chapter 7 · what is dna? section 7.1 dna stored information for protein production. dna (genotype)...

Chapter 7 DNA Structure and Gene

Function

DNA bursting from bacterial cell © Dr. Gopal Murti/Science Source

Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

What is DNA?

Section 7.1

DNA stored information for protein production.

DNA (genotype)

RNA

Protein (phenotype)

Rosalind Franklin

Watson & Crick

Figure 17.2

Double-stranded DNA

Histones

Chromatinmaterial:not visibleduringInterphase

One chromatid

Its sisterchromatid

Centromere

Chromosome: visible during mitosis

DNA Review

Base pair

Phosphate

Sugar

Nucleotide

Figure 2.24

• DNA Nucleotide

• Deoxyribose sugar

• Phosphate group

• Nitrogenous base

• A, G, C, T

DNA Structure

Sugars &

phosphates

Nitrogenous Bases

DNA Base Pair Rules(Chargaff’s Rules)

DNA Base Pairing

Section 7.1 Figure 7.5

Hydrogen bonds connect complementary DNA strands.

Hydrogen bonds

DNA Is a Double Helix

RNA Review

• RNA Nucleotide

• Ribose sugar

• Phosphate group

• Nitrogenous base

• A, G, C, U

Review: DNA & RNA Comparison


Nitrogenous Bases

1. Which nitrogenous base is only found in RNA?

uracil

2. Which nitrogenous base is only found in DNA?

thymine

3. Which nitrogenous bases are found in both DNA & RNA?

adenine/guanine/cytosine

What is the main function of DNA?

A. encode proteins B. produce ATP C. speed up cell reactionsD. provide structural support to the cellE. All of the choices are correct.

Flower: © Doug Sherman/Geofile/RF

• Prokaryotic cells• Transcription

DNA RNA

• Translation

RNA proteins

Protein Synthesis

Protein Synthesis

• Eukaryotic cells• Transcription

DNA RNA

• RNA Processing

Modify pre-mRNA

• Translation

RNA proteins

http://www.saddleback.edu/faculty/steh/bio20folder/ProteinSynthesis.mpg

Genetic Code

• Codon• mRNA

Fig. 17-6

(a) Tobacco plant expressing

a firefly gene

(b) Pig expressing a

jellyfish gene

Protein Production Starts with DNA


Transcription: DNA RNA• 3 types of RNA

Translation: RNA Protein


Fig. 17-1

Protein Production Starts with DNA


Protein analogy Cooking

Modification to ingredients?

Transcription Uses DNA to Create RNA

Section 7.4 Figures 7.8, 7.9

How does DNA pair with RNA?

Fig. 17-7

Promoter Transcription unit

Start pointDNA

RNA polymerase

5533

Initiation1

2

3

5533

Unwound

DNA

RNAtranscript

Template strand

of DNA

Elongation

Rewound

DNA

5

55

5

5

33

3

3

RNA

transcriptTermination

5533

35Completed RNA transcript

Newly made

RNA

Template

strand of DNA

Direction oftranscription(“downstream”)

3 end

RNA

polymerase

RNA nucleotides

Nontemplate

strand of DNAElongation

Transcription Overview


RNA polymerase binds to the promoter region

DNA

Initiation

RNA polymerase enzyme

Promoter DNA template strand

Initiation

Figure 7.10Section 7.4


RNA complementary to DNAElongation

RNA polymerase

RNA

DNA

Elongation

Section 7.4

3’

5’

5’

5’3’

3’

Figure 7.10


Termination

RNA polymerase

DNA

TerminatorRNA

Termination


RNA, DNA, and RNA polymerase separate.

DNA becomes a double helix again.


The cell produced an RNA copy of a gene!

Termination

RNA polymerase

DNA

TerminatorRNA

Termination


Fig. 17-7

Promoter Transcription unit

Start pointDNA

RNA polymerase

5533

Initiation1

2

3

5533

Unwound

DNA

RNAtranscript

Template strand

of DNA

Elongation

Rewound

DNA

5

55

5

5

33

3

3

RNA

transcriptTermination

5533

35Completed RNA transcript

Newly made

RNA

Template

strand of DNA

Direction oftranscription(“downstream”)

3 end

RNA

polymerase

RNA nucleotides

Nontemplate

strand of DNAElongation

Transcription Overview

If DNA reads 5' - TACTTCAAAATC - 3‘

• What are the transcribed RNA bases?

• How many codons?

• How many amino acids will be present

after translation?

RNA Is Processed in the Nucleus

Figure 7.11

Poly A tail and mRNA cap are added to the RNA.

Section 7.4


Introns are removed from the RNA molecule.

Introns

Exons



The RNA then leaves the nucleus. Onward to

translation!


Fig. 18-11

or

RNA splicing

mRNA

PrimaryRNAtranscript

Troponin T gene

Exons

DNA

Alternative Splicing

If the DNA template strand has the following sequence, what would be the nucleotide sequence of the complementary RNA molecule produced in transcription?

Template strand: AGTCTT

A. AGTCTTB. AGUCUUC. TCAGAAD. TCUGUUE. UCAGAA


7.4 Mastering Concepts

How is mRNA modified before it leaves the nucleus of a eukaryotic cell?

DNA bursting from bacterial cell © Dr. Gopal Murti/Science Source

Translation Builds the Protein


Now let’s look at how a ribosome uses RNA to produce a protein.


Figure 7.12

A

A A

A AG

G G

G UU C

CTT T C

C

DNA template strandDNA

TRANSCRIPTION

mRNA

TRANSLATION

Protein

CodonCodonCodon

Lysine ValineSerine

Polypeptide (amino acid sequence)

A codon is a three-nucleotide sequence that encodes one amino acid.

Section 7.5


U

C

A

G

U C A G

Firs

t le

tter

of

cod

on

U

C

A

G

U

C

A

G

U

C

A

G

U

C

A

G

Third

letter of co

do

nA A AG G UU CC

mRNA

TRANSLATION

Protein

CodonCodonCodon

Lysine ValineSerine

Polypeptide (amino acid sequence)

The Genetic Code

Second letter of codon

UUU

UUC

UUA

UUG

CUU

CUC

CUA

CUG

AUU

AUC

AUA

AUG

GUU

GUC

GUA

GUG

UAU

UAC

CCA

CCG

UAA

UCU

UCC

UCA

UCG

CCU

CCC

UAG

UGU

UGC

UGA

UGG

CAU

CAC

CAA

CAG

CGU

CGC

CGA

CGG

ACU

ACC

ACA

ACG

AAU

AAC

AAA

AAG

AGU

AGC

AGA

AGG

GCU

GCC

GCA

GCG

GAU

GAC

GAA

GAG

GGU

GGC

GGA

GGG

Leucine (Leu; L)

Phenylalanine (Phe; F)

Leucine (Leu; L)

Isoleucine (Ile; I)

Start Methionine (Met; M)

Valine (Val; V)

Serine (Ser; S)

Proline (Pro; P)

Proline (Pro; P)

Proline (Pro; P)

Tyrosine (Tyr; Y)

Histidine (His; H)

Glutamine (Gln; Q)

Asparagine (Asn; N)

Lysine (Lys; K)

Aspartic acid (Asp; D)

Glutamic acid (Glu; E)

Cysteine (Cys; C)

Tryptophan (Trp; W)

Stop

Arginine (Arg; R)

Serine (Ser; S)

Arginine (Arg; R)

Glysine (Gly; G)

Stop

Stop

The genetic code shows which mRNA codons correspond to which amino acids.


Translation

Cast members of Protein Synthesis

• mRNA


Transfer RNA (tRNA) translate the genetic code.

tRNA: © Tom Pantages/PhototakeSection 7.5 Figure 7.13

Translation



• Ribosome• Large subunit

P site

A site

• Small subunit

Translation



Translation

Protein Synthesis – Initiation

1. Binding of mRNA, 1st tRNA w/ aa and small ribosome

2. Binding of the large subunit


Translation

Protein Synthesis

Elongation• Codon recognition

Type of bond?

• Peptide bond formation

• tRNA in P-site leaves

• tRNA in A-site has

protein

• translocation


Translation

Protein Synthesis – Termination

Polyribosomes


PolypeptidemRNA Ribosome

SEM (false color) 50 nm

Ribosomes: © Kiseleva and Donald Fawcett/Visuals Unlimited

Translation is efficient when multiple ribosomes attach to an mRNA molecule simultaneously.


Fig. 17-21

Ribosome

mRNA

Signalpeptide

Signal-recognitionparticle (SRP)

CYTOSOLTranslocationcomplex

SRPreceptorprotein

ER LUMEN

Signalpeptideremoved

ERmembrane

Protein

Secretory proteins – endomembrane system

Protein Synthesis


• Amino acid

• tRNA UAC anticodon

• mRNA codon

• DNA

Mutations Change DNA

A mutation is a change in a cell’s DNA sequence. Mutations come in several varieties.

Section 7.7 Figure 7.20Wild fly: © Andrew Syred/Science Source; Mutant fly: © Science VU/Dr. F. R. Turner/Visuals Unlimited


A point mutation changes one or a few base pairs in a gene.

Table 7.2Section 7.7

Normal cells: © Micro Discovery/Corbis; Sickled cells: © Dr. Gopal Murti/Science Source

Normal red blood cells

No aggregation

of hemoglobin

molecules

SEM

Pro Glu Glu

6 µm

Sickled red blood cells

Abnormal

aggregation

of hemoglobin

molecules

Pro Val Glu6 µm

G G A C T C C T T

C C U G A G G A A

G G A C A C C T T

C C U G U G G A A

SEM

Point Mutation -Substitution

Figure 7.21


Section 7.7


Wildtype = original nucleotide sequence

Substitution = changed nucleotide(s)

In lab 1 base changeSalt instead of sugar

Silent mutation?



“Frameshift”mutations affect multiple codons.

Insertion of one nucleotide changes every codon after the insertion.


Figure 10.16B

Normalgene

Nucleotidesubstitution

Nucleotidedeletion

Nucleotideinsertion

Inserted

Deleted

mRNA

Protein Met

Met

Lys Phe

Lys Phe

Ala

Ala

Gly

Ser

A U G A A G U U U G G C G C A

G C G C AAG U U UA U G A A

Met Lys Ala HisLeu

G U UA U G A A G G C G C A U

U

Met Lys Ala HisLeu

G U UA U G A A G G CU G G C

Frameshift Mutations

But mutations are not always harmful!

• Mutations create different versions of genesAlleles alternative versions of the same gene

• Genetic variation is important for evolution.

• What determines if a mutation is advantageous or not?


Section 7.7 Figure 7.23Grapefruit: © Erich Schlegel/Dallas Morning News/Corbis; rice: © Pallava Bagla/Corbis; cotton: © Scott

Olson/Getty Images

Chapter 8 DNA Replication, Binary Fission,

and Mitosis

World’s tallest man © Frederic J. Brown/AFP/Getty Images

Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

Two Types of Cell Division Interact in the Sexual Life Cycle

Section 8.1

Sex cells combine at fertilization.

Figure 8.1

Mitosis Has Many Roles

Section 8.1

1) Grow and develop2) repair tissues3) regenerate lost body parts4) Some organisms reproduce asexually by mitosis

Mitosis Has Many Roles


Mitosis produces the cells that build the human body.

Day 1 zygote: © Pascal Goetgheluck/Science SourceDay 2, 3 zygote: © Richard G. Rawlins, Ph.D./ Custom Medical Stock PhotoMiddle and bottom row photos: Bradley R. Smith, Ph.D.

Cell Death Is Part of Life

Section 8.1

Apoptosis, or cell death, carves out distinctive structures.

Figure 8.3Duckling: © GK hart/Vikki Hart/Getty Images RF

Mitosis and Apoptosis Work Together

Section 8.1

Mitosis adds new cells while apoptosis removes them, allowing tissues to renew themselves.

Shortly after fertilization, a zygote divides into two identical cells. What type of cell division produces these two cells?

A. mitotic cell divisionB. meiotic cell divisionC. apoptosis


DNA Replication Precedes Cell Division

Section 8.2

For each of the daughter cells from this division to have identical DNA, the cell must first replicate its genome, all of the cell’s genetic material.

Tumor cells: © Steve Gschmeissner/SPL/Getty Images RF

Figure 17.1

Mitosis

Nucleus divides

Cytokinesis

Cell divides

Cell prepares for division.Growth continuesslowly.

Primary period

of cell growth.

G2G1

S

DNA is duplicated.Growth continuesslowly.

M

G0

Cell Cycle

• Interphase

• Mitotic phase

(karyokinesis)

– Prophase

– Metaphase

– Anaphase

– Telophase

• Cytokinesis

DNA Replication

• When does DNA

replication take place?

• Why does DNA

replication take place?

DNA Replication Overview

Centromere

Figure 17.4

Keys:

= Cytosine

= Adenine

= Guanine

= Thymine

Replication

bubble

Parent DNA

molecule

2 complete

daughter DNA

molecules

Parent

strands

New

complementary

strands

b) The unwinding and the formation of new strands occur

simultaneously at many sites on the DNA molecule.

The sites of replication expand outward until they join. For

simplicity the two strands are shown as parallel in (b),

but in actuality they form a helical shape as shown in (a).

Parent strand New

(daughter)

strands

forming

Parent strand

a) The double-stranded DNA unwinds, and each single

strand serves as a template for a new complementary

strand.

Why many origins of replication?

DNA Replication Enzymes

1. Helicase

2. Single strand binding protein

3. Primase

4. DNA polymerase

5. DNA ligase

1. Looks for start points

Opens DNA

2. Helps keep DNA opened

3. Primes DNA replication

10 RNA nucleotides

4. a) Copies DNA

b) converts RNA nucleotides to DNA nucleotides

c) proofreads

d) corrects errors

5. Joins DNA sections (fragments)


Section 8.2

Semi conservative:½ old

&½ new

Figure 8.6

http://www.saddleback.edu/faculty/steh/bio20folder/DnaReplication.mpg


Section 8.2

1) Helicases 2) Binding proteins

Figure 8.5



Section 8.2

3) Primase

Figure 8.5

Priming for DNA Replication

• Primase RNA primer


Section 8.2

4) DNA polymerase

New strand 5’ 3’

Figure 8.5

DNA Elongation

Replication Fork


Section 8.2

Leading Strand: synthesis is continuous.

Figure 8.5

Leading & Lagging Strands


Section 8.2

Lagging Strand: opposite direction from helicase movement. Strand synthesis is discontinuous.

Figure 8.5


Section 8.2

4) DNA polymerase RNA primer with DNA

5) Ligases

Figure 8.5


Section 8.2

Semi conservative:½ old

&½ new

Figure 8.6


DNA Replication Enzymes

1. Helicase

2. Single strand binding protein

3. Primase

4. DNA polymerase

5. DNA ligase

1. Looks for start points

Opens DNA

2. Helps keep DNA opened

3. Primes DNA replication

10 RNA nucleotides

4. a) Copies DNA

b) converts RNA nucleotides to DNA nucleotides

c) proofreads

d) corrects errors

5. Joins DNA sections (fragments)

Figure 10.22A

DNA enters

cell

A fragment ofDNA from anotherbacterial cell

Bacterial chromosome(DNA)

Prokaryotic Genetic Diversity

Horizontal Gene Transfer increases bacterial diversity

1. Transformation

Figure 10.22B

Phage

A fragmentof DNA fromanotherbacterial cell(former phage host)

Horizontal Gene Transfer

2. Transduction

Figure 10.22C

Mating bridge

Sex pili

Donor cell Recipient cell


3. Conjugation

Figure 10.22D

Donated DNA Crossovers Degraded DNA

Recombinantchromosome

Recipient cell’schromosome


3. Conjugation

Figure 10.20A

Envelope

Glycoprotein

Protein coat

RNA(two identicalstrands)

Reversetranscriptase(two copies)

HIV

HIV & Protein Synthesis

Figure 10.18_UN

Mumps Virus

•MMR vaccine (measles, mumps & rubella)

Polio

2

Figure 10.18

Viral RNA (genome)

Glycoprotein spike

Protein coat

Membranousenvelope

Entry CYTOPLASM

Uncoating

Plasmamembraneof host cell

1

3

54

6

Proteinsynthesis

Viral RNA(genome)

RNA synthesisby viral enzyme

mRNA

Newviral proteins

Assembly

New viralgenome

Template

RNA synthesis(other strand)

Exit

7

6

Figure 10.19

Emerging Viruses

How do they come arise?

•Mutations

•Contact btn species

•Spread from isolated

populations

HIV, West Nile Virus, SARS, H1N1 – swine flu

Figure 10.UN03

DNA

(b)

is a polymermade from

monomers called

is performedby an

enzyme called(c)

(a)

(d)

(e)

(f)

comesin three

kinds called

use amino-acid-bearingmolecules called

is performedby structures

called (h)

molecules arecomponents of

RNA

Protein

(g)

(i)

one or more polymersmade from

monomers called

chapter 7 · what is dna? section 7.1 dna stored information for protein production. dna (genotype)...

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