Pages in this set

Page 1

Preview of page 1
Lecture 6: The 'central dogma' of molecular biology

Information stored as the base pair sequence of DNA encodes the amino acid sequences of the
thousands of proteins present in any given cell. The coded information in a gene sequence is first
TRANSCRIBED into an RNA nucleotide sequence and then TRANSLATED…

Page 2

Preview of page 2
'RNA' as if it were a homogeneous substance but there are different functional types of RNA.
Some are enzymes (!) others have unknown functions.

Messenger RNA (mRNA).
This acts as genetic intermediate, carrying information from the gene (i.e. DNA) to the protein
synthesis machinery (i.e.ribosomes).
In eukaryotes, this means that…

Page 3

Preview of page 3
In this context, what is meant by the term COGNATE?
a tRNA and its corresponding amino acid

Transcription (RNA synthesis) in E. coli
RNA polymerase is a highly processive enzyme that catalysis the reaction:
(RNA)n + NTP (RNA)n+1 + PPi

RNA polymerase requires NTPs plus Mg 2+ and a double-stranded…

Page 4

Preview of page 4
In bacteria, a single type of RNA polymerase makes all of the different kinds of RNA. In
eukaryotes, there are multiple RNA polymerases each making a different type of RNA.

Both strands of DNA are used as templates for transcription but not over their whole length, so that,
at any…

Page 5

Preview of page 5
If the heat-denatured DNA is then cooled rapidly, the strands will stay apart because they will
not have time to line up correctly and ANNEAL together again.
Annealing (a process also referred to as RENATURATION or HYBRIDISATION) will occur, however,
if the DNA is cooled slowly.
This can be utilised…

Page 6

Preview of page 6
Following the action of E. coli RNA polymerase on phage DNA, the resultant
TRANSCRIPT (i.e. the RNA product) was found to hybridise with only one
Strand of the DNA.
Thus, RNA polymerase makes a complimentary copy
Of only one DNA strand during transcription.

In summary, each RNA molecule (messenger, ribosomal…

Page 7

Preview of page 7
subunit helps find sites on the DNA where transcription begins ( promoter site)
at these sites participate in the initiation of RNA synthesis and then dissociates to from
the rest of the enzyme
random starts on foreign DNA

Both forms can transcribe 'foreign' DNA, but they do so with random…

Page 8

Preview of page 8
Post-transcriptional modification

meaning of: PRIMARY TRANSCRIPT; RNA PROCESSING; MATURE RNA. Here, we consider processing of
tRNA andrRNA. Processing of eukaryotic mRNA will be discussed in the next lecture.
Bacterial mRNA is not processed at all.

The primary transcript ('precursor tRNA') from…

Page 9

Preview of page 9
Mature tRNAs and the long rRNAs from both prokaryotes and eukaryotes are chemically
modified post-transcriptionally.
This occurs mainly on the primary transcripts although some modifications take place after
The principal forms of chemical modification are: pseudouridine formation (Greek letter psi,
) via isomerisation of specific (not all) uridine

Page 10

Preview of page 10
Rifamycin (semi-synthetic derivative = rifampicin) and Actinomycin D are specific inhibitors of
prokaryotic transcription although they act in fundamentally different ways.

How do the modes of action of these drugs differ?
Rifampicin is a compound derived from a strain of Streptomyces
Specifically inhibits the initiation of RNA synthesis
Interferes with…


No comments have yet been made

Similar Dance resources:

See all Dance resources »