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