Chapter 22 Lecture Outline - Napa Valley College · Chapter 22 Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes

1

Chapter 22

Lecture Outline

See separate PowerPoint slides for all figures and tables pre-

inserted into PowerPoint without notes.

Copyright © 2016 McGraw-Hill Education. Permission required for reproduction or display.

2

DNA Biology and

Technology

3

Points to ponder

• What are three functions of DNA?

• Review DNA and RNA structure.

• What are the three major types of RNA and their functions?

• Compare and contrast the structure and function of DNA and RNA.

• How is DNA replicated?

• Describe transcription and translation in detail.

• Describe the genetic code.

• Review protein structure and function.

• What are the four levels of regulating gene expression?

4

• What did we learn from the Human Genome Project, and where do we go from here?

• What is ex vivo and in vivo gene therapy?

• Define biotechnology, transgenic organisms, genetic engineering, and recombinant DNA.

• What are some uses of transgenic bacteria, plants, and animals?

Points to ponder

5

What does DNA do?

1. It replicates to be passed on to the next

generation.

2. DNA stores information.

3. It undergoes mutations to provide genetic

diversity.

22.1 DNA and RNA Structure and Function

6

DNA structure: A review

• It is a double-stranded helix.

• DNA is composed of repeating nucleotides

(made of a pentose sugar, phosphate, and a

nitrogenous base).

• Sugar and phosphate make up the backbone,

while the bases make up the “rungs” of the

ladder.

• Bases have complementary pairing: cytosine

(C) pairs with guanine (G), and adenine (A)

pairs with thymine (T).


7

DNA structure

Figure 22.1 The structure of DNA.


Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

T

S

P

T

S

P

P

S

P

S

S

S

S

S

S

b. Ladder structure a. Double helix c. One pair of bases

P S

P

P

S

S

S

P

P

O

C

C

C C

C

T A

G

C

T A

C G

A

T

T A

A T

deoxyribose

5′ end

3′ end

3′ end

5′ end

5′ end 3′ end

5′

4′ 1′

3′ 2′

1′

2′ 3′

4′

5′

1′

2′

4′

5′

phosphate pyrimidine base purine base

P

P OH

OH

3′

3′

P

P

8

How is DNA replicated?

• The two strands unwind as the H bonds are

broken.

• Complementary nucleotides are added to

each strand by DNA polymerase.

• Each new double-stranded helix is made of

one new strand and one old strand

(semiconservative replication).

• The sequence of bases makes each

individual unique.

A

A

A

T

G

G

G

C

C


9

DNA replication

Figure 22.2 Semiconservative replication.


10

RNA structure and function

• It is single-stranded.

• RNA is composed of repeating nucleotides.

• Sugar-phosphate is the backbone.

• Bases are A, C, G, and uracil (U).


11

• Three types of RNA

– Messenger RNA (mRNA) carries genetic

information from DNA to the ribosomes.

– Ribosomal RNA (rRNA) joins with proteins

to form ribosomes.

– Transfer RNA (tRNA) transfers amino

acids to a ribosome where they are added

to a forming protein.


RNA structure and function

12

RNA structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

S

S

S

S

G

U

A

C

G

U

A

C

ribose one nucleotide

P

P

P

P

Base is

uracil instead

of thymine

Figure 22.4 The structure of RNA.


13

Types of RNA

Figure 22.9 The roles of all three forms of RNA in translation.



U C A

U G G A

large ribosomal

subunit

a. An mRNA is threaded between

ribosomal subunits and a

polypeptide extends to the side.

mRNA

tRNA

P site

anticodon

polypeptide

polypeptide

b. A ribosome has two binding sites where codons

bind to anticodons. A tRNA bearing a polypeptide

is at the P site. A new tRNA amino acid is

approaching the A site.

c. A tRNA amino acid is coming to

the ribosome. Upon arrival, its

anticodon, CUG, will bind to its

codon, GAC.

anticodon

A site

codon

val

tryp

ala

ser

met

small ribosomal

subunit

asp

C A

14

Comparing DNA and RNA

• Similarities

– They are nucleic

acids.

– They are made of

nucleotides.

– The have sugar-

phosphate

backbones.

– They are found in

the nucleus.

• Differences

– DNA is double-

stranded while RNA

is single-stranded.

– DNA has T while

RNA has U.

– RNA is also found in

the cytoplasm as

well as the nucleus

while DNA is not.


15

Proteins: A review

• Proteins are composed of subunits called amino acids.

• The sequence of amino acids determines the shape of the protein.

• They are synthesized at the ribosomes.

• Proteins are important for diverse functions in the body including hormones, enzymes, and transport.

• They can denature, causing a loss of function.

22.2 Gene Expression

16

2 steps of gene expression

1. Transcription –

DNA is read to

make a mRNA in

the nucleus

2. Translation –

mRNA is read to

make a protein in

the cytoplasm

Figure 22.5 Summary of gene expression.


transcription

innucleus

DNA

mRNA

translation

at ribosome

polypeptide

O O O

Proline Aspartic acid Serine

N C C N C C N C C

R1 R2 R3

codon 3 codon 2 codon 1

3′

5′

5′

C

G

G

C A

G

C C

G

C

G T T

A G

C G

C

G C A C C C A G C

template strand

nontemplate strand

3′

3′

5′


17

The genetic code

• It is made of four

kinds of bases.

• Bases act as a code

for amino acids used

in translation.

• Every three bases of

the mRNA is called a

codon; a typical

codon specifies a

particular amino acid

in translation.

Figure 22.6 The genetic code.



Second Base

arginine

CGG arginine

AGU serine

AGC serine

arginine

AGG arginine

GGU glycine

GGC glycine

glycine

GGG glycine

UGC cysteine

UGG tryptophan

CGU arginine

CGC arginine

stop

CAC histidine

glutamine

CAG glutamine

AAU asparagine

AAC asparagine

lysine

AAG lysine

GAU aspartic acid

GAC

GAG

UUU phenylalanine

UUC phenylalanine

leucine

UUG leucine

CUU leucine

CUC leucine

leucine

CUG leucine

AUU isoleucine

AUC isoleucine

isoleucine

GUU valine

GUC valine

valine

GUG valine

UCC serine

serine

UCG serine

CCU proline

CCC proline

proline

CCG proline

ACU threonine

ACC threonine

threonine

ACG threonine

GCU alanine

GCC alanine

alanine

GCG alanine

UAC tyrosine

CAU histidine

stop

UAG stop

UCU serine

UAU tyrosine

UGU cysteine

U

C

A

G

U

C

A

G

U

C

A

G

U

C

A

G

U

C

A

G

U C A G

First

Base

Third

Base

AUG (start)

methionine

UGA UAA

CGA CUA

UUA UCA

CCA CAA

AUA ACA AAA AGA

GUA GCA GAA GGA

aspartic acid

glutamic acid

glutamic acid

18

1. Transcription

• mRNA is made from a DNA template.

• mRNA is processed before leaving the nucleus.

• mRNA moves to the ribosomes to be read.

Figure 22.7 Transcription of DNA into mRNA.



template

strand

direction of polymerase

movement

RNA

polymerase

DNA

template

strand

mRNA

transcript

to RNA processing

G

A

A

A

A

A

A

C

C

C

C

T

T

T

T

T

C 3′

5′

5′

5′

3′

3′

19

Processing of mRNA after transcription

Modifications of mRNA

• One end of the RNA is capped.

• Introns are removed.

• A poly-A tail is added.


20 Figure 22.8 mRNA processing.


Processing of mRNA after transcription Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

DNA

exon exon exon

transcription intron intron

pre-mRNA

exon exon exon

intron intron

poly-A tail cap intron intron

exon exon exon

exon exon exon

poly-A tail

pre-mRNA

splicing

cap

intron RNA

mRNA

poly-Atail cap

nuclear pore

in nuclear envelope

nucleus

cytoplasm

spliceosome

5′

5′

5′

5′ 3′

3′

3′

3′

21

2. Translation

3 steps 1. Initiation: mRNA binds to the small ribosomal

subunit and causes the two ribosomal units to associate

2. Elongation: polypeptide lengthens

• tRNA picks up an amino acid.

• tRNA has an anticodon that is complementary to the codon on the mRNA.

• tRNA anticodon binds to the codon and drops off an amino acid to the growing polypeptide.

3. Termination: a stop codon on the mRNA causes the ribosome to fall off the mRNA


22

Visualizing the 3 steps of translation

Figure 22.10 Formation of

the polypeptide during

translation.


23

Overview of transcription and translation

3. mRNA moves into

cytoplasm and becomes

associated with ribosomes.

Translation 1. DNA in nucleus

serves as a template

for mRNA.

2. mRNA is processed

before leaving the nucleus.

primary

mRNA

mature

mRNA

DNA

TRANSCRIPTION

introns

exons


C C

G G

G

U

A

U U U

4. tRNAs with

anticodons carry

amino acids

to mRNA.

nuclear pore

mRNA

peptide

amino

acids

5. Anticodon–codon

complementary

base pairing occurs.

anticodon

codon ribosome

A A A

large and small

ribosomal subunits

tRNA

6. Polypeptide synthesis

takes place one amino

acid at a time.

Figure 22.12 Summary of transcription and translation.


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Regulation of gene expression 5 levels

1. Pretranscriptional control (nucleus)

• e.g., chromatin density and DNA accessibility

2. Transcriptional control (nucleus)

• e.g., transcription factors

3. Posttranscriptional control (nucleus)

• e.g., mRNA processing

4. Translational control (cytoplasm)

• e.g., differential ability of mRNA to bind ribosomes

5. Posttranslational control (cytoplasm)

• e.g., changes to the protein to make it functional


25

Regulation of gene expression

Figure 22.13 Control of gene expression in eukaryotic cells.



Cytoplasm

Nucleus

nucleosome

signal

chromatin

packing

DNA

DNA unpacking

mRNA processing

mRNA translation

Prosttranslational control

primary mRNA

maturem RNA nuclear

envelope

nuclear

pore

polypeptide

functional

protein

degraded

protein

DNA transcription exon intron

26

DNA Technology

1. Gene cloning through recombinant DNA

2. Polymerase chain reaction (PCR)

3. DNA fingerprinting

4. Biotechnology products from bacteria,

plants, and animals

22.3 DNA Technology

27

DNA Technology terms • Genetic engineering – altering DNA in bacteria,

viruses, plants, and animal cells through recombinant DNA technology

• Recombinant DNA – contains DNA from two or more different sources

• Transgenic organisms – organisms that have a foreign gene inserted into them

• Biotechnology – using natural biological systems to create a product or to achieve an end desired by humans

22.3 DNA Technology

28

DNA Sequencing

• The order of nucleotides in a DNA sequence is

determined

• 1970s: performed manually using dye-terminator

substances

• Now performed using dyes attached to

nucleotides, with a laser and computerized

machine to determine sequence

22.3 DNA Technology

29

Automated DNA sequencer and

an electropherogram Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Small section of a genome

(sequencer): © Lawrence Berkeley Nat’l Lab/Roy Kaltschmidt, photographer

Figure 22.14 Automated

DNA sequencer and an

electropherogram.

22.3 DNA Technology

30

Polymerase chain reaction (PCR)

• Polymerase chain reaction is used to

clone small pieces of DNA.

• It is important for amplifying DNA for

analysis such as in DNA fingerprinting.

22.3 DNA Technology

31

Polymerase chain reaction (PCR)

Figure 22.15 The polymerase chain reaction.

22.3 DNA Technology


5´

5´

5´

5´

5´

5´

5´

5´

3´

3´

3´

3´

3´

3´

3´

3´

5´

5´

5´

5´

3´

3´

3´

3´

5´

5´

5´

5´

3´

3´

3´

3´

5´

5´

3´

3´

5´

5´

3´

3´

5´

5´

3´

3´

DNA is denatured

Into single strands

1. Sample is first

heated to

denature DNA.

2. DNA is cooled to a

lower temperature

to allow annealing

of primers.

3. DNA is heated to

72°C, the optimal

temperature for

Taq DNA

polymerase to

extend primers.

Cycle 2:

4 copies Cycle 3:

8 copies

DNA strand

DNA segment

to be amplified

Primers anneal to DNA Taq DNA polymerase

5´

5´

5´

5´

5´

5´

5´

5´

3´

3´

3´

3´

3´

3´

3´

3´

5´

5´

5´

5´

3´

3´

3´

3´

32

DNA fingerprinting

• Fragments are

separated by their

charge/size ratios.

• It results in a distinctive

pattern for each

individual.

• It is often used for

paternity testing, or to

identify an individual at a

crime scene or unknown

body remains.


Collect DNA

Use gel electrophoresis to identify criminals

marker Suspect B Suspect A

Crime scene

suspect B

suspect A

crime scene evidence

Perform PCR on repeats

16

re

pe

ats

12

re

pe

ats

12

re

pe

ats

12

re

pe

ats

16

re

pe

ats

12

re

pe

ats

Figure 22.16 PCR and electrophoresis used for DNA fingerprinting.

22.3 DNA Technology

33

Gene cloning

• Recombinant DNA – contains DNA from two or more different sources that allows genes to be cloned

• Bacteria used to clone the human insulin gene – Restriction enzyme is used to cut the vector

(plasmid) and the human DNA with the insulin gene.

– DNA ligase seals together the insulin gene and the plasmid.

– Bacterial cells take up plasmid, the gene is copied, and the product can be made.

22.3 DNA Technology

34

Visualizing gene cloning

Figure 22.17 Cloning of a human gene.

22.3 DNA Technology


Bacteria produce a product.

bacterium

human DNA

human cell

insulin gene

4a 4b

DNA ligase seals the insulin gene into the plasmid.

Gene cloning occurs.

insulin

1

2

3

recombinant DNA

plasmid (vector)

Host cell takes up recombined plasmid.

Restriction enzyme cleaves DNA.

35

Biotechnology products: Transgenic organisms

• Important uses

– Production of:

• Insulin

• Human growth hormone (HGH)

• Clotting factor VIII

• Tissue plasminogen activator (t-PA)

• Hepatitis B vaccine

– Naturally-occurring oil-degrading bacteria

can be made more effective through

genetic engineering

22.3 DNA Technology

36

Biotechnology products: Transgenic organisms

Figure 22.18 Transgenic organisms.

22.3 DNA Technology

37

Biotechnology products:

Transgenic plants

• Important uses – Produce human proteins in their seeds such

as hormones, clotting factors, and antibodies

– Plants resistant to herbicides

– Plants resistant to insects

– Plants resistant to frost

22.3 DNA Technology

38

Genetically engineered plants

Figure 22.19 Genetically engineered plants.

• Corn, soybean, and cotton plants are commonly genetically altered.

• In 2011, 94% of the soybeans and 80% of the corn planted in the United States had been genetically engineered.

22.3 DNA Technology

a. Herbicide-resistant soybean plants b. Nonresistant potato plant c. Pest-resistant potato plant


(all): Courtesy Monsanto

39


Transgenic plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Transgenic Crops of the Future

Improved Agricultural Traits

Disease-protected Wheat, corn, potatoes

Wheat, rice, sugar beets, canola Herbicide-resistant

Salt-tolerant

Drought-tolerant

Cold-tolerant

Improved yield

Modified wood pulp

Fatty acid/oil content

Protein/starch content

Amino acid content Corn, soybeans

Cereals, potatoes, soybeans, rice, corn

Corn, soybeans

Cereals, rice, sugarcane



Cereals, rice, corn, cotton

Trees

Improved Food Quality Traits

Salt-intolerant Salt-tolerant

b(both): Courtesy Eduardo Blumwald

Figure 22.20 Genetically engineered plants for desirable traits.

22.3 DNA Technology

40


Transgenic animals • Gene is inserted into the egg that when fertilized

will develop into a transgenic animal

• Current uses

– Gene pharming: production of pharmaceuticals in the milk of farm animals

– Larger animals: includes fish, cows, pigs, rabbits, and sheep

– Mouse models: the use of mice for various gene studies

– Xenotransplantation: pigs can express human proteins on their organs making it easier to transplant them into humans

22.3 DNA Technology

41

Production of a transgenic animal Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

human gene

for growth

hormone

human growth

hormone

development within a host goat

Transgenic goat produces

human growth hormone.

microinjection of human gene

milk

fusion of enucleated

eggs with 2n

transgenic nuclei donor of eggs

donor of egg

Cloned

transgenic

goats produce

human growth

hormone.

development within a host goat

milk Figure 22.21 Production

of a transgenic animal.

22.3 DNA Technology

42

What did we learn from the Human

Genome Project (HGP)?

• The human genome consists of about 3.4 billion bases and 23,000 genes.

• The human genome was sequenced in 2003.

• There are many polymorphisms, or small regions of DNA that vary among individuals identified.

• Genome size is not correlated with the number of genes or complexity of the organisms.

22.4 Genomics and Gene Therapy

43

What is the next step in the HGP?

• Functional genomics

• It helps us understand how the 23,000 genes

function.

• Genes make up less than 2% of the entire

human genome.

• Comparative genomics

• It helps understand how species have evolved.

• Comparing genomes may help identify base

sequences that cause human illness.

• It helps in our understanding of gene regulation.


44

Functional and comparative genomics

Figure 22.22 Functional and comparative genomics between chimpanzees and humans.



a (top): © Digital Vision/Getty RF; a (bottom): © Getty RF; b (left): © Digital Vision/GettyRF; b (right): © The McGraw-Hill

Companies, Inc. Bob Coyle, photographer; c (left): © Digital Vision/Getty RF; c (right): © Getty RF

a. b. c.

45

New endeavors

• Proteomics – the study of the structure, function, and interactions of cell proteins

• This can be difficult to study because

• protein concentrations differ greatly between cells.

• protein location and concentration interactions differ from minute to minute.

• understanding proteins may lead to the discovery of better drugs.

• Bioinformatics – the application of computer technologies to study the genome


46

How can we modify a person’s

genome?

• Gene therapy – insertion of genetic material

into human cells to treat a disorder

– In ex vivo therapy, cells are removed from the

body for treatment, and then reintroduced back

into the body.

– In in vivo therapy, the vector is introduced

directly into the body.

• Gene therapy has been most successful in

treating cancer.


47

Gene therapy

Figure 22.23 Gene therapy.



1. Remove bone

marrow stem cells.

defective gene

4. Return genetically

engineered cells

to patient.

normal gene

viral recombinant DNA

3.Viral recombinant

DNA carries normal

gene into genome.

reverse transcription

viral recombinant RNA

2. Use retroviruses

to bring the normal

gene into the bone

marrow stem cells.

normal gene

homologous

chromosomes

retrovirus

viral

recombinant

RNA

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Chapter 22 Lecture Outline - Napa Valley College · Chapter 22 Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes