copyright © 2010 pearson education, inc. chapter 8 genetically modified organisms gene...

Copyright © 2010 Pearson Education, Inc.

Chapter 8

Genetically Modified Organisms Gene Expression, Mutation, and Cloning


Chapter 8 Section 1

Protein Synthesis and Gene Expression

Part A: Transcription


Genetic Engineering

Genetic Engineering Alteration of hereditary traits by molecular

biological techniques One or more genes may be modified Genes may be moved from one organism to

another Move a gene that produces a desired

protein from one organism to another Alter regulation of gene expression

Change the amount of protein that a gene produces


Genetic Engineering

Genetic Engineering Controversy Benefits:

Potential to wipe out hunger by make crops more productive

Vaccinate children by eating foods Reduce heart problems by added omega-3

fatty acids to animals like pigs

Concerns: Is it ethical? Is it safe for use in food sources? Will it be used in humans?


8.1 Protein Synthesis and Expression

History of Genetic Engineering In the early 1980s, genetic engineers at

Monsanto® Company began producing recombinant bovine growth hormone (rBGH) Made by genetically engineered bacteria The bacteria were given DNA that carries

instructions for making BGH Giving growth hormone to cows increase

body size and milk production



How do genes make proteins?

Protein synthesis the process of using instructions carried on

a gene to create proteins. Gene – a sequence of DNA that encodes a

protein Protein – a large molecule composed of

amino acids

Several steps are involved and require both DNA and RNA.



Structure of DNA & RNA

DNA Double-stranded Each nucleotide

composed of deoxyribose, phosphate, and nitrogenous base

4 bases: adenine, thymine, guanine, cytosine



Structure of DNA & RNA

RNA Single-stranded Nucleotides

comprised of ribose, phosphate, and nitrogenous base

4 bases: A, C, G, and Uracil


8.1 Protein Synthesis and Expression:

From Gene to Protein

The flow of genetic information in a cell is DNA RNA protein

Figure 8.2



From Gene to Protein

There are 2 steps in going from gene to protein Transcription (DNA RNA) Translation (RNA Protein)


8.1 Protein Synthesis and Expression: Transcription

Transcription occurs in the nucleus. RNA polymerase binds to the promoter region

of the gene. RNA polymerase zips down the length of gene,

matching RNA nucleotides with complementary DNA nucleotides



The product of transcription is messenger RNA (mRNA).



Animation—TranscriptionPLAY


Chapter 8 Section 1


End Part A: Transcription


Chapter 8 Section 1


Part B: Translation and the Genetic Code


8.1 Protein Synthesis and Expression: Translation

Translation Uses mRNA template to make protein Translation occurs in the cytoplasm Translation requires:

mRNA amino acids ATP Ribosomes Transfer RNA (tRNA)



Ribosomes The ribosome is composed of

rRNA and comprises a small and a large subunit.

When subunits come together, mRNA can be threaded between them to make protein Also requires transfer RNA

(tRNA) to bring correct amino acids

Figure 8.4

Largesubunit

Smallsubunit



Transfer RNA (tRNA ) Each tRNA carries

one specific amino acids and matches its anticodon with codons on mRNA

So what are codons and anticodons??

Figure 8.5

Anticodon

mRNA

tRNA

Aminoacid

Binding site foramino acid

Region of internalcomplementarity

Codon



As ribosome moves along mRNA, small sequences of nucleic acids are exposed

Codon – a three letter genetic code of nucleic acids in mRNA that indicate a specific amino acid

Anticodon – a complementary three nucleic acid sequence on tRNA that matches codon

>By using anticodons to match codons, tRNA can bring the correct amino acid

Figure 8.5


8.1 Protein Synthesis and Expression: Genetic Code

The genetic code The use of nucleic acid codons to specify

amino acid sequence in proteins A codon is comprised of three nucleotides = 64

possible combinations (43 combinations) 61 codons code for ~20 amino acids

Redundancy – may be more than 1 code per amino acid

3 others are stop codons, which end protein synthesis


8.1 Protein Synthesis and Expression: Genetic Code

Table 8.1



A protein is put together one amino acid at a time.1. The ribosome attaches to the mRNA at the

promoter region.

2. Ribosome facilitates the docking of tRNA anticodons to mRNA codons.

3. When two tRNAs are adjacent, a bond is formed between their amino acids.



Figure 8.7

Amino acids and tRNAs float freely in the cytoplasm.

Enzymes facilitate the bind-ing of a specific tRNA to its appropriate amino acid.

Amino acid

tRNA

1

2

Translation Step by Step



A tRNA will dock if the complementary RNA codon is present on the ribosome.

The amino acids join together to form a polypeptide.

Ribosome

Stop codon

Amino acid chain (polypeptide)

ilepheala

UAUAAA

GCCUUUAUA

Figure 8.7

ser ala

val

AGU

arg

UCC

CGG

4

3



Figure 8.7

The ribosome moves on to the next codon to receive the next tRNA.

When the ribosome reaches the stop codon, no tRNA can base-pair with the codon on the mRNA. RNA and the newly synthesized protein are released.

Ribosome

Stop codon

Amino acid chain (polypeptide)

ilepheala

UAUAAA

GCCUUUAUA

CGG

arg

UCC

6

5



Figure 8.7

The chain of amino acids folds, and the protein is ready to perform its job.

The subunits of the ribosome separate but can reassemble and begin translation of another mRNA.

Protein(such as BGH)

AGC

CUCUCGUAA

STOPGAG

8

7



Animation—TranslationPLAY


Chapter 8 Section 1


END Part B: Translation and the Genetic Code


Chapter 8 Section 1


Part C: Types of Mutations and Regulating Gene Expression


8.1 Protein Synthesis and Expression: Mutations

Mutations = Changes in genetic sequence Changes in genetic sequence might affect

the order of amino acids in a protein. Protein function is dependent on the precise

order of amino acids


8.1 Protein Synthesis and Expression: Mutation

Figure 8.8

Possible outcomes of mutation: 1 - no change in protein (neutral mutation)2 - non-functional protein3 - different protein


8.1 Protein Synthesis and Expression: Mutation

Types of Mutations

1.Base-substitution mutation – simple substitution of one base for another

2.Frameshift mutation – addition or deletion of a base, which changes the reading frame



Figure 8.9

• Neutral Mutation

• Frameshift Mutation

- adding or deleting a nucleic acid

- shifts entire sequence

Examples of Mutations



Overview of Gene Expression Each cell in your body (except sperm and

egg cells) has the same DNA. But each cell only expresses a small

percentage of genes.


8.1 Protein Synthesis and Expression: An Overview of Gene Expression

Regulating gene expression Turning a gene or a set of genes on or off

EXP: Nerves and muscles have the same suite of genes, but express different genes.

Figure 8.11



Regulating gene expression 1. Repression of transcription

Figure 8.11



Regulating gene expression 2. Activation of transcription

Figure 8.11


Chapter 8 Section 1


Part C: Types of Mutations and Regulating Gene Expression


Chapter 8 Section 2

Producing Recombinant Proteins


8.2 Producing Recombinant Proteins:

Cloning a Gene Using Bacteria

Producing Recombinant Proteins BGH is a protein, and is coded by a

specific gene. Transfer of BGH gene to bacteria allows for

growth under ideal conditions. Bacteria can serve as “factories” for

production of BGH.


8.2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria

Two Important molecules in cloning

1.Restriction enzymes 2.Plasmids



Restriction enzymes Used by bacteria as a form of defense. Restriction enzymes cut DNA at specific

sequences. Leave “sticky ends”

They are important in biotechnology because they allow scientists to make precise cuts in DNA.



Plasmid Small, circular piece of bacterial DNA that exists

separate from the bacterial chromosome. Plasmids are important because they can act as

a ferry to carry a gene into a cell.

Copyright © 2010 Pearson Education, Inc. Figure 8.13

BGH gene is cut from the cow chromosomeusing restriction enzymes that leave “stickyends” with specific base sequences.

DNA

BGHgene

Cow cell

8.2 Producing Recombinant Proteins:

Steps in Cloning a Gene Using Bacteria Step 1. Remove the gene from the cow

chromosome using restriction enzymes

1



Step 2. Insert the BGH gene into the bacterial plasmid



Recombinant – Indicates material that has been genetically engineered. A gene that has been removed from its original genome and combined with another.

After step 2, the BGH is now referred to as recombinant BGH or rBGH.


The recombinant plasmid isreinserted into a bacterial cell.

The plasmids and the bacterial cellsreplicate, making millions of copies ofthe rBGH gene.

The rBGH genes produce largequantities of rBGH proteins that areharvested, purified, and injected intocows to increase milk production.

rBGHproteins

Recombinantplasmid


Step 3. Insert the recombinant plasmid into a bacterial cell

3


8.2 Producing Recombinant Proteins

Animation—Producing Bovine Growth HormonePLAY



Use of rBGH in Agriculture About 1/3 of cows in the US are injected

with rBGH. rBGH increases milk volume from cows by

about 20%. Increase profits for both ranchers and

industry



Controversy over Use of rBGH Controversy over safety to humans

USDA and Monsanto argue that milk from rBGH-treated cows is indistinguishable from non-treated.

Activists disagree.

Welfare of cows? Europe and Canada banned rBGH over concerns on the health of cows.



The same principles apply to other proteins Clotting proteins for hemophiliacs are

produced using similar methods. Insulin for diabetics is also produced in this

way.


END Chapter 8 Section 2

Producing Recombinant Proteins


Chapter 8 Section 3

Genetically Modified Foods


8.3 Genetically Modified Foods

Artificial Selection All agricultural products

are the result of genetic modification through selective breeding.

Artificial selection does not move genes from one organism to another, but does drastically change the characteristics of a population.

Figure 8.13


8.3 Genetically Modified Foods:

Why Genetically Modify Crop Plants? Increase shelf life, yield, or

nutritional value

Exp: Golden rice has been genetically engineered to produce beta-carotene, which increases the rice’s nutritional yield.

Figure 8.16


8.3 Genetically Modified Foods: Modifying Plants with the Ti Plasmid and Gene Gun

Modifying Plants Directly (Different than rBGH, which was a protein

injected into cows) In order to do this, the target gene must be

inserted into the plant cell. Two methods can inject genes into plants:

1. Ti plasmid

2. Gene gun



Modifying Plants wiith the Ti plasmid To modify the plant, must get gene across

cell wall The bacterium Agrobacterium tumefaciens

does this naturally, creating ‘galls’

• The bacterium can do this by using the Ti plasmid



Figure 8.17b

Modifying Plants wiith the Ti plasmid



The Gene Gun

Figure 8.18

Shock wavesGun

“Bullet”

Microscopicparticles coatedwith gene ofinterest are“shot” intoplant cells.

Plant cellsin culture



Transgenic organism the result is the incorporation of a gene

from one organism to the genome of another.

Also referred to as a Genetically Modified Organism (GMO).


8.3 Genetically Modified Foods: Effect of GM Crops and the Environment

Benefits Crops can be engineered for resistance to

pests, thus farmers can spray fewer chemicals.

Concerns GM crops may actually lead to increased

use of pesticides and herbicides. EXP: Roundup-Ready plants

GM crop plants may transfer genes to wild relatives.


End Chapter 8 Section 3

Genetically Modified Foods


Chapter 8 Section 4

Genetically Modified Humans


8.4 Genetically Modified Humans: Stem Cells

Stem cells: undifferentiated cells Totipotent = capable of

growing into many different kinds of cells and tissues.

Figure 8.20




Use of Stem cells Stem cells can be collected, with consent,

from left over embryos from artificial fertilization

Cells can be grown ‘in vitro’ in the lab Can be ‘directed’ to develop into many

different kinds of tissues



Therapeutic Cloning Stems cells might be used to treat

degenerative diseases Alzheimer’s or Parkinson’s, multiple

sclerosis, or liver, lung, or heart disease.

Stem cells could also be used to grow specific tissues to treat burns, heart attack damage,

replacement cartilage in joints, or spinal cord injuries.


8.4 Genetically Modified Humans:

Human Genome Project international effort to map the sequence of

the entire human genome (~20,000 – 25,000 genes). A genome is all of the genes in an organism For comparative purposes, genomes of

other model organisms (E. coli, yeast, fruit flies, mice) were also mapped.



Gene Therapy= replacement of defective genes with

functional genes

Two approaches:1.Germ line gene therapy

2.Somatic cell gene therapy


8.4 Genetically Modified Humans: Gene Therapy

Germ line gene therapy Embryonic treatment Embryo supplied with a functional version

of the defective gene. Embryo + cells produced by cell division

have a functional version of gene. Including their children

> would prevent genetic diseases



Somatic cell gene therapy fix or replace the defective protein only in

specific cells. Performed on adult body cells

Put copy of good gene into cells in lab, multiply cells, then introduce to affected person

Already used as a treatment of SCID (severe combined immunodeficiency)



Cloning Humans

Cloning = making a genetically identical organism Cloning occurs naturally whenever identical

twins are produced.

Cloning of offspring from adults has already been done with cattle, goats, mice, cats, pigs, and sheep. Cloning is achieved through the process of

NUCLEAR TRANSFER.



Cloning Dolly the Sheep


8.4 Genetically Modified Humans: Cloning Humans

Genetic engineering is controversial.

Table 8.2


END Chapter 8 Section 4



END Chapter 8

copyright © 2010 pearson education, inc. chapter 8 genetically modified organisms gene...

Documents