BIO211 -
CELLULAR AND ORGANISMAL BIOLOGY
Lecture Outline
for
Topics: Transcription
Chapter 13 sections 13.1, 13.2
Figures used in lecture: 13.1, 13.2, 13.6, 13.7, 13.9,
Additional Resources
Central
Dogma – includes descriptions of the 3 types of RNA
One-gene-one-polypeptide
– Beadle and Tatum and Neurospora
Transcription
– in more detail
Transcription:
making an RNA copy of a DNA sequence
One Gene One Enzyme (Polypeptide) Hypothesis
The function of a
gene is to control the production of a single, specific polypeptide.
This hypothesis is supported by the work of Beadle and Tatum
on nutritional mutants of Neurospora
crassa.
Define/explain:
prototroph, auxotroph, mutant
You should understand and be able to explain the work of
Beadle and Tatum (pages 221-222, Figure 11.5)
DNA, RNA, Flow of Information
|
Nucleic Acid |
Function |
Sugar |
Bases |
No. of strands |
Stability |
|
DNA |
Info storage |
deoxyribose |
A, T, C, G |
Double stranded |
More stable |
|
RNA |
Info transfer |
ribose |
A, U, C, G |
Single stranded |
Less stable |
Central Dogma: DNA codes for the production of RNA
(transcription), RNA codes for the production of protein (translation), and
proteins do not codes for the production of DNA, RNA, or protein
DNA gene genotype
transcription
RNA
translation
protein enzyme phenotype
Transcription
Define: messenger RNA (mRNA), template strand, RNA
polymerase, promoter, termination signal
You should be able
to
1. Explain the purpose of transcription within
the framework of the Central Dogma.
2. Describe the steps of transcription including
the functions of RNA polymerase.
3. Explain how the RNA polymerase
"knows" what parts of the chromosome to transcribe.
Three kinds of RNA:
Messenger RNA (mRNA) –
Ribosomal RNA (rRNA) –
Transfer RNA (tRNA) –
Transcription -
-
base-pair complimentarity:
DNA base RNA
base
C G
G C
T A
A U
RNA polymerase -
- enzyme that synthesizes RNA from a DNA template
- new RNA is synthesized in the 5’ to 3’ direction
- new RNA nucleotides are added to the free 3’-OH on the
last sugar