Download Pierce Genetics: A Conceptual Approach 3e

Benjamin A. Pierce
•GENETICS ESSENTIALS
•Concepts and Connections
• SECOND EDITION
CHAPTER 10
From DNA to Proteins: Transcription
and RNA Processing
© 2013 W. H. Freeman and Company
CHAPTER 10 OUTLINE
• 10.1 RNA, Consisting of a Single Strand of Ribonucleotides,
Participates in a Variety of Cellular Functions, 258
• 10.2 Transcription Is the Synthesis of an RNA Molecule from a DNA
Template, 260
• 10.3 The Process of Bacterial Transcription Consists of Initiation,
Elongation, and Termination, 264
• 10.4 Many Genes Have Complex Structures, 268
• 10.5 Many RNA Molecules Are Modified after Transcription in
Eukaryotes, 270
10.1 RNA, CONSISTING OF A SINGLE STRAND OF
RIBONUCLEOTIDES, PARTICIPATES IN A VARIETY
OF CELLULAR FUNCTIONS
• The structure of RNA
• Primary structure
• Secondary structure
10.1 RNA, Consisting of a Single Strand of
Ribonucleotides, Participates in a Variety of
Cellular Functions
• The structure of RNA
• Classes of RNA
•
•
•
•
Ribosomal RNA – rRNA
Messenger RNA – mRNA
Transfer RNA – tRNA
Small nuclear RNAs – snRNAs
• Small nuclear ribonucleoproteins – snRNPs
•
•
•
•
Small nuclear RNAs – snoRNAs
Small cytoplasmic RNAs – scRNAs
MicroRNAs – miRNAs
Small interfering RNAs – siRNAs
10.2 TRANSCRIPTION IS THE SYNTHESIS OF AN
RNA MOLECULE FROM A DNA TEMPLATE
• The template:
• The transcribed strand: template strand
10.2 TRANSCRIPTION IS THE SYNTHESIS OF AN
RNA MOLECULE FROM A DNA TEMPLATE
• The template:
• The transcription unit
• A promoter
• RNA-coding sequence
• Terminator
10.2 Transcription Is the Synthesis of an RNA
Molecule from a DNA Template
• The substrate for transcription:
• Ribonucleoside triphosphates – rNTPs added to the 3′ end of
the RNA molecule.
• The transcription apparatus:
• Bacterial RNA polymerase: five subunits made up of the core
enzyme:
• The sigma  factor: binding to the promoter when transcription
starts.
• Core enzyme +  factor = holoenzyme
10.2 Transcription Is the Synthesis of an RNA
Molecule from a DNA Template
• Initiation
• The substrate for transcription:
• Ribonucleoside triphosphates – rNTPs added to the 3′ end of the RNA
molecule.
• The transcription apparatus:
• Eukaryotic RNA polymerases
10.3 THE PROCESS OF BACTERIAL
TRANSCRIPTION CONSISTS OF INITIATION,
ELONGATION, AND TERMINATION
• Initiation
• Bacterial promoters:
• Consensus sequences: sequences that possess considerable
similarity.
• -10 consensus : 10 bp upstream of the start site.
• Pribnow box:
• 5 TATAAT 3
• 3 ATATTA 5
• - 35 consensus sequence: TTGAC
10.3 The Process of Bacterial
Transcription Consists of Initiation,
Elongation, and Termination
• Initiation
• Initial RNA synthesis: No primer is required.
• The location of the consensus sequence determines the position
of the start site. (next slide)
• Elongation
• RNA elongation is carried out by the action of RNA polymerase.
10.3 The Process of Bacterial
Transcription Consists of Initiation,
Elongation, and Termination
• Termination
• Rho-independent termination: hairpin structure formed by inverted
repeats, followed by a string of uracils.
• Rho-dependent termination
10.4 MANY GENES HAVE COMPLEX
STRUCTURES
Gene Organization
• The concept of colinearity and noncolinearity
GENE ORGANIZATION
• Introns
• Exons
THE CONCEPT OF THE GENE
• The gene includes DNA sequence that codes for
all exons, introns, and those sequences at the
beginning and end of the RNA that are not
translated into a protein, including the entire
transcription unit―the promoter, the RNA coding
sequence, and the terminator.
10.5 RNA MOLECULES
The structure of messenger RNA
•A mature mRNA contains 5′ untranslated region
(5′ UTR, or leader sequence)
• Shine–Dalgarno sequence in bacteria
•Protein-coding region
•3′ untranslated region
10.5 MANY RNA MOLECULES ARE MODIFIED
AFTER TRANSCRIPTION IN EUKARYOTES
The addition of the 5′ cap:
•
•
•
A nucleotide with 7-methylguanine; 5′-5′ bond is attached to
the 5′ end of the RNA.
The addition of the poly(A) tail:
•
50 ~ 250 adenine nucleotides are added to the 3′ end of the
mRNA.
10.5 MANY RNA MOLECULES ARE MODIFIED
AFTER TRANSCRIPTION IN EUKARYOTES
•
Alternative splicing:
THE COMPLETE PROCESS
THE STRUCTURE OF TRANSFER RNA
• Rare modified RNA nucleotide bases
• Ribothymine
• Pseudouridine
• Common secondary structure―the cloverleaf
structure
• Anticodon
THE STRUCTURE AND PROCESSING
OF RIBOSOMAL RNA
• Large ribosome subunit
• Small ribosome subunit
SMALL INTERFERING RNAs AND
MicroRNAs
• RNA interference: limits the
invasion of foreign genes and
censors the expression of
their own genes
• Types of small RNAs
• Processing and function of
microRNAs