21.1 - DNA and RNA Structure and...
Transcript of 21.1 - DNA and RNA Structure and...
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
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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
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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.
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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.
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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
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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.