21.1 - DNA and RNA Structure and Function

21.2 – Gene Expression

21.3 – Genomics

21.4 – DNA Technology

21.1 – DNA and RNA

Structure and Function

Deoxyribonucleic acid

Genetic material

Largely found in chromosomes

Located in the nucleus of a cell

Bases: Adenine (A), Cytosine (C),

Guanine (G), Thymine (T)

Replicate so that it can be transmitted to

the next generation

Store information

Undergo mutations that provide genetic

variability

Double helix Ladder structure:

supports are composed of sugar and phosphate molecules; rungs are complementary bases

Two strands that spiral each other

Each strand is a polynucleotide because it is composed of a series of nucleotides

Nucleotide –molecule composed of three subunits: phosphate, deoxyribose, nitrogen-containing base

Nitrogen containing bases: A, C, G, T

Each new cell gets an exact copy of DNA

process of copying a DNA helix

Double-stranded structure of DNA› each original strand

serves as template for formation of complementary strand

Semiconservative › each new DNA strand

has original strand and new strand

Mutation: permanent change in the sequence of bases

Ribonucleic acid

Made up of nucleotides containing the sugar ribose

Bases: Adenine (A), Cytosine (C), Guanine (G), Uracil (U)

Single-stranded

G

U

A

C

S

S

S

S

P

P

P

P

base isuracil insteadof thymine

one nucleotide

G

U

A

C

ribose

Messenger RNA› mRNA› Carries genetic information from DNA to the

ribosomes in the cytoplasm to make proteins Ribosomal RNA

› rRNA› forms the subunits of ribosomes› Makes proteins for cell

Transfer RNA› Transfers amino acids to the ribosomes; amino acids

are joined and forms a protein› 20 types of amino acids, so 20 tRNAs functioning in

the cell› Each tRNA carries only 1 type of amino acid

Nucleic acids

Composed of nucleotides

Sugar phosphate backbone

Four different types of bases

RNA:

Found in nucleus and cytoplasm

Helper to DNA

Sugar = ribose

Bases = A, U, C, G

Single-stranded

Can be translated (to give proteins)

DNA:

• Found in nucleus and mitochondria

• Genetic material

• Sugar = deoxyribose

• Bases = A, T, C, G

• Double-stranded

• Is transcribed (to give RNA)

• Made one of the most significant contributions to understanding the structure of DNA

• Nobel Prize – 1962 – not listed as a recipient because of her death

• Used X-ray diffraction to discover makeup of DNA

• Photographs of crystallized DNA showed that the linked sugar-phosphate strand in DNA were located on the outside of the molecule

• Discovered DNA helix had two separate strands

21.2 – Gene Expression

Proteins made of subunits called amino acids

20 different amino acids commonly found in

proteins

Proteins differ based on the number and order

of their amino acids

Some proteins are structural proteins and others are enzymes

Fun Fact:

The protein hemoglobin is responsible for blood’s red color

Enzymes are organic catalyst that speed

reactions in cells.

Ea Eb

A –> B –> C

Enzymes are specific to specific

1st step is transcription

› Strand of mRNA forms that’s complementary to

a portion of DNA. The molecule that forms is a

transcript of a gene. The mRNA strand then

goes to the ribosome for protein production

2nd step is translation

› Translation means to put information into a

different language

› Protein synthesis requires translation

› In this case a sequence of nucleotides is

translated into a sequence of amino acids

DN Adouble helix

DN A

transcriptionin nucleus

translationat ribosome

mRN A

codon 1 codon 2 codon 3

G

G

C

C

G

G

C

C

G

G

C

polypeptide N N NC C C C C

R1 R2 R3

arginine tyrosine tryptophan

O O O

G

C

G

C

G

C

C

G

A

U

T

A

A

T

T

A

U

T

G

C

G

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

4 bases› A,C,U,G

These 4 code for 20 amino acids

Triplet code

Each 3 letter unit of an mRNA molecule is called a codon

61 triplet correspond to a particular amino acid. The remaining 3 are stop codons

Methionine is also a start codon

Most amino acids have more than one codon

DNA serves as a template for the production of an RNA molecule

All classes of RNA are formed by transcription

› Focus on transcription to form mRNA

Starts with RNA polymerase opens the DNA helix, complementary base paring occurs. RNA polymerase joins the RNA nucleotides and an mRNA molecule results

› U replaces T

C

C G

A T

T

G

C

A

C

G

U

C

C

G

C

T A

C G

T A

A T

Transcription is taking placehere—mRNA nucleotides arebeing joined by the enzymeRNA polymerase so that theirsequence is complementaryto a strand of DNA.

RNApolymerase

DNAtemplatestrand

inactive DNAstrand

to mRNA processing

5

3

This mRNA transcript isready to be processedandthen it will move into thecytoplasm.

Go from RNA to Protein3 steps:

1. 1. Initiation: mRNA binds to the ribosome

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

Made of 3 RNA bases

Bases act as a code

for amino acids in

translation

Every 3 bases on the

mRNA is called a

codon that codes for

a particular amino

acid in translation

Second Base

UAAstop

U

C

A

G

U

C

A

G

U

C

A

G

U

C

A

G

U

C

A

G

U C A G

ThirdBase

FirstBase

UUUphenylalanine

UUCphenylalanine

UUAleucine

UUGleucine

CUUleucine

CUCleucine

CUAleucine

CUGleucine

AUUisoleucine

AUCisoleucine

AUAisoleucine

AUG (start)methionine

GUUvaline

GUCvaline

GUAvaline

GUGvaline

UCUserine

UCCserine

UCAserineUCG

serine

CCUproline

CCCproline

CCAproline

CCGproline

ACUthreonine

ACCthreonine

ACAthreonine

ACGthreonine

GCUalanine

GCCalanine

GCAalanine

GCGalanine

UAUtyrosine

UACtyrosine

UAGstop

CAUhistidine

CAChistidine

CAAglutamine

CAGglutamine

AAUasparagine

AACasparagine

AAAlysine

AAGlysine

GAUaspartate

GACaspartate

GAAglutamate

GAGglutamate

UGUcysteine

UGCcysteine

UGAstop

UGGtryptophan

CGUarginine

CGCarginine

CGAarginine

CGGarginine

AGUserine

AGCserine

AGAarginine

AGGarginine

GGUglycine

GGCglycine

GGAglycine

GGGglycine

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

Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

P siteA site

large ribosomalsubunit

met

C

G

U A

UA

polypeptide

amino acid

met

ala

tryp

ser

val asp

U

A

C A

UG G A C

C U G

polypeptide bondmet

ala

tryp

ser

val

asp

G A CU A A C C

C U G

thr

free polypeptidemet

ala

tryp

ser

val

asp

thr

2b. Second stage of elongation. Theribosome has moved to the rightand the tRNA-polypeptide at the P siteis now longer by one amino acid. One

tRN A is outgoing and another tRN Ais incoming.

2a. Elongation occurs in two stages.First stage of elongation.tRNA-polypeptide is at the Psite and a tRNA-amino acid is at theA site. The polypeptide will betransferred to the tRNA-amino acid.

smallribosomal

subunit

1. Initiation. The small ribosomal subunit,the mRNA, the first tRNA-amino acid,and the large ribosomal subunitcome together.

3. Termination. When the ribosomereaches a stop codon, all participantsseparate and the polypeptide isreleased.

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

There are 5 levels of gene regulation.

These are for the purposes of

processing and regulating proteins.

3 steps occur in the nucleus

2 steps occur in the cytoplasm, or

outside of the nucleus

5 Levels of Regulation

1) Pretranscriptional2)Transcriptional

3)posttranscriptional4)Transitional

5)Posttransitional

2) Transcriptional

Occurs in the

Nucleus

Controls which genes are

transcribed and speed it happens

at

Trying to form

mRNA

3) Posttranscriptional

Occurs in the

Nucleus

Controls the amount of mRNA needed for

protein synthesis

4) Transitional

Occurs in the

cytoplasm

Checks the mRNA before it can leave to

begin translation

5) Posttranslational

Occurs in the

cytoplasm

This stage checks to make sure the protein made is

necessary or if it needs to be terminated so as not to waste

any energy

Transcription

in

nucleus

Translation

at

Ribosome

Protein Synthesis occurs

1. DNA in nucleus

serves as a template

for mRNA.

2. mRN A is processed

before leaving the nucleus

3. mRNA moves into

cytoplasm and becomes

associated with ribosomes

4. tRNAs with

anticodons carry

amino acids

to mRNA.

5. Anticodon–codon

complementary

base pairing occurs

6. Polypeptide synthesis

takes place one amino

acid at a time.

21.3 – Genomics

•Human Genome Project (HGP)

–Took 13 years and gave researchers the order of 3 billion A, T, C, and G bases in our genome.

–Sperm DNA and white blood cells were used.

–Findings:•Genome size is not proportionate to the number of genes.•Less than 25,000 genes were found in the human genome.•After comparing that number to other organisms, it was reduced to 20,500 genes.•They did not find out exactly what human genes do yet.•There are instruments that can analyze up to 2 million base pairs of DNA within 24 hours.

Functional Genomics

› The study of how genes function and form

the human being together.

Comparative Genomics

› This can tell us how species have evolved

and how genes and noncoding regions

function.

Proteomics

› Study of structure, function, and interaction of cellular proteins.

› To understand a protein these need to be considered:

Concentration

Interactions

Cellular location

Chemical modifications

› This study is important to the discovery of creating better drugs.

Bioinformatics

› Use of computer technology to study genomes.

› Using these technologies, causes-and-effects can be discovered

•Ex Vivo

–Outside of the body

4. Return geneticallyengineered cellsto patient.

1. Remove bonemarrow stem cells.

2. Use retrovirusesto bring the normalgene into the bonemarrow stem cells.

3. Viral recombinantDNA carries normalgene into genome.

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

defective gene

viral recombinant DNA

reverse transcription

viral recombinant RNA

normal gene

retrovirus

viral recombinantRNA

normal gene

•In Vivo

–Inside the body

–Therapeutic or corrective DNA is directly injected into the body cells normally through the form of a virus.

–This has been used to cure cystic fibrosis and poor coronary circulation.

•Problems

–This type of therapy is experimental and not approved by FDA.

–It is not necessarily a safe and effective therapy

•Ex. A child developed leukemia like condition after therapy for severe combined immunodeficiency.

Gene Therapy Methods Cont.

21.4 – DNA Technology

Cloning-production of genetically identical

copies.

Can be whole genes or specific DNA

sequences

Recombinant DNA (rDNA) allows this. rDNA

contains DNA from two or more sources.

rDNA created through a vector (plasmid),

through which the target gene is

introduced to a host cell (bacterium).

•Polymerase Chain Reaction (PCR)•Can copy specific sequences less than one part in a million of the total of the DNA• Requires the use of DNA polymerase, the enzyme that carries out DNA replication. Also needs nucleotides for each new DNA strands. •Repeated replication of target strands.•Uses:

DNA fingerprinting

Genetic history

Restriction enzymecleaves DNA.

DNA ligase sealsthe insulin geneinto the plasmid.

Host cell takes uprecombined plasmid.

Gene cloning occurs. Bacteria produce a product.

Specific DNA Cloning

oldnew

new

new

old

old old

old

old old

new

new

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

Scientists can use genetic engineering to

create biotechnology products

› Transgenic Organisms

Major fields of biotechnology involved

with bacteria, plants and animals.

Benefits include production of

medicines, and increased/stabilized

food supply with the of transgenic plants

and animals.

Bacteria-

› Grown in bioreactors.

› Help to produce such products as insulin,

Hepatitis B vaccine, human growth hormone, and clotting agents

› “Oil-eating” bacteria and Frost-Plus/Minus

Bacteria on plants.

› Genetically engineered plants given

“suicide” genes to self-destruct once task is

accomplished

Plants› Engineered to be resistant to herbicides and

predatory insects.

› Engineered to grow better in salty soil and cold temperatures to increase yield.

› Some plants now genetically resistant to certain blights

› Also enhance the food quality. Add amino acids and proteins to corn, soybeans, rice and potatos.

Animals› Technology makes it

possible to insert genes into animals eggs.

› Microinjection- done by hand

› Vortex Mixing- Eggs placed in agitator with needles and DNA. Needles form small holes in eggs for DNA to pass through

› When eggs are fertilized, produce transgenic animals

› Produces larger healthier animals. We can augment them for specific purposes.

fusion of enucleatedeggs with 2ntransgenic nuclei

microinjection of human gene

donor of egg

human genefor growthhormone

development within a host goat

ransgenic goat produceshuman growth hormone.

donor of eggs

Clonedtransgenicgoats producehuman growthhormone.milk

development within a host goat

human growth

hormone

› Use of transgenic animals to create

pharmaceuticals.

› Therapeutic genes encoded into livestock’s DNA

through microinjection. In vitro fertalization helps

to produce offspring.

› The therapeutic proteins show up in the milk and

offspring of the livestock.

› These offspring can then be cloned.

› Potential Uses:

Treatment of cystic fibrosis, cancer, numerous

blood diseases

Proponents argue it is answer to world

hunger and could eliminate pesticide

use.

Opponents say there is not enough

evidence to back claims of safety.

Inconclusive evidence for either case at

this time.

As of 2008: 80% of US corn genetically

modified.