Ce diaporama a bien été signalé.
Nous utilisons votre profil LinkedIn et vos données d’activité pour vous proposer des publicités personnalisées et pertinentes. Vous pouvez changer vos préférences de publicités à tout moment.
RNA & Protein Synthesis
Uracil
Hydrogen bonds
Adenine
Ribose
RNA
Basic components of RNA
 Ribonucleic acid
consists of following
basic components
 1- Ribose sugar
 2- Phosphate in
dies...
Primary structure of RNA
 Although there are
multiple types of RNA
molecules, the basic
structure of all RNA is
similar.
...
Secondary structure of RNA
 Single-stranded RNA can
also form many
secondary structures in
which a single RNA
molecule fo...
DNA can replicate or
undergo transcription
 Replication-it is process by which DNA copies itself
to produce identical dau...
DNA RNA
Structure Double
Stranded
Single Stranded
Bases- Purines Adenine (A) Adenine (A)
Guanine (G) Guanine (G)
Bases -
P...
Types of RNA
1) messenger RNA (mRNA)- carries
instructions from the DNA in the
nucleus to the ribosome
Types of RNA
2) ribosomal RNA (rRNA)-
combines with proteins to
form the ribosome (proteins
made here)
3) transfer RNA (tR...
Types of RNA
 4 ) snRNA – small nuclear RNA
 5) snoRNA- small nucleolar RNA
 6) scRNA- small cytoplasmic RNA
 7) micro...
Protein Synthesis Overview
There are two steps to making
proteins (protein synthesis):
1) Transcription (nucleus)
DNA RNA...
 DNA
 Transcription
 RNA
 Translation
 Protein
 Conventional concept
 Genome
 Transcription
 Transcriptome
 Tran...
Proteins.
 Everything a cell is or does depends on the
proteins it contains.
From genes to proteins.
 Two steps – Transcription , Translation.
Transcription
RNA
DNA
RNA
polymerase
Adenine (DNA and RNA)
Cytosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
...
TRANSCRIPTION
 It is a process by which RNA is synthesize from
DNA. The genetic information stored in DNA is
expressed th...
Transcription
RNA Editing: Before the mRNA leaves the
nucleus, it is called pre-mRNA or (hnRNA)
heterogeneous nuclear RNA ...
Transcription
1) Transcription begins when the
enzyme RNA polymerase binds to
DNA at a promoter region.
Promoters are sign...
Transcription
3) RNA polymerase pairs up free
floating RNA nucleotides with
DNA template and joins the
nucleotides togethe...
Steps of transcription
 Initiation
 Elongation
 Termination
 post – transcriptional modifications
 The RNAs produced ...
Cell
Nucleus
Cell
Nucleus
Nucleus
Chromosome
Key
= Phosphate
= Sugar
= Uracil
= Adenine
= Guanine
= Cytosine
RNA
Polymerase
3’ 5’
Key
= Phosphate
= Sugar
= Uracil
= Adenine
= Guanine
= Cytosine
RNA
Polymerase
3’ 5’
Key
= Phosphate
= Sugar
= Uracil
= Adenine
= Guanine
= Cytosine
RNA
Polymerase
3’ 5’
Key
= Phosphate
= Sugar
= Uracil
= Adenine
= Guanine
= Cytosine
RNA
Polymerase =
3’ 5’
Key
= Phosphate
= Sugar
= Uracil
= Adenine
= Guanine
= Cytosine
RNA
Polymerase =
3’ 5’
Key
= Phosphate
= Sugar
= Uracil
= Adenine
= Guanine
= Cytosine
RNA
Polymerase =
3’ 5’
mRNA Strand =
Key
= Phosphate
= Sugar
= Uracil
= Adenine
= Guanine
= Cytosine
RNA
Polymerase =mRNA Strand =
3’ 5’
On average rate of RNA
synthesis is about 43
nucleotides per second .
TRANSCRIPTION-COMPLIMENTARY BASE
PAIR RELATIONSHIP
 DNA 5’ A T G C A T G G C A 3’ CODING STRAND
 3’ T A C G T A C C G T ...
The conventional numbering system of promoters
Bases preceding
this are numbered
in a negative
direction
There is no base
...
Promoter sites
 In eukaryotes promoter DNA bases sequences known as HOGNESS BOX or
TATA BOX located on the left about 25 ...
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
 Eukaryotic promoter sequences...
 Factors that control gene expression can be divided
into two types, based on their “location”
 cis-acting elements
 DN...
Signals the end of
protein synthesis
Usually
an
adenine
 The core promoter is relatively short
 It consists of the TATA box
 Important in determining the pr...
 Regulatory elements affect the binding of RNA polymerase
to the promoter
 They are of two types
 Enhancers
 Stimulate...
RNA polymerases
 RNA polymerase I- synthesis of precursors of large
ribosomal RNAs.
 RNA polymerases II- synthesizes the...
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
 Three categories of proteins ...
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
A closed
complex
Released
after the
open
complex
is formed
RNA poly II can
now proceed to
the elongation
stage
12-23
Figure 12.7
12-26
Similar to the
synthesis of DNA
via DNA polymerase
Figure 12.8
On average, the rate of
RNA synthesis is about 43
nuc...
‘promoter’ Protein coding
Difference in gene structure between
- prokaryote
- eukaryote
core
‘promoter’
An important diffe...
Pre-mRNA
Transcription start, elongation, termination and RNA
processing in eukaryotes
: coding protein
: non-coding prote...
TERMINATION
 Transcription stops by termination signals. Two
types of termination identified.
 Rho depended- specific pr...
 coding sequences, called exons, are interrupted by
intervening sequences or introns
 Transcription produces the entire ...
 Aside from splicing, RNA transcripts can be modified
in several ways
 For example
 Trimming of rRNA and tRNA transcrip...
RNA Editing
 Introns are removed and extrons are spliced
 The spliceosome is a large complex that splices
pre-mRNA
 It is composed of several subunits known as
snRNPs (pronounce...
 The subunits of a spliceosome carry out several
functions
 1. Bind to an intron sequence and precisely recognize
the in...
Intron loops out and
exons brought closer
together
Intron will be degraded and
the snRNPs used again
 One benefit of genes with introns is a phenomenon
called alternative splicing
 A pre-mRNA with multiple introns can be ...
 The biological advantage of alternative splicing is
that two (or more) polypeptides can be derived
from a single gene
 ...
 Most mature mRNAs have a 7-methyl guanosine
covalently attached at their 5’ end
 This event is known as capping
 Cappi...
 The 7-methylguanosine cap structure is recognized
by cap-binding proteins
 Cap-binding proteins play roles in the
 Mov...
 Most mature mRNAs have a string of adenine
nucleotides at their 3’ ends
 This is termed the polyA tail
 The polyA tail...
Cell
Nucleus
Cell
Nucle
RNA
Polymerase
RNA Polymerase binds and unwinds
the DNA double helix.
RNA Polymerase binds and unwinds
the DNA double helix.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
RNA Polymerase binds and
unwinds the DNA double helix.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
RNA Polymerase binds and
unwinds the DNA double
helix.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
RNA Polymerase binds and
unwinds the DNA double
helix.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
RNA Polymerase binds and
unwinds the DNA double
helix.
RNA
Polymerase
RNA Polymerase binds and
unwinds the DNA double
helix.
RNA
Polymerase
RNA Polymerase binds to
the promoter region.
RNA
Polymerase
RNA Polymerase binds to
the promoter region.
RNA
Polymerase
RNA Polymerase binds to
the promoter region.
RNA
Polymerase
RNA Polymerase binds to
the promoter region.
RNA
Polymerase
RNA Polymerase binds to
the promoter region.
RNA
Polymerase
RNA Polymerase binds to
the promoter region.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymerase
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Cod...
RNA Polymerase reads the DNA
and creates the mRNA strand.
RNA
Polymeras
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Codo...
mRNA leaves the nucleus and enters
the cytoplasm.
RNA
Polymeras
Guanine
Cytosine
Thymine
Adenine
Uracil
Start Codon Stop C...
mRNA leaves the nucleus and enters
the cytoplasm.
mRNA leaves the nucleus and enters
the cytoplasm.
Nuclear Por
mRNA leaves the nucleus and enters
the cytoplasm.
Nuclear Por
mRNA leaves the nucleus and enters
the cytoplasm.
Nuclear Por
mRNA leaves the nucleus and enters
the cytoplasm.
Nuclear Por
mRNA leaves the nucleus and enters
the cytoplasm.
Nuclear Por
mRNA leaves the nucleus and enters
the cytoplasm.
Nuclear Por
mRNA leaves the nucleus and enters
the cytoplasm.
The Genetic Code
Proteins (polypeptides) are long chains of amino acids that
are joined together.
There are 20 different a...
AMINO ACIDS
 Amino acids are organic solvents.
 Have two functional groups –NH₂ and
-COOH group.
 The amino group is ba...
Semi-essential aminoacids.
These include Arginine and
Histidine.These are growth
promoting factors since they are not
syn...
The Genetic Code
A codon consists of three
consecutive nucleotides
that specify a single
amino acid that is to be
added to...
The
Codon
Table
 Sixty-four
combinations are
possible when a
sequence of
three bases are
used; thus, 64
different mRNA
co...
 Some codons do
not code for
amino acids; they
provide
instructions for
making the
protein.
 More than one
codon can cod...
All organisms use the same genetic
code (A,T,C,G).
This provides evidence that all
life on Earth evolved from a
common o...
Cracking the Code
 This picture shows the amino
acid to which each of the 64
possible codons corresponds.
 To decode a c...
Translation
Translation takes place
on ribosomes, in the
cytoplasm.
 The cell uses information
from messenger RNA
(mRNA) ...
Stapes of protein synthesis
 1) requirements of the components- amino
acids, ribosome, mRNA,tRNA, ATP
 2)activation of a...
Source:
http://www.coolschool.ca/lor/BI12/unit6/U06L01.htm
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Cytoplasm
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Amino
AcidtRNA
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Amino
AcidtRNA
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Amino
AcidtRNA
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Amino
AcidtRNA
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Amino
AcidtRNA
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Poly...
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Start Codon Codon Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Poly...
Key
= Uracil
= Adenine
= Guanine
= Cytosine
tart Codon Codon Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Polyp...
Key
= Uracil
= Adenine
= Guanine
= Cytosine
odon Codon Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Polypeptide...
Key
= Uracil
= Adenine
= Guanine
= Cytosine
n Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Polypeptide Chain
Pe...
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Codon Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Polypeptide Chain
Pept...
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Codon Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Polypeptide Chain
Peptide Bo...
Key
= Uracil
= Adenine
= Guanine
= Cytosine
on Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Polypeptide Chain
Peptide Bond
Key
= Uracil
= Adenine
= Guanine
= Cytosine
on Stop Codon
Ribosome
Anticodo
Amino
AcidtRNA
Polypeptide Chain
Peptide Bond
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Ribosome
Anticodo
Amino
AcidtRNA
Polypeptide Chain
Peptide Bond
Amino Acid Cha...
Key
= Uracil
= Adenine
= Guanine
= Cytosine
Ribosome
Anticodo
Amino
AcidtRNA
Polypeptide Chain
Peptide Bond
Final Protein ...
translation
 Initiation codon
AUG
 Termination codons or
non-sense codons or stop
signals
UAA
UAG
UGA
Messenger RNA (mRNA)
1) The mRNA that was transcribed from DNA
during transcription, leaves the cell’s nucleus and
enters ...
Transfer RNA(tRNA)
2) The mRNA enters the cytoplasm and attaches to a ribosome at the
AUG, which is the start codon. This ...
The Polypeptide “Assembly Line”
5) The ribosome moves along the mRNA and adds more amino
acids to the growing polypeptide ...
Completing the Polypeptide
6) The process continues
until the ribosome
reaches one of the three
stop codons on the
mRNA, a...
mRNA binds to the ribosome and
the code is read.
mRNA binds to the ribosome and
the code is read.
tRNA has the anticodon and amino
acid attaches.
Guanine
Cytosine Adenine
Uracil
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
Thr
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
ThrGlu
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
ThrGluThr
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
ThrGluThrAsp
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
ThrGluThrAspCys
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
ThrGluThrAspCysLeu
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
ThrGluThrAspCysLeuThr
Amino acids bind to each other
through peptide bonds.
Guanine
Cytosine Adenine
Uracil
ThrGluThrAspCysLeuThrSTOP
Ribosome hits the stop codon, and
protein synthesis is complete.
Guanine
Cytosine Adenine
Uracil
ThrGluThrAspCysLeuThrAsp
...
Ribosome hits the stop codon, and
protein synthesis is complete.
Guanine
Cytosine Adenine
Uracil
ThrGluThrAspCysLeuThrAsp
...
Ribosome hits the stop codon, and
protein synthesis is complete.
Guanine
Cytosine Adenine
Uracil
ThrGluThrAspCysLeuThrAsp
...
Amino acid chain coils into a
complete protein.
Amino acid chain coils into a
complete protein.
Source: http://www.biochem.arizona.edu/classes/bioc471/pages/Lecture1/Lecture1.html
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
RNA and Protein Synthesis
Prochain SlideShare
Chargement dans…5
×

RNA and Protein Synthesis

1 804 vues

Publié le

Publié dans : Technologie
  • Soyez le premier à commenter

RNA and Protein Synthesis

  1. 1. RNA & Protein Synthesis Uracil Hydrogen bonds Adenine Ribose RNA
  2. 2. Basic components of RNA  Ribonucleic acid consists of following basic components  1- Ribose sugar  2- Phosphate in diester linkage  4-Nitrogenous base pairs-  Purines- adenine, guanine  Pyrimidines- cytocine, uracil
  3. 3. Primary structure of RNA  Although there are multiple types of RNA molecules, the basic structure of all RNA is similar.  Each kind of RNA is a polymeric molecule made by stringing together individual ribonucleotides, always by adding the 5'-phosphate group of one nucleotide onto the 3'-hydroxyl group of the previous
  4. 4. Secondary structure of RNA  Single-stranded RNA can also form many secondary structures in which a single RNA molecule folds over and forms hairpin loops, stabilized by intramolecular hydrogen bonds between complementary bases.  Such base-pairing of RNA is critical for many RNA functions, such as the ability of tRNA to bind to the correct sequence of mRNA during translation
  5. 5. DNA can replicate or undergo transcription  Replication-it is process by which DNA copies itself to produce identical daughter molecules of DNA. DNA is the reserve bank of genetic information.  Transcription-transcription results in the formation of one single-stranded RNA molecule.
  6. 6. DNA RNA Structure Double Stranded Single Stranded Bases- Purines Adenine (A) Adenine (A) Guanine (G) Guanine (G) Bases - Pyrimidines Cytosine (C) Cytosine (C) Thymine (T) Uracil (U) Sugar Deoxyribose Ribose Differences between DNA and RNA: RNA’s JOB= Make Proteins!!
  7. 7. Types of RNA 1) messenger RNA (mRNA)- carries instructions from the DNA in the nucleus to the ribosome
  8. 8. Types of RNA 2) ribosomal RNA (rRNA)- combines with proteins to form the ribosome (proteins made here) 3) transfer RNA (tRNA)- transfers each amino acid to the ribosome as it is specified by coded messages in mRNA during the construction of a protein
  9. 9. Types of RNA  4 ) snRNA – small nuclear RNA  5) snoRNA- small nucleolar RNA  6) scRNA- small cytoplasmic RNA  7) micro- RNAs,miRNA, small interfering RNAs  Present in eukaryotes only.
  10. 10. Protein Synthesis Overview There are two steps to making proteins (protein synthesis): 1) Transcription (nucleus) DNA RNA 2) Translation (cytoplasm) RNA  protein
  11. 11.  DNA  Transcription  RNA  Translation  Protein  Conventional concept  Genome  Transcription  Transcriptome  Translation  Proteome  Current concept, Bioinformatics era
  12. 12. Proteins.  Everything a cell is or does depends on the proteins it contains.
  13. 13. From genes to proteins.  Two steps – Transcription , Translation.
  14. 14. Transcription RNA DNA RNA polymerase Adenine (DNA and RNA) Cytosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) Nucleus
  15. 15. TRANSCRIPTION  It is a process by which RNA is synthesize from DNA. The genetic information stored in DNA is expressed through RNA.  One of the two strands of DNA serves as Template and produces working copies of RNA molecules. The other DNA strand which does not participate in in transcription is referred to as coding strand or sense strand or non-template strand.
  16. 16. Transcription RNA Editing: Before the mRNA leaves the nucleus, it is called pre-mRNA or (hnRNA) heterogeneous nuclear RNA and it gets “edited.” Parts of the pre-mRNA that are not involved in coding for proteins are called introns and are cut out. The remaining mRNA pieces are called exons (because they are expressed) and are spliced back together to form the mRNA. Then the final mRNA leaves the nucleus through the nuclear pores and enters the cytoplasm headed to the ribosome.
  17. 17. Transcription 1) Transcription begins when the enzyme RNA polymerase binds to DNA at a promoter region. Promoters are signals in DNA that indicate to the enzyme where to bind to make RNA. 2) The enzyme separates the DNA strands by breaking the hydrogen bonds, and then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA.
  18. 18. Transcription 3) RNA polymerase pairs up free floating RNA nucleotides with DNA template and joins the nucleotides together to form the backbone of the new mRNA strand. 4) When mRNA hits a termination sequence, it separates from the DNA
  19. 19. Steps of transcription  Initiation  Elongation  Termination  post – transcriptional modifications  The RNAs produced during transcription are called primary mRNA transcripts. They undergo many alterations- terminal base additions, base modifications, splicing etc. This process is required to convert RNA into active form. Enzyme involved mainly is - ribonucleases.
  20. 20. Cell Nucleus
  21. 21. Cell Nucleus
  22. 22. Nucleus Chromosome
  23. 23. Key = Phosphate = Sugar = Uracil = Adenine = Guanine = Cytosine RNA Polymerase 3’ 5’
  24. 24. Key = Phosphate = Sugar = Uracil = Adenine = Guanine = Cytosine RNA Polymerase 3’ 5’
  25. 25. Key = Phosphate = Sugar = Uracil = Adenine = Guanine = Cytosine RNA Polymerase 3’ 5’
  26. 26. Key = Phosphate = Sugar = Uracil = Adenine = Guanine = Cytosine RNA Polymerase = 3’ 5’
  27. 27. Key = Phosphate = Sugar = Uracil = Adenine = Guanine = Cytosine RNA Polymerase = 3’ 5’
  28. 28. Key = Phosphate = Sugar = Uracil = Adenine = Guanine = Cytosine RNA Polymerase = 3’ 5’ mRNA Strand =
  29. 29. Key = Phosphate = Sugar = Uracil = Adenine = Guanine = Cytosine RNA Polymerase =mRNA Strand = 3’ 5’
  30. 30. On average rate of RNA synthesis is about 43 nucleotides per second .
  31. 31. TRANSCRIPTION-COMPLIMENTARY BASE PAIR RELATIONSHIP  DNA 5’ A T G C A T G G C A 3’ CODING STRAND  3’ T A C G T A C C G T 5’ TEMPLATE STRAND  RNA 5’ …....A U G C A U G G C A………3’
  32. 32. The conventional numbering system of promoters Bases preceding this are numbered in a negative direction There is no base numbered 0 Bases to the right are numbered in a positive direction Most of the promoter region is labeled with negative numbers
  33. 33. Promoter sites  In eukaryotes promoter DNA bases sequences known as HOGNESS BOX or TATA BOX located on the left about 25 nucleotides away(upstream) from the starting site of mRNA synthesis. Second site of recognition between 70 to 80 nucleotides upstream known as CAAT BOX.  Coding strand 5’ GGCCAATC ATATAA 3’  Template strand 3’ 5’  -70 bases -25 bases (coding region)  Start of transcription
  34. 34. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display  Eukaryotic promoter sequences are more variable and often much more complex than those of bacteria  For structural genes, at least three features are found in most promoters  Regulatory elements  TATA box (present in ~20 % of our genes) and other short sequences in TATA-promoters that have a similar function  Transcriptional start site Sequences of Eukaryotic Structural Genes
  35. 35.  Factors that control gene expression can be divided into two types, based on their “location”  cis-acting elements  DNA sequences that exert their effect only over a particular gene  Example: TATA box  trans-acting elements  Regulatory proteins that bind to such DNA sequences Sequences of Eukaryotic Structural Genes
  36. 36. Signals the end of protein synthesis
  37. 37. Usually an adenine  The core promoter is relatively short  It consists of the TATA box  Important in determining the precise start point for transcription  The core promoter by itself produces a low level of transcription  This is termed basal transcription
  38. 38.  Regulatory elements affect the binding of RNA polymerase to the promoter  They are of two types  Enhancers  Stimulate transcription  Silencers  Inhibit transcription  They vary widely in their locations, from –50 to –100 region
  39. 39. RNA polymerases  RNA polymerase I- synthesis of precursors of large ribosomal RNAs.  RNA polymerases II- synthesizes the precursors for mRNAs and small rRNAs.  RNA polymerases III- formation of tRNAs and small rRNAs.
  40. 40. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display  Three categories of proteins are required for basal transcription to occur at the promoter  RNA polymerase II  six different proteins called general transcription factors (GTFs or TFs) . They are- TFIID, TFIIA,TFIIB,TFIIF,TFIIE, TFIIH.  A protein complex called mediator. RNA Polymerase II and its Transcription Factors
  41. 41. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
  42. 42. A closed complex Released after the open complex is formed RNA poly II can now proceed to the elongation stage
  43. 43. 12-23 Figure 12.7
  44. 44. 12-26 Similar to the synthesis of DNA via DNA polymerase Figure 12.8 On average, the rate of RNA synthesis is about 43 nucleotides per second!
  45. 45. ‘promoter’ Protein coding Difference in gene structure between - prokaryote - eukaryote core ‘promoter’ An important difference between prokaryotes and eukaryotes is that eukaryotes’ genes are not split into intons and exons. In eukaryotes is the DNA coding protein are, Therefore, exons eventually end up in the mRNA intron exons
  46. 46. Pre-mRNA Transcription start, elongation, termination and RNA processing in eukaryotes : coding protein : non-coding protein: ‘leader’ and ‘trailer’ CAP CAP (poly A tail) The longest gene in human genome is more than 1.500.000 base pares (bp) and the mRNA is ~ 7000 nt. ‘promoter’ intron exons GENE mRNA AAAAAAAAAAA
  47. 47. TERMINATION  Transcription stops by termination signals. Two types of termination identified.  Rho depended- specific protein Rho factor, binds to the growing RNA, acts as ATPase and terminates transcription and releases RNA.  Rho independent – formation of hairpins of newly synthesized RNA.this occurs due to presence of palindromes. It is word that reads alike forward and backwards, like madam, motor. Presence of palindromes in DNA base sequence work as termination zone. Newly synthesize RNA folds to form hairpins due to complimentary base pairing, and termination occurs.
  48. 48.  coding sequences, called exons, are interrupted by intervening sequences or introns  Transcription produces the entire gene product  Introns are later removed or excised  Exons are connected together or spliced  This phenomenon is termed RNA splicing  It is a common genetic phenomenon in eukaryotes  Occurs occasionally in bacteria as well post transcriptional RNA modification
  49. 49.  Aside from splicing, RNA transcripts can be modified in several ways  For example  Trimming of rRNA and tRNA transcripts  5’ Capping and 3’ polyA tailing of mRNA transcripts y RNA MODIFICATION
  50. 50. RNA Editing
  51. 51.  Introns are removed and extrons are spliced
  52. 52.  The spliceosome is a large complex that splices pre-mRNA  It is composed of several subunits known as snRNPs (pronounced “snurps”)  Each snRNP contains small nuclear RNA and a set of proteins. Or small nuclear ribonucloprotein particle. Types of snRNPs are U1,U2,U3,U4,U5,U6. Pre-mRNA Splicing
  53. 53.  The subunits of a spliceosome carry out several functions  1. Bind to an intron sequence and precisely recognize the intron-exon boundaries  2. Hold the pre-mRNA in the correct configuration  3. Catalyze the chemical reactions that remove introns and covalently link exons Pre-mRNA Splicing
  54. 54. Intron loops out and exons brought closer together
  55. 55. Intron will be degraded and the snRNPs used again
  56. 56.  One benefit of genes with introns is a phenomenon called alternative splicing  A pre-mRNA with multiple introns can be spliced in different ways  This will generate mature mRNAs with different combinations of exons  This variation in splicing can occur in different cell types or during different stages of development Intron Advantage?
  57. 57.  The biological advantage of alternative splicing is that two (or more) polypeptides can be derived from a single gene  This allows an organism to carry fewer genes in its genome Intron Advantage?
  58. 58.  Most mature mRNAs have a 7-methyl guanosine covalently attached at their 5’ end  This event is known as capping  Capping occurs as the pre-mRNA is being synthesized by RNA pol II  Usually when the transcript is only 20 to 25 bases long Capping: marking 5’ends of mRNAs
  59. 59.  The 7-methylguanosine cap structure is recognized by cap-binding proteins  Cap-binding proteins play roles in the  Movement of some RNAs into the cytoplasm  Early stages of translation  Splicing of introns Function of Capping
  60. 60.  Most mature mRNAs have a string of adenine nucleotides at their 3’ ends  This is termed the polyA tail  The polyA tail is not encoded in the gene sequence  It is added enzymatically after the gene is completely transcribed The 3’ end of a mRNA: Tailing
  61. 61. Cell Nucleus
  62. 62. Cell Nucle
  63. 63. RNA Polymerase RNA Polymerase binds and unwinds the DNA double helix.
  64. 64. RNA Polymerase binds and unwinds the DNA double helix. RNA Polymerase Guanine Cytosine Thymine Adenine
  65. 65. RNA Polymerase binds and unwinds the DNA double helix. RNA Polymerase Guanine Cytosine Thymine Adenine
  66. 66. RNA Polymerase binds and unwinds the DNA double helix. RNA Polymerase Guanine Cytosine Thymine Adenine
  67. 67. RNA Polymerase binds and unwinds the DNA double helix. RNA Polymerase Guanine Cytosine Thymine Adenine
  68. 68. RNA Polymerase binds and unwinds the DNA double helix. RNA Polymerase
  69. 69. RNA Polymerase binds and unwinds the DNA double helix. RNA Polymerase
  70. 70. RNA Polymerase binds to the promoter region. RNA Polymerase
  71. 71. RNA Polymerase binds to the promoter region. RNA Polymerase
  72. 72. RNA Polymerase binds to the promoter region. RNA Polymerase
  73. 73. RNA Polymerase binds to the promoter region. RNA Polymerase
  74. 74. RNA Polymerase binds to the promoter region. RNA Polymerase
  75. 75. RNA Polymerase binds to the promoter region. RNA Polymerase Guanine Cytosine Thymine Adenine
  76. 76. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region
  77. 77. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  78. 78. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  79. 79. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  80. 80. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  81. 81. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  82. 82. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  83. 83. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  84. 84. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  85. 85. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymerase Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  86. 86. RNA Polymerase reads the DNA and creates the mRNA strand. RNA Polymeras Guanine Cytosine Thymine Adenine Uracil Start Codon Coding Region mRNA Strand
  87. 87. mRNA leaves the nucleus and enters the cytoplasm. RNA Polymeras Guanine Cytosine Thymine Adenine Uracil Start Codon Stop CodonCoding Region mRNA Strand Termination Sequ
  88. 88. mRNA leaves the nucleus and enters the cytoplasm.
  89. 89. mRNA leaves the nucleus and enters the cytoplasm. Nuclear Por
  90. 90. mRNA leaves the nucleus and enters the cytoplasm. Nuclear Por
  91. 91. mRNA leaves the nucleus and enters the cytoplasm. Nuclear Por
  92. 92. mRNA leaves the nucleus and enters the cytoplasm. Nuclear Por
  93. 93. mRNA leaves the nucleus and enters the cytoplasm. Nuclear Por
  94. 94. mRNA leaves the nucleus and enters the cytoplasm. Nuclear Por
  95. 95. mRNA leaves the nucleus and enters the cytoplasm.
  96. 96. The Genetic Code Proteins (polypeptides) are long chains of amino acids that are joined together. There are 20 different amino acids. The structure and function of proteins are determined by the order in which different amino acids are joined together to produce them. The four bases (letters) of mRNA (A, U, G, and C) are read three letters at a time (and translated) to determine the order in which amino acids are added to a protein.
  97. 97. AMINO ACIDS  Amino acids are organic solvents.  Have two functional groups –NH₂ and -COOH group.  The amino group is basic while carboxylic group is acidic in nature.  Soluble in water but insoluble in organic solvents e.g. chloroform,acetone,ether,etc.  All amino acids which make up proteins are L-α- aminoacids.
  98. 98. Semi-essential aminoacids. These include Arginine and Histidine.These are growth promoting factors since they are not synthesized in sufficient quantity during growth. SELENOCYSTEINE- the 21st amino acid.
  99. 99. The Genetic Code A codon consists of three consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide (protein).
  100. 100. The Codon Table  Sixty-four combinations are possible when a sequence of three bases are used; thus, 64 different mRNA codons are in the genetic code.
  101. 101.  Some codons do not code for amino acids; they provide instructions for making the protein.  More than one codon can code for the same amino acid.
  102. 102. All organisms use the same genetic code (A,T,C,G). This provides evidence that all life on Earth evolved from a common origin.
  103. 103. Cracking the Code  This picture shows the amino acid to which each of the 64 possible codons corresponds.  To decode a codon, start at the middle of the circle and move outward.  Ex: CGA  Arginine  Ex: GAU  Aspartic Acid
  104. 104. Translation Translation takes place on ribosomes, in the cytoplasm.  The cell uses information from messenger RNA (mRNA) to produce proteins, by decoding the mRNA message into a polypeptide chain (protein).
  105. 105. Stapes of protein synthesis  1) requirements of the components- amino acids, ribosome, mRNA,tRNA, ATP  2)activation of amino acids  3)protein synthesis proper  4) chaperones and protein folding  5) post – translational modifications.
  106. 106. Source: http://www.coolschool.ca/lor/BI12/unit6/U06L01.htm
  107. 107. Key = Uracil = Adenine = Guanine = Cytosine Cytoplasm
  108. 108. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon
  109. 109. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon
  110. 110. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon
  111. 111. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA
  112. 112. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA
  113. 113. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA
  114. 114. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Amino AcidtRNA
  115. 115. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Amino AcidtRNA
  116. 116. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Amino AcidtRNA
  117. 117. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Amino AcidtRNA
  118. 118. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Amino AcidtRNA
  119. 119. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  120. 120. Key = Uracil = Adenine = Guanine = Cytosine Start Codon Codon Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  121. 121. Key = Uracil = Adenine = Guanine = Cytosine tart Codon Codon Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  122. 122. Key = Uracil = Adenine = Guanine = Cytosine odon Codon Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  123. 123. Key = Uracil = Adenine = Guanine = Cytosine n Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  124. 124. Key = Uracil = Adenine = Guanine = Cytosine Codon Codon Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  125. 125. Key = Uracil = Adenine = Guanine = Cytosine Codon Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  126. 126. Key = Uracil = Adenine = Guanine = Cytosine on Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  127. 127. Key = Uracil = Adenine = Guanine = Cytosine on Stop Codon Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond
  128. 128. Key = Uracil = Adenine = Guanine = Cytosine Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond Amino Acid Chain
  129. 129. Key = Uracil = Adenine = Guanine = Cytosine Ribosome Anticodo Amino AcidtRNA Polypeptide Chain Peptide Bond Final Protein in Tertiary Structure
  130. 130. translation  Initiation codon AUG  Termination codons or non-sense codons or stop signals UAA UAG UGA
  131. 131. Messenger RNA (mRNA) 1) The mRNA that was transcribed from DNA during transcription, leaves the cell’s nucleus and enters the cytoplasm.
  132. 132. Transfer RNA(tRNA) 2) The mRNA enters the cytoplasm and attaches to a ribosome at the AUG, which is the start codon. This begins translation. 3) The transfer RNA (tRNA) bonds with the correct amino acid and becomes “charged.” (in the cytoplasm) 4) The tRNA carries the amino acid to the ribosome.  Each tRNA has an anticodon whose bases are complementary to a codon on the mRNA strand. (The tRNA brings the correct amino acid to the ribosome.) Ex: The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine.  The ribosome also binds the next codon and its anticodon.
  133. 133. The Polypeptide “Assembly Line” 5) The ribosome moves along the mRNA and adds more amino acids to the growing polypeptide or protein  The tRNA floats away, allowing the ribosome to bind to another tRNA.  The ribosome moves along the mRNA, attaching new tRNA molecules and amino acids.
  134. 134. Completing the Polypeptide 6) The process continues until the ribosome reaches one of the three stop codons on the mRNA, and then the ribosome falls off the mRNA. 7) The result is a polypeptide chain or protein that is ready for use in the cell.
  135. 135. mRNA binds to the ribosome and the code is read.
  136. 136. mRNA binds to the ribosome and the code is read.
  137. 137. tRNA has the anticodon and amino acid attaches. Guanine Cytosine Adenine Uracil
  138. 138. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil
  139. 139. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil
  140. 140. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil Thr
  141. 141. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil ThrGlu
  142. 142. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil ThrGluThr
  143. 143. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil ThrGluThrAsp
  144. 144. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil ThrGluThrAspCys
  145. 145. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil ThrGluThrAspCysLeu
  146. 146. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil ThrGluThrAspCysLeuThr
  147. 147. Amino acids bind to each other through peptide bonds. Guanine Cytosine Adenine Uracil ThrGluThrAspCysLeuThrSTOP
  148. 148. Ribosome hits the stop codon, and protein synthesis is complete. Guanine Cytosine Adenine Uracil ThrGluThrAspCysLeuThrAsp Stop Codon
  149. 149. Ribosome hits the stop codon, and protein synthesis is complete. Guanine Cytosine Adenine Uracil ThrGluThrAspCysLeuThrAsp Stop Codon
  150. 150. Ribosome hits the stop codon, and protein synthesis is complete. Guanine Cytosine Adenine Uracil ThrGluThrAspCysLeuThrAsp Stop Codon
  151. 151. Amino acid chain coils into a complete protein.
  152. 152. Amino acid chain coils into a complete protein.
  153. 153. Source: http://www.biochem.arizona.edu/classes/bioc471/pages/Lecture1/Lecture1.html

×