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40 Cards in this Set

  • Front
  • Back
What does transcription of DNA create?
What enzyme is responsible for transcribing DNA in bactera?
RNA polymerase
What direction does RNA polymerase work in?
5' --> 3'
Does RNA polymerase require a primer?
What does RNA polymerase match to a base in a gene?
a ribonucleotide triphosphate
What kind of a bond forms between the 3' end of a growing mRNA chain and a new ribonuclotide?
a phosphodiester bond
What is a phosphodiester bond?
A C--OH + P
becomes C--P
What is a ribonuclotide triphosphate?
a five carbon sugar ribose and a nitrogen base with 3 phosphates instead of one
What is the strand that is read be RNA polymerase called?
The template strand
What is the name of the strand not read by RNA polymerase?
The non-template strand
What is the difference in bases in RNA as opposed to DNA
RNA has uracyl instead of thymine
What is the role of DNA?
To store information
What is the role of RNA?
To carry information
What is the product of transcription and translation?
A protein
How do the majority of antibiotics work?
They interupt trancription or translation
What is a promoter?
A short sequence of DNA that facillitates binding of RNA polymerase to enable transcription of downstream genes. The start site for transcription. It contains the consencus sequence such as -10 box or -35 box
What is a sigma factor?
A detachable subunit of RNA polymerase that is responsible for guiding RNA polymerase to the TATA box, to start transcription.
what is a Holoenzyme
an enzyme that consists of a core enzyme (which contains the active site) and other proteins.
What binds to the promoter on DNA?
The sigma/RNA polymerase complex
What is the initiation complex?
RNA polymerase + sigma + promotor
What is the first step of the initiation phase?
Sigma protein binds to the promoter region of DNA
What is the second step of initiation?
The Sigma protein opens the DNA double helix; transcription begins
What is the third step of initiation?
Sigma releases; mRNA synthesis continues.
Which DNA strand is used as a template to synthesize RNA?
Either strand can be used depending on the location of the promoter.
How does RNA polymerase know when to stop transcribing a gene?
in most cases when RNA polymerase reaches a strech of DNA that functions as a transcription termination signal. As soon as this mRNA is synthysized it folds back on itself formin a hairpin. This distrupts RNA poly. and causes it to detach.

in rare cases an interaction occurs between RNA
polymerase and specific “termination proteins”
How does Eukaryotic RNA poly differ from Prokaryotic RNA poly?
Eukaryotes have three different RNA poly's: RNA poly I for large Ribosomal RNA, poly II for proteins, and RNA III for tRNA's and small ribosomal RNA
What are basal transcription factors?
These are proteins that initiate eukaryotic transcription by matching the enzyme with the appropriate promotor region in DNA.

Eukaryotes have many basal transcription factors.
What are promoter-proximal elements?
In eukaryotes, regulatory sequences that are close to a promoter and that can bind regulatory transcription factors.
What is the TATA box?
a unique sequence in Eukaryotic DNA, located 30 base pairs upstream of the transcription start site, to which RNA poly II can bind
What are specific
regulatory factors such as enhancers that effect the transcription of genes.
What experiment proved the existance of transcription factors.
An in-vitro system was used in which a region of
DNA containing one
promoter was used. Then one half of the experiment recieved RNA
polymerase and the
monomers (NTPs)
necessary to make
RNA transcripts.
In the other half of the
experiment, these
two ingredients plus
transcription factors were added.

Only the experiment with the transcription factors produced a singular strand of RNA. The other produced various chunks of RNA. (gel electrophorisis was used)
Is a gene in eukaryotes coded by a continuous section of DNA?
no, there exist introns which are NOT expressed in the final RNA transcript and must be removed.
What are exons?
Portions of DNA that are expressed.
How was the existance on introns and exons discovered?
When DNA was made to bond with its mRNA transcript it was found that the DNA was much longer and looped around in certain places.
How are introns edited out of the final message?
Several proteins called snRNPs assemble around an intron to form a spiceosome. A loop is formed by the intron (key is an adenine nucleotide). The 3' end of and exon is attached to the 5' of another, the sequence bonds, the spicosome releases with the intron.
What is the primary RNA transcript?
The RNA transcript that still includes introns.
What is the purpose of a 5' cap and a poly (A) tail?
To protect the message. They prevent the mRNA from degrading

The 5' cap also serves as a recognition signal for translation machinary.
What adds the Poly A tail?
the enzyme
poly(A) polymerase
What does it mean to be Polycistronic?
one mRNA codes for more than one polypeptide

Prokaryotes are polycistronic.
What does it mean to be moncistronic?
one mRNA codes for only one polypeptide.

Eukaryotes are usually moncistronic.