RNA synthesis: Transcription of

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RNA synthesis Transcription of The Genetic Code.

• General considerations.
• The RNA polymerase
• Initiation the promoter and sigma factor
• Elongation
• Chain termination
• Eukaryotic RNA processing.

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DNA synthesis on the lagging strand.
C F
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Transcription Synthesis of RNA from a DNA
template.
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• RNA is initially synthesized using
• a DNA template in the process
• called transcription.
• The enzyme is DNA-dependent
• RNA polymerase.

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Coding strand
Template Strand.
RNA polymerase
C F
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• Two strands of DNA
• Template strand (-strand)
• 2) Coding strand (strand)

RNA polymerase reads this 3 to 5
The RNA synthesized will have the same sequence
as this except the T will be replaced by U.
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RNA is synthesized 5 to 3
The template strand of DNA is read 3 to 5.
By convention, control sequences are read 5 to
3 on the coding strand. 5 end upstream 3
enddownstream.
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Upstream (-) Downstream ()
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• The polymerase

DNA-dependent RNA polymerase 4 kinds of
subunits a2, b, b, w and s.
b b make up the active site.
a2, b, b, and w makes up the core enzyme.
s is loosely bound tells the enzyme where to
start which strand to read.
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Transcription can be divided into 3
parts. A. Chain initiation B. Chain
elongation C. Chain termination.
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3. Chain initiation the sigma factor.
How does RNA polymerase know where to
start? Site on the DNA promoter Sigma factor
part of the polymerase
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The s binds to a promoter region on the DNA
tells it where to start which strand to
read. It drops off after about 10
nucleotides have been added. More than 1 type of
s factor.
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• Chain
• elongation

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• Chain termination
• 1) Inverted repeats
• 2) Rho factor

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• Inverted
• repeats

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2) The rho factor.
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2. Transcription in eukaryotes. A.Separation of
transcription and translation. B. mRNA
structure Introns and exons.
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• Separation of transcription and
• translaterion.
• Transcription occurs in the nucleus
• Translation occurs in the cytoplasm.

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mRNA in eukaryotes intron exons.
exon
intron
3 polyA tail.
5cap
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Splicing removes the introns. There may be
alternate ways of splicing.
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B. mRNA in eukaryotes intron exons.
exon
intron
3 polyA tail.
5cap
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Alternative splicing.
Fast skeletal muscle troponin T.