Transcription Flashcards
(41 cards)
RNA synthesis is catalyzed by ……. . RNA is synthesized in ……. direction.
RNA polymerase
5’ - 3’ direction
The function of tRNA is ……
transfer the amino acid sequence of proteins
* Contains anticodon (complementary to mRNA codons, composed of 3 base pairs)
Only one of the two DNA strands is transcribed into RNA. T/F
True
Define the promoter region for transcription
The region on the DNA that binds RNA polymerase and initiates the transcription
What is Pribnow box?
an A-T rich region (TATATT) located 10 base pairs away from the site where transcription begins (on the 5’ side)
What is hexamer 35 sequence?
a sequence of six nucleotides (TTGACA) located 35 base pairs away from where the transcription begins (on the 5’ side)
What is the benefit of Pribnow box and the hexamer 35?
initial recognition of the promoter region by the RNA polymerase
* These two comprise the consensus region
The first nucleotide transcribed in RNA is normally …..
purine (A or G)
Termination of the transcription involves both …… & ……
release of the DNA template & the synthesized RNA from the RNA polymerase
What are the ways for termination of transcription?
- Rho independent: the new RNA folds back on itself and forms a hair pin loop. The loop must be followed by 6-8 U residues forming a weak bond with 6-8 A residues in the DNA. These two features signal the end of transcription
- Rho dependent: this factor displaces the polymerase from the termination site. It requires ATP and RNA greater than 50 bases long
RNA polymerase is composed of two regions, ….. & ……
the core region & the holoenzyme region
- The core region is capable of polymerization, but can not recognize the promoter region. It has four subunits (alpha2, beta, beta’)
- The holoenzyme region recognized the promoter region (has a sigma subunit)
What are the requirements for RNA synthesis?
All four ribonucleotides (ATP, UTP, CTP, GTP), Mg & a DNA template.
RNA synthesis requires a primer. T/F?
False. It doesn’t require a primer, and does not proofread or repair errors
RNA synthesis proceeds in …… direction, and each time a nucleotide is added, ….. is released
5’-3’
pyrophosphate
What is the function of each of the prokaryotic RNA polymerase subunits?
Alpha: binds to the consensus sequences in the prokaryotic DNA promoter region
Beta: binds nucleotide triphosphate and forms the phosphodiester bond of the chain
Beta’: binds the polymerase to the DNA template
Sigma: recognition of the promoter region and provides the enzyme with specificity.
RNA transcription involves 3 steps , …., …. & …..
initiation, elongation & termination
see p. 385
RNA polymerase moves along the DNA template strand in ….. direction
3’ to 5’
Rifampin inhibits ….. of RNA synthesis, while Actinomycin ……
initiation
binds to DNA and prevent the polymerase movement along the template
In eukaryots, each type of RNA is transcribed by ……
a different RNA polymerase
* The requirements are the same for prokaryotic RNA, and can’t proofread or repair
The most abundant RNA in the cell is ….. . Transcribed by ….. which is localized in ……. . The subtypes transcribed are …, …. & ….
rRNA
RNA polymerase I
nucleolus
28S, 18S, 5.8S
mRNA is transcribed by ……. , which is found in the ……
RNA polymerase II
nucleoplasm
* mRNA is the least prevalent type of RNA. Contains complement to DNA template and to tRNA anticodon
RNA polymerase III transcribes …..
tRNA and 5S rRNA
RNA polymerase enzymes can work by themselves. T/F?
True
No primer is required, but they can’t proofread or correct errors
Enhancer sequences bind factors that ……, while silencer sequences bind factors that ….
increase the rate of transcription
decrease the rate of transcription
