General Biology 1004 Chapter 10 Lecture Handout, Summer ...dfrisby/downloads/ch10.pdf · General...

General Biology 1004 Chapter 10 Lecture Handout, Summer 2005Dr. Frisby

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Copyright ©2004 Pearson Education , Inc. publishing as Benjamin Cummings

PowerPoint® Lecture Slides forEssential Biology, Second Edition & Essential Biology with Physiology

Neil Campbell, Jane Reece, and Eric Simon

Presentation prepared by Chris C. Romero

CHAPTER 10CHAPTER 10Molecular Biology of the Gene

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• AIDS is one of the most challenging health problems facing the world today

BIOLOGY AND SOCIETY:SABOTAGING HIV

– Infection by HIV can cause AIDS

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• The drug AZT is effective at preventing the spread of HIV

Figure 10.1

Thymine(T)

AZT Part of a T nucleotide


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• DNA

THE STRUCTURE AND REPLICATION OF DNA

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• DNA and RNA are nucleic acids

DNA and RNA: Polymers of Nucleotides

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Figure 10.2

Phosphate group Nitrogenous base

Sugar

Nucleotide

Polynucleotide Sugar-phosphate backbone

Nitrogenous base(A,G,C, or T)

Thymine (T)

Phosphategroup

Sugar(deoxyribose)

DNA nucleotide


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• The four nucleotides found in DNA

• RNA has uracil (U) in place of thymine

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• James Watson and Francis Crick determined that DNA is a double helix

Watson and Crick’s Discovery of the Double Helix

Figure 10.3a(a) James Watson and Francis Crick

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• Watson and Crick used X-ray crystallography data to reveal the basic shape of DNA

Figure 10.3b

(b) Rosalind Franklin


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• The model of DNA is like a rope ladder twisted into a spiral

Figure 10.4Twist

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• Detailed representations of DNA

– Notice that the bases pair in a complementary fashion

Figure 10.5

Hydrogen bond

(a) (b) (c)

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• When a cell or organism reproduces, a complete set of genetic instructions must pass from one generation to the next

DNA Replication


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• Watson and Crick’s model for DNA suggested that DNA replicated by a template mechanism

Figure 10.6

Parental (old)DNA molecule

Daughter(new) strand

DaughterDNA molecule(double helices)

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• DNA can be damaged by ultraviolet light

Figure 10.7

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• DNA replication

Figure 10.8

Origin ofreplication

Origin ofreplication

Origin ofreplication Parental strand

Daughter strand

Bubble

Two daughter DNA molecules


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• DNA functions as the inherited directions for a cell or organism

THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN

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• An organism’s genotype, its genetic makeup is the sequence of nucleotide bases in DNA

How an Organism’s DNA Genotype Produces Its Phenotype

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• DNA specifies the synthesis of proteins in two stages

– Transcription

– Translation

Figure 10.9

DNANucleus

Transcription

RNA

Translation

ProteinCytoplasm


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• The one gene–one protein hypothesis states that the function of an individual gene is to dictate the production of a specific protein

• Archibald Garrod 1909

• Beadle and Tatum 1940s

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• The information, or “language,” in DNA is ultimately translated into the language of polypeptides

From Nucleotide Sequence to Amino Acid Sequence: An Overview

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• What is the language of nucleic acids?

Figure 10.10

DNA molecule

Translation

Polypeptide

Gene 1

Gene 2

Gene 3

DNA strand

Transcription

RNA

Codon

Amino acid


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• When DNA is transcribed, the result is an RNA molecule

• RNA is then translated into a sequence of amino acids in a polypeptide

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• What is the correspondence between the nucleotides of an RNA molecule and the amino acids of a polypeptide?

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• Triplets of bases


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• The genetic code is the set of rules relating nucleotide sequence to amino acid sequence

The Genetic Code

Figure 10.11

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• The genetic code is shared by all organisms

Figure 10.12

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Transcription: From DNA to RNA

• In transcription


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Figure 10.13a

RNApolymerase

RNA nucleotides

Newly madeRNA Direction of

transcription Templatestrand of DNA

(a) A close-up view of transcription

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• Transcription of an entire gene

Figure 10.13b

RNA polymerase

DNA of gene

PromoterDNA Initiation Terminator

DNA

RNAElongation

Area shownin part (a)

TerminationGrowingRNA

Completed RNA

RNApolymerase(b) Transcription of a gene

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• The “start transcribing” signal is a nucleotide sequence called a promoter

Initiation of Transcription

• The first phase of transcription is initiation


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• The second phase of transcription is elongation

RNA Elongation

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• The third phase of transcription is termination

Termination of Transcription

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• The eukaryotic cell processes the RNA after transcription

The Processing of Eukaryotic RNA


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• RNA processing includes

Figure 10.14

DNA

RNAtranscriptwith capand tail

mRNA

Exon Intron ExonIntron Exon

Cap

Intronsremoved Tail

Exons spliced together

Coding sequence

Nucleus

Cytoplasm

TranscriptionAddition of cap and tail

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• Translation

Translation: The Players

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• mRNA

Messenger RNA (mRNA)


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• tRNA

Transfer RNA (tRNA)

Figure 10.15

Amino acid attachment site

Hydrogen bond

RNA polynucleotide chain

AnticodonAnticodon

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• Ribosomes

Ribosomes

Figure 10.16a

tRNAbinding sites

P site A site

P A

Largesubunit

mRNAbindingsite

Smallsubunit

(a)

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• A fully assembled ribosome holds tRNA and mRNA for use in translation

Figure 10.16b

Next amino acidto be added topolypeptide

Growingpolypeptide

mRNA

tRNA

(b)


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• Translation is divided into three phases

Translation: The Process

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• The first phase brings together

Initiation

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• An mRNA molecule has a cap and tail that help it bind to the ribosome

Figure 10.17

Start of genetic message

Cap End

Tail


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• The process of initiation

Figure 10.18.1

MetInitiator tRNA

mRNA

Large ribosomalsubunit

Start codon

Small ribosomalsubunit

Initiation P siteA site

1

2

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• Step 1, codon recognition

Elongation

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• Step 2, peptide bond formation


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• Step 3, translocation

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Polypeptide

Amino acid

P site

AnticodonmRNA A site

Codons

Elongation

2

3 Translocation

Codonrecognition

Peptide bond formation

• The process of elongation

Figure 10.19

mRNAmovement

New peptidebond

1

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• Elongation continues until the ribosome reaches a stop codon

Termination


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• The flow of genetic information in a cell

Review: DNA RNA Protein

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Figure 10.20

1

2

3

4

Am ino acid attachment

5 Elongation

Init iation of translation

6 Termination

Transcription

RNA processing

RNA Polymerase

Nucleus

DNA

RNAtranscript

Intron

Tail

Intron

mRNA

CAP

tRNA

Enzyme

Amino acid

Ribosomal subunits

AnticodonCodon

Stop codon

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• In eukaryotic cells


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• Transcription and translation

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• A mutation

Mutations

Figure 10.21

Normal hemoglobin Sickle-cell hemoglobinGlu Val

Normal hemoglobin DNA Mutant hemoglobin DNA

mRNA mRNA

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• Mutations within a gene

Types of Mutations

Figure 10.22a

mRNA

Protein Met Lys Phe Gly Ala

(a) Base substitution

Met Lys Phe Ser Ala


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• Insertions and deletions

Figure 10.22b

Met Lys Leu Ala His

(b) Nucleotide deletion

mRNA

Protein Met Lys Phe Gly Ala

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• Mutations may result from

Mutagens

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• Although mutations are often harmful

Figure 10.23


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• Viruses sit on the fence between life and nonlife

VIRUSES: GENES IN PACKAGES

Figure 10.24

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• Bacteriophages, or phages

Bacteriophages

Figure 10.25

Head

Tail

Tail fiber

DNA of virus

Bacterialcell

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• Phages may have two reproductive cycles

Figure 10.26

Phage DNA

1

2

3

4

Phage DNA circularizes

New phage DNA andproteins are sythesized

5 Phage DNA inserts into the bacterialchromosome by recombination

Cell lyses,releasing phages

6 Lysogenic bacteriumreproduces normally,replicating the prophageat each cell division

7 Occasionally a prophagemay leave the bacterialchromosome

Bacterial chromosome (DNA)

Lytic cycle Lysogenic cycle

Prophage

Many cell divisions


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• Viruses that infect plants

Plant Viruses

Figure 10.27

Protein RNA

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• Genetic engineering methods

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• Virus studies help establish molecular genetics

Animal Viruses

• Molecular genetics helps us understand viruses

Figure 10.28

Membranousenvelope

RNA

Proteincoat

Proteinspike


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• The reproductive cycle of an enveloped virus

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Figure 10.29

VIRUS

Entry1

2

3

4

Uncoating

RNA synthesisby viral enzyme

5 RNA synthesis(other strand)

Proteinsynthesis

6 Assembly

7

Exit

Viral RNA (genome)

Protein spike

Protein coatEnvelope

Plasma membrane of host cell

mRNA

New viral proteins

Template

New viral genome

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• HIV is a retrovirus

HIV, the AIDS Virus

Figure 10.30a

EnvelopeProtein

Protein coat

RNA(two identical

strands)

Reversetranscriptase

(a) HIV


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1

23

4

5

6

DNA strand

Viral RNA Reverse transcriptase

Cytoplasm

Double-stranded DNA

Chromosomal DNA

Provirus DNA

Viral RNA and proteins

Nucleus

(b) The behavior of HIV nucleic acid in an infected cell

• How HIV reproduces inside a cell

Figure 10.30b

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• AIDS is

Figure 10.30c

(c) HIV infecting a white blood cell

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• Many new viruses have emerged in recent years

EVOLUTION CONNECTION:EMERGING VIRUSES

Figure 10.31

(a) Ebola virus

(b) Hantavirus


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• How do new viruses arise?

Figure 10.32

Chapter 10 Study Objectives

1. Describe the cause of AIDS. Explain how AZT prevents the spread of the disease.2. Explain what was and was not known about DNA by the early 1950s.3. Describe and compare the chemical compositions of DNA and RNA.4. Describe the key features of the overall shape of a DNA molecule. Explain how Watson

and Crick determined these features of DNA structure.5. Describe the process of DNA replication.6. Define transcription and translation. Explain why the hypothesis “one gene-one enzyme”

is not completely correct.7. Explain how the language of DNA directs the production of polypeptides.8. Explain how codons are used to construct polypeptides.9. Describe the steps transcription and the processing of RNA before it leaves the nucleus.10. Compare the structures and functions of mRNA, tRNA, and rRNA.11. Describe in detail the step-by-step process of translation.12. Distinguish between insertion, deletion, and substitution mutations. Explain how

mutations can be harmful or beneficial to organisms.13. Compare the lytic an lysogenic cycles of bacteriophages.14. Compare the life cycles of RNA and DNA viruses. Describe the spread, symptoms, and

treatment of viral diseases in plants and animals.15. Describe the reproductive cycle of retroviruses such as HIV.16. Explain how viruses might have first evolved and how new viral diseases evolve.

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