Gene Expression Flashcards
(57 cards)
- is the process wherein genetic information from DNA is transferred into RNA.
- It is the first step in the expression of the
genetic information stored in the genome:
from gene to gene product (frequently a
protein).
Transcription
It became very rapidly clear in the 50s that
DNA could not be directly converted into
protein, and there had to be an intermediate
step.
● This unstable product was identified as
RNA
● It is a single-stranded molecule that
contains Uracil instead of Thymine.
● It uses ribose sugar instead of
deoxyribose
RNA
Three major classes of RNA:
They participate in protein synthesis and are synthesized from DNA by transcription
- Ribosomal RNA, rRNA
- Transfer RNA, tRNA
- Messenger RNA, mRNA
Other forms of RNA:
- small nuclear RNA (snRNA).
- small nucleolar RNA (snoRNA).
- microRNA (miRNA). ~22 nt RNA molecules that regulate the expression of mRNA molecules.
- long non-coding RNA (lncRNA).
- siRNA – RNA interference»_space;> 2006 Nobel Prize Andrew Z. Fire & Craig C. Mello
(snRNA).
small nuclear RNA
(snoRNA).
small nucleolar RNA
(miRNA). ~22 nt RNA molecules that regulate the expression of mRNA molecules.
microRNA
(lncRNA).
long non-coding RNA
siRNA –»_space;> 2006 Nobel Prize Andrew Z. Fire & Craig C. Mello
RNA interference
is a segment (or segments) of the DNA with a distinct
sequence of nucleotides that is transcribed and translated into a
protein product that contributes to the expression of a specific
phenotype/function
gene
The sequences after the transcription initiation site towards the 3’ end of the template strand are called
upstream elements
while those sequences before the transcription termination site towards the 5’ end are
called the
downstream elements
The CORE enzyme has five subunits (~400 kDa)
β’, β, α, αCTD, ω
: largest subunit, encoded by rpoC.
Contains part of the active center responsible for RNA synthesis
β’
: second-largest subunit, encoded by rpoB.
Contains the rest of the active center responsible for RNA synthesis.
β
: third-largest subunit and is present in two copies per molecule of
RNA pol, αI and αII. Each α contains two domains: αNTD (N-Terminal
domain) and αCTD (C-terminal domain). αNTD required for assembly
of RNA pol
α
required for interaction with the promoter, non-sequence/non
specific interactions at most promoters and sequence-specific
interactions at upstream-element-containing promoters. α interacts
with regulatory factors.
αCTD
: smallest subunit. ω facilitates assembly of RNAP and stabilizes
RNAP
ω
TREU OR FALSE
RNA polymerases in some living organisms
are evolutionary relate
False: all
EVENTS IN TRSNCRIPTION:
the RNA polymerase, together with any
initiation factors required, binds to the promoter, the DNA
sequence where transcription starts.
● Once formed, the promoter-polymerase complex
undergoes structural changes required for initiation to
proceed.
● The DNA will then unwind around the point where
transcription will start.
● The base pairs are disrupted, producing a “transcription
bubble” of single-stranded DNA.
● The new ribonucleotide is added to the 3’ end of the
growing strand since transcription always occurs in a 5’
to-3’ direction.
Initiation
TRUE OR FALSE
Only one RNA strand acts as a template on which the RNA strand is built.
False: DNA
This strand is called the template strand or
?
antisense strand or non-coding strand.
The other strand to where the code being copied is located is called the non-template strand or?
the sense strand or the coding strand.
