The Structure and Function of DNA
CHAPTER 10
• Transcription (DNARNA)
• RNA Polymerase
•Processing of Eukaryotic RNA
•Translation (mRNAProtein)
• The
Three Types of RNA
• Codons and the Genetic Code
• Ribosomes
• Steps of Translation
•Mutation
Viruses: Genes in Small Packages
Central Dogma of Biology: How Shape and Form Are Dictated By DNA Genes
Genotype:
The genes
carried in a
cell for a
particular
trait
Phenotype:
The physical
expression of
genes for a
particular trait
A segment of
DNA (gene)
carries
specific coded
instructions
for the making
of a single
proteins.
Transcription: From DNA to RNA
•
In transcription,
–
Genetic information is transferred from DNA to RNA.
–
An RNA molecule is transcribed from a DNA template.
Transcription
In Eukaryotes, the mRNA is Edited Before Leaving the Nucleus
Figure 10.14
The Structure and Function of DNA
CHAPTER 10
• Transcription (DNARNA)
• RNA Polymerase
•Processing of Eukaryotic RNA
•Translation (mRNAProtein)
• The
Three Types of RNA
• Codons and the Genetic Code
• Ribosomes
• Steps of Translation
•Mutation and Mutagens
Viruses: Genes in Small Packages
3 Types of RNA – Each With a Different Job
Messenger RNA (mRNA)
Carries copy of gene information
to the ribosome to make protein
anticodon
Transfer RNA
(tRNA)
CUG
=
CUG
Carries amino acids to the ribosome for
linking; identified by anticodon “sign”
Ribosomal RNA (rRNA)
Part of the structure of
the ribosome; key
component in amino
acid linking machinery
The Structure and Function of DNA
CHAPTER 10
• Transcription (DNARNA)
• RNA Polymerase
•Processing of Eukaryotic RNA
•Translation (mRNAProtein)
• The
Three Types of RNA
• Codons and the Genetic Code
• Ribosomes
• Steps of Translation
•Mutation and Mutagens
Viruses: Genes in Small Packages
Anatomy of a Messenger RNA
Trailer
Leader
Figure 10.17
How Gene Instructions are Communicated
mRNA Codon Dictionary of the Genetic Code
Central Dogma: DNARNAProtein
DNA template strand:
CGTTTACGACCGGCCTTAGATCCTGACG
Transcription
mRNA:
GCAAAUGCUGGCCGGAAUCUAGGACUGC
Translation
Protein:
by RNA polymerase
by ribosome
Met - Leu - Ala - Gly - Ile
Figure 10.16a
Figure 10.16b
The Structure and Function of DNA
CHAPTER 10
• Transcription (DNARNA)
• RNA Polymerase
•Processing of Eukaryotic RNA
•Translation (mRNAProtein)
• The
Three Types of RNA
• Codons and the Genetic Code
• Ribosomes
• Steps of Translation
•Mutation and Mutagens
Viruses: Genes in Small Packages
Translation: The Process
• Translation is divided into three phases:
– Initiation
– Elongation
– Termination
Translation: Initiation
•
Events of Initiation
1. The messenger RNA binds to the small ribosomal subunit
2. The two subunits of the ribosome come together
3. The first amino acid with its attached tRNA
Translation: Elongation
•
Events of Elongation
–
1. The anticodon of an
incoming tRNA pairs with
the mRNA codon.
2. The ribosome catalyzes
a peptide bond to
form between amino
acids
3. A tRNA leaves the P
site of the ribosome
4. The ribosome moves
down the mRNA
(translocation)
Translation: Termination
•
Events of Termination
1. Elongation continues until
the ribosome reaches a
stop codon.
2. The two subunits of the
ribosome separate
3. The mRNA is released to
be used again
4. The finished polypeptide
(protein) folds up and
begins functioning
Figure 10.10
Review: DNA RNA Protein
• The flow of genetic information in a cell
The Structure and Function of DNA
CHAPTER 10
• Transcription (DNARNA)
• RNA Polymerase
•Processing of Eukaryotic RNA
•Translation (mRNAProtein)
• The
Three Types of RNA
• Codons and the Genetic Code
• Ribosomes
• Steps of Translation
• Mutation
• Viruses: Genes in Small Packages
Mutations
• A mutation
– Is any change in the nucleotide sequence of DNA
– Is a permanent, heritable change
• Mutations may result from
– Errors in DNA replication.
– Physical or chemical agents called mutagens.
• Although mutations are usually lethal,
– They are the source of the rich diversity of genes in the
living world.
– They contribute to the process of evolution by natural
selection.
Base Substitution (Point Mutation)
DNA base substitutions can cause: missense, run-on,
nonsense, and silent mutations in the resultant protein
Figure 10.21
Insertions or Deletions of DNA nucleotides
Insertion/Deletions cause frameshift mutations in the
protein (and often run-on mutations too)
Figure 10.22b
Types of Mutation
The Structure and Function of DNA
CHAPTER 10
• Transcription (DNARNA)
• RNA Polymerase
•Processing of Eukaryotic RNA
•Translation (mRNAProtein)
• The
Three Types of RNA
• Codons and the Genetic Code
• Ribosomes
• Steps of Translation
•Mutation and Mutagens
Viruses: Genes in Small Packages
Viruses: Genes in Packages
• Properties of Viruses
– They exhibit some, but not all, characteristics of
living organisms
– They are made of DNA or RNA surrounded by a
protein coating. Some also have envelopes outside
their protein coat
– They are incredibly small (< 1 um)
– They are obligate intracellular parasites
– They they can only attack a small range of cell
types (host specificity)
Viruses Come in Many Shapes
Helical
Polyhedral
Enveloped
QuickTime™ and a
decompressor
are needed to see this picture.
Complex
Bacterial Viruses Can Either Reproduce Immediately
or Hide Within The Host Cell and Emerge When the Host is Dying
Figure 10.26
Animal Viruses Often Have a Membranous Envelope with Protein Spikes
QuickTime™ and a
decompressor
are needed to see this picture.
The influenza virus carries specific “spikes” that make them infective
Spikes are classified by Hemagglutinin (H) and Neuraminidase (N) types
e.g. H1N1
Animal Virus Lifecycle
Simplified Viral Reproductive Cycle
Figure 10.29
HIV, the AIDS Virus
• HIV is a
retrovirus.
– A retrovirus is
an RNA virus
that
reproduces by
means of a
DNA
molecule.
– It copies its
RNA to DNA
using reverse
transcriptase.
HIV Reproductive Cycle
How Human Immunodeficiency Virus Attacks T White Blood Cells
Figure 10.30b
The Structure and Function of DNA
CHAPTER 10
• Transcription (DNARNA)
• RNA Polymerase
•Processing of Eukaryotic RNA
•Translation (mRNAProtein)
• The
Three Types of RNA
• Codons and the Genetic Code
• Ribosomes
• Steps of Translation
•Mutation
Viruses: Genes in Small Packages