finals - transcription Flashcards
(T/F) the 3’OH at end of growing DNA chain is a nucleophile and attacks phosphorus next to sugar in nucleotide
true
(T/F) RNA transcription and subsequent translation into protein is done by the cell at any particular time
false
is tighty tied to the cell’s needs. only produced when needed
____ the process by which a region of DNA is copied to RNA
transcription
which of the ff does not apply to RNA?
a. consists of four nucleotide subunits joined by phosphodiester bonds
b. contains pentose sugar ribose instead of deoxyribose
c. Uracil basepairs with thymine through hydrogen bonding
d. RNA is typically single stranded
C
U = A
replaces thymine
(T/F) Uracil differs from thymine by the absence of a CH3 on carbon 5
true
(T/F) RNA and DNA contains -OH group attached to the 2’ carbon of ribose
false
DNA = H on 2C RNA = -OH on 2C
(T/F) Occasionally uracil will also basepair with guanine
true
(T/F) Single stranded structure of RNA allows it to fold into a variety of shapes dictated by the RNA sequence which is different with the tertiary structure of proteins
false
first part true. folding is analogous to 3’ structure of proteins
(T/F) RNA shape due to folding is stabilized by both conventional basepairing between complementary
nucleotides and nonconventional basepair interactions
true
(T/F) RNA transcripts are complementary to both strands of DNA
false
only to one strand
____ the strand of DNA that is complementary to RNA
template or antisense strand
______ the strand of DNA that has the same sequence as the RNA except that T replaces U
sense / coding / non template strand
____ each of the transcribed segment of DNA
transcription unit
____ usually consist of a single gene and encode a
single RNA or single protein or may encode a group of related protiens
Eukaryotic transcription units
(T/F) bacterial transcription unit is polycistronic, therefore one RNA thus encodes several distinct proteins
true
_____ term for when an entire set of adjacent genes is transcribed as a unit
polycistronic
(T/F) Eukaryotic transcription units may encode a group of related proteins if the initial RNA transcript is spliced
in multiple ways that can produce different proteins
true
(T/F) In bacteria, a transcription unit often consists of different sets of genes
false
unit = set of adjacent genes typically found in operons
(T/F) majority of a cell’s genes transcribed into tRNA that encodes amino acids for protein translation
false
this is mRNA
____ the RNA type that form core of ribosomes and catalyze protein synthesis and is the most abundant type
Ribosomal RNA (rRNA)
____ the RNA type that serves as adaptors between amino acids and mRNA during protein synthesis
Transfer RNA (tRNA)
____ the RNA type that results from direct splicing of premRNA to mRNA
Small nuclear RNA (snRNA)
____ the RNA type that function in the processing and chemical modification of rRNA
Small nucleolar RNA (snoRNA)
_____ are ds RNAs about 19-25 nucleotides long that are related and regulate gene expression through the mechanism of RNA interference (RNAi)
MicroRNAs (miRNAs) and small interfering RNAs (siRNAs)
(T/F) miRNAs and siRNAs Inhibit gene expression at posttranscriptional level
true
____ the RNA type that typically exhibit imperfect complementarity with the 3’ end of a target mRNA and inhibit its translation
miRNAs
____ the RNA type that typically form perfect complementary duplexes with a target mRNA and lead to its degradation through specific enzyme pathways
siRNAs
(T/F) RNAs together with proteins, comprises most of the cell’s dry mass
false
RNA comprises a few percent of a cell’s dry weight and 3-5% of total RNA
_____ process by which siRNA inhibits gene expression in a targeted sequence specific
manner
RNA Interference (RNAi)
____ are derived from longer dsRNA precursors and first discovered in C. elegans but has since been found as a gene regulatory mechanism in other organisms including mammals
siRNAs
____ the endonuclease that cuts dsRNA into short pieces to form siRNA
dicer
(T/F) in the basic RNAi mechanism, the sense strand is loaded into the RISC and binds to target mRNA by basepairing
false
this is done with ANTISENSE strand
_____ RISC; degrades mRNA
RNA-induced silencing complex
(T/F) Experimental introduction of siRNA into cells induces expression of specific genes
false
it INHIBITS expression of sp genes
which of the ff is not part of regulation of gene expression done by RNAi?
a. Elimination of transcripts from mobile elements (transposons) and repetitive DNA
b. Dicer and RISC play central role in destruction of tRNAs
c. Block of protein synthesis by micro RNAs generated within the cell
d. Suppresses transcription and keeps chromatin condensed
B
destruction of invading viral RNA
which of the ff is not used to experimentally introduce siRNAs into cells to turn off specific gene products?
a. transfection
b. plasmid
c. viruses
d. direct injection
none of the above :)
______ when the X chromosome is transcriptionally inactivated during embryonic development and shows as this structure in the interphase cells
Barr body
____ the area in the X chromosome where random inactivation begins
Xinactivation center (XIC)
____ is encoded by XIC coats and inactivates one X chromosome apparently by helping to form transcriptionally inactive heterochromatin
XIST RNA
(T/F) the XIST RNA is translated into protein before it can perform its function
false
not translated
which of the ff does not apply to RNA polymerases?
a. Catalyze formation of phosphodiester bonds between nucleotides
b. unwinds DNA helix just ahead of its active site
c. polymerization is driven by hydrolysis of phosphate bonds
d. adds dNTPs to the growing RNA chain using exposed DNA template
D
adds ribonucleoside triphosphates (ATP, UTP, GTP, and CTP)
(T/F) RNA polymerase displaces RNA from DNA/RNA hybrid to allow DNA helix to rewind behind the polymerase
true
(T/F) RNA polymerase forms a transient short region of DNA/RNA hybrid
true
which of the ff does not apply to RNA synthesis?
a. RNA molecules are synthesized one at a time
b. RNA is released from the DNA strand as it is synthesized
c. Synthesis of new RNA molecules can start at one end of a gene as synthesis is completed at the other end
d. none of the above
A
many RNA molecules can be synthesized from the same gene simultaneously
(T/F) RNA pol like DNA pol, requires a primer to initiate RNA synthesis
false
does not require it
(T/F) RNA pol makes one mistake per 10^4 nucleotides copied versus one mistake per 10^7 nucleotides copied by DNA pol
true
(T/F) RNA pol, like DNA pol, catalyzes linkage of ribonucleotides
false
deoxyribonucleotides for
DNA pol
(T/F) Since RNA does not permanently store genetic information in cells like DNA, an error in RNA sequence has less potential to cause severe damage to cell
true
(T/F) RNA pol synthesizes RNA chain in the 3’ to 5’ direction
false
5’-3’ same direction as DNA pol synthesizes DNA
(T/F) RNA can also proofread its activity. it can back up, excise incorrect base and replace with correct one
true
____ a detachable subunit of the multisubunit complex bacterial RNA pol that is responsible for recognizing the site on the DNA where transcription should begin
sigma factor
____ The actual site of transcription initiation is indicated along a gene by a specific sequence of nucleotides
promoter
(T/F) The σ factor recognizes exposed portions of the bases in the promoter sequence and attaches the RNA pol tightly to the site to begin transcription
true
____ core polymerase plus σ factor
RNA pol holoenzyme
(T/F) step 1 in the transcriptional cycle in bacteria is the formation of RNA primers along the promoter
false
RNA pol holoenzyme forms and locates a promoter
(T/F) step 2 in the transcriptional cycle in bacteria is the unwinding of DNA by RNA pol at transcription initiation site
true