DNA, RNA, and the Flow of Genetic Information

Nucleic Acid Structure

What structural features do DNA and RNA What structural features do DNA and RNA share?share? Polymers of nucleotidesPolymers of nucleotides Each nucleotide contains sugar, Each nucleotide contains sugar,

phosphate, nitrogen containing basephosphate, nitrogen containing base Each nucleic acid contains 4 different Each nucleic acid contains 4 different

nucleotidesnucleotides

Nucleic Acid Structure

What differentiates What differentiates DNA from RNA?DNA from RNA? Type of pentose Type of pentose

sugarsugar

Nucleic Acid Structure

The nitrogen containing bases derived from The nitrogen containing bases derived from purine and pyrimidinepurine and pyrimidine

Nucleic Acid Structure

What makes up the backbone of the nucleic acids?What makes up the backbone of the nucleic acids?

Nucleic Acid Structure

What contributes to the stability of nucleic What contributes to the stability of nucleic acids?acids? Negative charge of phosphodiester bridgeNegative charge of phosphodiester bridge Repels nucleophilesRepels nucleophiles

What is the difference between a nucleotide What is the difference between a nucleotide and a nucleoside?and a nucleoside?

Nucleic Acid Structure

What are the DNA nucleotides?What are the DNA nucleotides? Deoxyadenosine-5-phosphateDeoxyadenosine-5-phosphate Deoxyguanosine-5-phosphateDeoxyguanosine-5-phosphate Deoxycytidine-5-phosphoteDeoxycytidine-5-phosphote Deoxythymidine-5-phosphateDeoxythymidine-5-phosphate

Nucleic Acid Structure

What are the RNA nucleotides?What are the RNA nucleotides? Adenosine-5-phosphateAdenosine-5-phosphate Guanosine-5-phosphateGuanosine-5-phosphate Cytidine-5-phosphateCytidine-5-phosphate Uridine-5-phosphateUridine-5-phosphate

Nucleic Acid Structure

How is the base bound How is the base bound to a sugar?to a sugar? -glycosidic -glycosidic

linkagelinkage

Nucleic Acid Structure

Nucleic acids show polarity and are always Nucleic acids show polarity and are always written in the 5’ to 3’ directionwritten in the 5’ to 3’ direction

What doe this What doe this photograph represent?photograph represent?

Nucleic Acid Structure

Nucleic Acid Structure

What are the major features of the double helix of What are the major features of the double helix of DNA?DNA? Two chains coiled around common axis Two chains coiled around common axis

running in opposite directionsrunning in opposite directions Bases on inside, sugar-phosphate on outsideBases on inside, sugar-phosphate on outside

Bases are 3.4Bases are 3.4Å apartÅ apartStructure repeats ever 34ÅStructure repeats ever 34ÅDiameter = 20ÅDiameter = 20Å

Nucleic Acid Structure

Base pairing existsBase pairing existsA with TA with TC with GC with G

How did the work How did the work of Chargaff support of Chargaff support this concept?this concept?

DNA Replication

DNA is said to DNA is said to replicate replicate semiconservatively. semiconservatively. What does this mean?What does this mean?

How did Meselson How did Meselson and Stahl demonstrate and Stahl demonstrate this to be true?this to be true?

DNA

How can the helical structure be disrupted?How can the helical structure be disrupted? HeatingHeating

What is TWhat is Tmm?? Melting temperature – half helical structure is Melting temperature – half helical structure is

destroyeddestroyed What is hyperchromism?What is hyperchromism?

Single stranded DNA absorbs UV light more Single stranded DNA absorbs UV light more effectively than double stranded DNAeffectively than double stranded DNA

DNA

DNA

DNA

Why is the ability to separate the two chains Why is the ability to separate the two chains of the double helix and reassociate them an of the double helix and reassociate them an important tool in the laboratory?important tool in the laboratory? hybridization experimentshybridization experiments

DNA

What is the difference between linear DNA What is the difference between linear DNA and circular DNA and where are each of and circular DNA and where are each of these forms found?these forms found? circular – ends of molecule are linkedcircular – ends of molecule are linked linear – human DNAlinear – human DNA circular – bacterial DNAcircular – bacterial DNA

DNA

What is supercoiled DNA?What is supercoiled DNA?

Nucleic Acid Structures

What are stem-loop structures?What are stem-loop structures?

Nucleic Acid Structures

Other complex Other complex structures of single-structures of single-stranded nucleic acids stranded nucleic acids formform

Nucleic Acid Structures

In some complex structures can get In some complex structures can get hydrogen bonds formed between non-hydrogen bonds formed between non-standard base pairsstandard base pairs

Nucleic Acid Structures

DNA Replication

What is DNA polymerase?What is DNA polymerase? enzyme that catalyzes addition of DNA nucleotides enzyme that catalyzes addition of DNA nucleotides

to a growing chain of DNAto a growing chain of DNA (DNA)(DNA)nn + dNTP (DNA) + dNTP (DNA)n+1 n+1 + PP+ PPii

What besides the enzyme is needed for DNA What besides the enzyme is needed for DNA synthesis?synthesis? templatetemplate primerprimer activated nucleotidesactivated nucleotides

DNA Replication

What is the nature of the reaction catalyzed by What is the nature of the reaction catalyzed by DNA polymerase?DNA polymerase?

DNA Replication

What else can some DNA polymerases do?What else can some DNA polymerases do? remove mismatched nucleotidesremove mismatched nucleotides

RNA Viruses

What is the difference between and RNA What is the difference between and RNA virus and a retrovirus?virus and a retrovirus? RNA viruses replicate via an RNA RNA viruses replicate via an RNA

directed RNA polymerasedirected RNA polymerase retroviruses use reverse transcriptase to retroviruses use reverse transcriptase to

replicatereplicate Examples of each?Examples of each?

Replication of Retrovirus

Gene Expression

How does RNA facilitate gene expression?How does RNA facilitate gene expression? m-RNA – carries information from DNAm-RNA – carries information from DNA t-RNA – carries amino acids to site of t-RNA – carries amino acids to site of

protein synthesisprotein synthesis r-RNA – major component of ribosome r-RNA – major component of ribosome

where proteins are madewhere proteins are made snRNA – (in eucaryotes only) – splices snRNA – (in eucaryotes only) – splices

RNARNA

Transcription

What does RNA polymerase do and how does it work?What does RNA polymerase do and how does it work?

Transcription

How does RNA polymerase differ from How does RNA polymerase differ from DNA polymerase?DNA polymerase? doesn’t require primerdoesn’t require primer doesn’t contain nuclease activitydoesn’t contain nuclease activity

Transcription

What are promoter sites and where are they What are promoter sites and where are they located?located? regions of DNA that bind RNA polymerase and regions of DNA that bind RNA polymerase and

determine where transcription beginsdetermine where transcription begins

Transcription

How does RNA How does RNA polymerase know polymerase know when to stop when to stop transcribing?transcribing? terminator sequenceterminator sequence rho proteinrho protein

Transcription

What happens to m-RNA in eukaryotes after What happens to m-RNA in eukaryotes after transcription?transcription?

Transcription

How does t-RNA serve as an adaptor molecule?How does t-RNA serve as an adaptor molecule?

Transcription

What do we know about the genetic code?What do we know about the genetic code? three nucleotides code for an amino acidthree nucleotides code for an amino acid code doesn’t overlapcode doesn’t overlap no punctuationno punctuation code is degeneratecode is degenerate

Genetic Code

Translation What are the start and stop signals for translation?What are the start and stop signals for translation?

stop codons – UAA, UCA,UAGstop codons – UAA, UCA,UAG

Genetic Code

What evidence suggests that the genetic What evidence suggests that the genetic code is universal?code is universal? one can use machinery of one species to one can use machinery of one species to

translate m-RNA of a different speciestranslate m-RNA of a different species There are some variations in genetic codeThere are some variations in genetic code

mitocondrial DNAmitocondrial DNA DNA from cilliatesDNA from cilliates

Genetic Code

What are introns and exons?What are introns and exons? introns – non-coding sequences of DNAintrons – non-coding sequences of DNA exons – coding sequences of DNAexons – coding sequences of DNA

RNA Processing

How are introns correctly removed before translation?How are introns correctly removed before translation? splicosomes – proteins and small RNA moleculessplicosomes – proteins and small RNA molecules

Exons and Introns

Why are many genes in higher eukaryotes Why are many genes in higher eukaryotes discontinuous?discontinuous? exons code functional domains in exons code functional domains in

proteinsproteins can shuffle exons to produce new can shuffle exons to produce new

proteinsproteins can generate related proteins by splicing can generate related proteins by splicing

m-RNA differentlym-RNA differently