called:
NUCLEOTIDENUCLEOTIDE
A NUCLEOTIDE has three parts:A NUCLEOTIDE has three parts: A ring-shaped sugar called A ring-shaped sugar called deoxyribosedeoxyribose A A phosphate groupphosphate group A A nitrogenous basenitrogenous base (single or double ring of (single or double ring of
carbon and nitrogen atoms) carbon and nitrogen atoms)
Nitrogenous BasesNitrogenous Bases
Nucleotide monomers join together by covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar-phosphate backbone.
The bases pair up (A-The bases pair up (A-T & G-C) forming T & G-C) forming the double helix first the double helix first described by described by Watson and CrickWatson and Crick
Watson, Crick and Watson, Crick and FranklinFranklin
Various ways to model DNA Various ways to model DNA structurestructure
•http://www.umass.edu/molvis/tutorials/dna/dnapairs.htm manipulate DNA
Why does DNA need to Why does DNA need to be replicated?be replicated?Growth – new cells - reproductionGrowth – new cells - reproduction
How does this process How does this process happens?happens?
Weak bonds Weak bonds Hydrogen bondsHydrogen bonds Comes apart Comes apart
easilyeasily Comes together Comes together
easilyeasily
Overview of DNA Overview of DNA replicationreplication
DNA separatesDNA separates Complementary Complementary
nucleotides are nucleotides are linked along linked along separated strandsseparated strands
initiateinitiate
Initiator protein Initiator protein guides guides unzipper unzipper protein protein (helicase) to (helicase) to correct position correct position on DNAon DNA
untwisteruntwister
Untwister Untwister (topoisomerase) (topoisomerase) unwinds the unwinds the DNA double DNA double helix in advance helix in advance of the unzipperof the unzipper
• Unzipper separates DNA strands, breaking weak bonds between the nucleotides
unzipunzip
assembleassemble
• Builders (polymerases) assemble new DNA strand by joining nucleotides to their matching complements on the exposed strands
straightnersstraightners
Straighteners Straighteners (single-strand (single-strand DNA binding DNA binding proteins) proteins) keep single keep single strand of strand of DNA from DNA from tanglingtangling
Phosphate provides Phosphate provides energyenergy
• Phosphate bond energy from the new nucleotides is used to make the new bonds
Leading vs. Lagging Leading vs. Lagging strandstrand
Leading (top) Leading (top) strand is built strand is built continuously as continuously as the builder the builder follows behind follows behind the unzipper, the unzipper, but the Lagging but the Lagging (lower) strand (lower) strand builds in the builds in the opposite opposite directiondirection
Lagging strandLagging strand
Lagging Lagging (lower) (lower) builder builder makes a makes a loop with the loop with the DNA strand DNA strand and builds in and builds in opposite opposite directiondirection
Lagging strandLagging strand
Built in small Built in small sections sections
Sections Sections linked by linked by enzyme ligase enzyme ligase
Repairs of DNARepairs of DNA
Erasers (Repair Erasers (Repair Nuclease): find Nuclease): find poorly matched poorly matched or damaged or damaged nucleotides and nucleotides and cut them outcut them out
Repairs of DNARepairs of DNA
Builders Builders (Polymerase): (Polymerase): fill gaps using fill gaps using other DNA other DNA strand as a strand as a guideguide
Repairs of DNARepairs of DNA
Stitchers Stitchers (Ligase): uses (Ligase): uses ATP to restore ATP to restore continuity of continuity of backbone of backbone of repaired strandrepaired strand
Big picture of DNA Big picture of DNA replicationreplication
Replication reviewReplication review
REPLICATION IN 3 STEPSREPLICATION IN 3 STEPS
Conection between DNA Conection between DNA and Proteinand Protein
DNA defines the genotype (genetic DNA defines the genotype (genetic makeup)makeup)
Proteins determine the phenotype Proteins determine the phenotype (specific trait)(specific trait)
Each gene codes for one protein Each gene codes for one protein (polypeptide)(polypeptide)
Life is orchestrated by Life is orchestrated by ProteinsProteinsProteinsProteins Combinations of 20 Combinations of 20
different amino acids different amino acids linked in long chainslinked in long chains
Function is determined Function is determined by amino acid by amino acid sequencesequence
Amino acid sequence Amino acid sequence is determined by DNA is determined by DNA sequencesequence
Used for enzymes, Used for enzymes, hair, muscles, cell partshair, muscles, cell parts
Amino Acids LinkedAmino Acids Linked
Amino Acids Link Amino Acids Link Together to Together to Form a Protein Form a Protein (Polypeptide)(Polypeptide)
DNA to Protein ConectionDNA to Protein Conection
Geneticists Beadle and Tatum studied Geneticists Beadle and Tatum studied mutant strain of orange moldmutant strain of orange mold
This strain was missing a necessary This strain was missing a necessary enzyme for mold to growenzyme for mold to grow
Each mutant strain was defective in a Each mutant strain was defective in a single genesingle gene
One gene-on enzyme hypothesisOne gene-on enzyme hypothesis More accurate – One gene one polypeptide More accurate – One gene one polypeptide
Protein SynthesisProtein Synthesis
DNA → RNA → Protein (polypeptide)DNA → RNA → Protein (polypeptide)
This happens in two main steps:This happens in two main steps:
Transcription Transcription TranslationTranslation
Information is sent from the Information is sent from the Nucleus to ribosome where protein Nucleus to ribosome where protein is madeis made
Outline of making ProteinOutline of making Protein Directions on DNADirections on DNA DNA opens up and messenger RNA (mRNA) copies DNA opens up and messenger RNA (mRNA) copies
messagemessage mRNA is edited – some parts taken out (introns)mRNA is edited – some parts taken out (introns) mRNA goes out of nucleus to ribosomemRNA goes out of nucleus to ribosome mRNA attaches to ribosomemRNA attaches to ribosome Transfer RNA (tRNA) picks up an amino acid Transfer RNA (tRNA) picks up an amino acid tRNA attaches to mRNA matching complementary base tRNA attaches to mRNA matching complementary base
pairs at opposite end from amino acidpairs at opposite end from amino acid Amino acid is attached to other amino acids held by the Amino acid is attached to other amino acids held by the
ribosome to make a chain of proteinribosome to make a chain of protein When protein completely built unattached from ribosomeWhen protein completely built unattached from ribosome
Why we need RNA?Why we need RNA?
DNA cannot leave the nucleusDNA cannot leave the nucleus DNA gets transcribe into Messenger DNA gets transcribe into Messenger
RNA (mRNA)RNA (mRNA) Once edited, mRNA can leave the Once edited, mRNA can leave the
nucleus as a single strandnucleus as a single strand
Similarities and Similarities and differences DNA vs. RNAdifferences DNA vs. RNA
http://www.usask.ca/education/coursework/mcvittiej/bio30unit1/overheads/1.23.htm
1. A sequence of nucleotidesIn DNA (a gene) is transcribed to RNA in the nucleus
2. The RNA travels to the cytoplasm where it is translated into the specific amino acid sequece of a polypeptid
A codon is a three-base "word" that codes for one amino acid.
Several codons form a "sentence" that translates into a polypeptide.
Transcription playersTranscription players
DNADNA Messenger RNA (mRNA)Messenger RNA (mRNA) RNA polymeraseRNA polymerase
TranscriptionTranscription
mRNA editingmRNA editing
Translation playersTranslation players
mRNAmRNA Transfer RNATransfer RNA RibosomeRibosome Ribosomal RNARibosomal RNA
TranslationTranslation
Transcription-translation Transcription-translation animationsanimations
http://www.hhmi.org/biointeractive/dna/animations.html
Protein making analogy short movieProtein making analogy short movie
http://www.pbs.org/wgbh/nova/sciencenow/3210/02.html
00:54 – 03:20
What are MutationsWhat are Mutations
Any Any changechange in the in the nucleotide sequence nucleotide sequence of DNAof DNA
Two types of mutationsTwo types of mutations
Base substitutionBase substitutionBase deletionBase deletion
Types of mutationsTypes of mutations