DNA transcription & RNA modification Flashcards
is the first step in gene expression
transcription
at the molecular level, a _______ is a segment of DNA used to make a functional product (either an RNA or a polypeptide)
gene
means the act or process of making a copy
transcription
copying DNA sequences with RNA
transcription
the structure of DNA is not altered as a result of ______________ process
(it can continue to store info)
transcription
the overall process by which the info within a gene is used to produce a functional product which can, in concert with environmental factors, determine a trait.
gene expression
structural genes encode the _________ _______ sequence of a polypeptide
amino acid
steps of gene expression
- transcription produces messenger RNA (mRNA)
- the mRNA is translated into amino acid sequences
- the synthesis of functional proteins determines an organisms traits.
produces a RNA copy of a gene
transcription
a temp. copy of a gene
mRNA
production of amino acid chain (polypeptide)
translation
becomes part of a functional protein that contributes to an organisms traits
polypeptide
- the DNA strand that is actually transcribed
- the RNA transcript is reverse compliment
template strand
________ _______ aka sense strand aka nontemplate strand
coding strand
the base sequences is ________ to the RNA transcript (except for the substitution of uracil in for thymine)
identical
RNA transcripts play different functional roles:
> 90% of all genes are structural genes which are transcribed into mRNA
-only mRNA is translated into amino acid seqs
the RNA transcripts from nonstructural genes are not ______________
- important cellular functions
- they can still ________ traits
- RNA transcript can become part of a complex that contains _______ subunits (ex: ribosomes, spliceosomes, signal recognition particles, telomerase)
translated
confer
protein
DNA seq define the beginning of a gene
promotors
DNA seq define the end of a gene
-signal the end of transcription
terminators
regulation of the level of RNA synthesis
regulatory sites
proteins must recognize and interact with DNA to produce mRNA
transcription factors
the stages of transcription:
- initation: transcription factors interact with promoter seq and enables RNA polymerase to bind to promotor (DNA is denatured)
- elongation: RNA polymerase synthesizes RNA
- Termination
Termination: ___________ seq reached.
-RNA polymerase and RNA ___________ from DNA
terminatior
dissociate
transcription in baceria:
regulation
initiation and promotion
elongation
termination
promoter region (pribnow box 1975) -seq elements (-35 seq., -10 seq)
initiation and promotion in bac
promotor regions are ___________ not __________
similar not identical
most commonly occurring bases
consensus seq
RNA polymerase, an _________, binds to DNA
-components (core enzymes, composed of ___ subunits
alpha, beta, omega, sigma factor, the 6th subunit (what does each one do?)
enzyme 5 alpha: assembly of holoenzyme, DNA binding beta: DNA binding, RNA synthesis omega: assembly of core enzyme
Core enzyme + sigma factor
RNA polymerase holoenzyme
initiation and promotion: RNA polymerase binds at ___________
-RNA polymerase slides along DNA (_________ factor binds to the promotor)
regulatory
sigma
binding of a ________ factor protein in RNA pol to DNA double helix
sigma
RNA polymerase _____________ dna at -10 region (TATAAT)
-OPEN complex
denatures
sigma factor jettisoned as _______ transcription starts
RNA
initiation and promotion:
- form ____________/bind to DNA
- sigma factor binds to _________
- initiate open complex
- transcribe RNA
- eject sigma factor
holoenzyme
promoter
RNA elogation/ synthesis:
- ____ nucleotides/second rNTPs connect to 5’ to 3’(3’ OH to 5’ PO4)
- AU/GC rule (AUGC, UACG)
- RNA pol _________ to RNA (RNA attached to ________ DNA)
43
attached
template
transcription termination:
- ____________ RNA-DNA releases RNA plymerase
- Rho-dependent termination (sometimes, Rho-protein is ___________)
- Rho-independent termination (sometimes, _____ proteins are required)
denaturing
required
NO
Rho utilization site (rut) (upstream of the termination site)
- Rho binds to rut (like a helicase-unzips)
- Rho follows RNA polymerase
rho-dependent termination
Terminator encodes a _________(binds to RNA polymerase)
-RNA polymerase pauses (Rho unzips RNA-DNA)
hairpin
Rho-dependent termination
- also called intrinsic termination
- terminator( hairpin seq followed by uracil rich seq)
- hairpin binds RNA pol (momentum pulls apart RNA-DNA)
Rho-INDEPENDENT TERMINATION
more complex than in prokaryotes
-organelles and multicellularity requires more ________
_______________ __________-different genes expressed in different cells
-requires timing and coordination
transcription in eukaryotes
genes
developmental genetics
transcribes ribosomal RNA rRNA (except 5S rRNA)
polymerase I
transcribes all structural genes (all mRNA and some snRNA)
polymerase II
transcribes all transfer RNA + 5S rRNA
polymerase III
all polymerases are __________
similar
eukaryotic promotor sequences are more _________ and often more complex than those of baceria
variable
for structural genes, at least three features are found in most promotors:
- regulatory elements
- TATA box
- transcriptional start site
_________ ____ (-25) instead of pribnox box (-10): determines transcription start site
TATA box
upstream of core promoter
enhancers and silencers
regulatory DNA elements
on same chromosome as regulated genes
-TATA box, enhancers, silencers
Cis-acting elements (regulation)
genes that encode transcription factors that control expression of other genes
trans-acting elements (regulation)
_________ ______ transcription initiation:
3 categories of proteins required for initiation
structural gene
- rna polymerase II
- general transcription factors (GTF)
- mediator
_________ are always DNA seq
elements
_________ are always proteins that interact with elements
factors
Prok colinearity (1:1 DNA codons match amino acids)
- eukaryotes don’t always exhibit colinearity
- post transcription, RNA is modified
RNA modification
_________ are transcribed and translated
-introns are transcribed, but not ___________
exon, translated
exonucleases cleave nucleotides from the end of a strand
RNA cleavage
endonucleases cleavage nucleotides in the middle of the strand
RNA cleavage
types of RNA modification ::
processing splicing 5' capping 3' polyA tailing RNA editing base modification
Degrading cleaving the ends of an RNA molecule
-RNaseP is a ribosyme(RNA portion is a caralyst)
processing transfer RNA (tRNA)
________-_________ in group I and II introns.
-proteins called maturates enhance splicing rate
self-splicing (uncommon)
- splicing pre-mRNA
- large complex composed of snRNPs(small nuclear RNA&proteins)
- recognize intron-exon boundaries
- dictate configuration of pre-mRNA
- catalyze removal of introns
spliceosome splicing (common)
intron recognition seq:
- characteristic RNA seq define the boundaries of an intron
- 5’ splice site
- branch site
- 3’ splice site
mature mRNA’s have a 7-methylguanosine attached to 5’ end
-polyA tail on 3’ end
capping and tailing pre-mRNAs
changing nucleotide seq of RNA molecule:
-insertions or deletions
-conversion of one base to another
effects:
-generate start or stop codons
-changing codons (downstream, amino acids)RNA editing
