Tufts Bio 13 Chapter 16 Transcription

Front 1

What does transcription of DNA create?

Back 1

mRNA

Front 2

What enzyme is responsible for transcribing DNA in bactera?

Back 2

RNA polymerase

Front 3

What direction does RNA polymerase work in?

Back 3

5' --> 3'

Front 4

Does RNA polymerase require a primer?

Back 4

No

Front 5

What does RNA polymerase match to a base in a gene?

Back 5

a ribonucleotide triphosphate

Front 6

What kind of a bond forms between the 3' end of a growing mRNA chain and a new ribonuclotide?

Back 6

a phosphodiester bond

Front 7

What is a phosphodiester bond?

Back 7

A C--OH + P
becomes C--P

Front 8

What is a ribonuclotide triphosphate?

Back 8

a five carbon sugar ribose and a nitrogen base with 3 phosphates instead of one

Front 9

What is the strand that is read be RNA polymerase called?

Back 9

The template strand

Front 10

What is the name of the strand not read by RNA polymerase?

Back 10

The non-template strand

Front 11

What is the difference in bases in RNA as opposed to DNA

Back 11

RNA has uracyl instead of thymine

Front 12

What is the role of DNA?

Back 12

To store information

Front 13

What is the role of RNA?

Back 13

To carry information

Front 14

What is the product of transcription and translation?

Back 14

A protein

Front 15

How do the majority of antibiotics work?

Back 15

They interupt trancription or translation

Front 16

What is a promoter?

Back 16

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

Front 17

What is a sigma factor?

Back 17

A detachable subunit of RNA polymerase that is responsible for guiding RNA polymerase to the TATA box, to start transcription.

Front 18

what is a Holoenzyme

Back 18

an enzyme that consists of a core enzyme (which contains the active site) and other proteins.

Front 19

What binds to the promoter on DNA?

Back 19

The sigma/RNA polymerase complex

Front 20

What is the initiation complex?

Back 20

RNA polymerase + sigma + promotor

Front 21

What is the first step of the initiation phase?

Back 21

Sigma protein binds to the promoter region of DNA

Front 22

What is the second step of initiation?

Back 22

The Sigma protein opens the DNA double helix; transcription begins

Front 23

What is the third step of initiation?

Back 23

Sigma releases; mRNA synthesis continues.

Front 24

Which DNA strand is used as a template to synthesize RNA?

Back 24

Either strand can be used depending on the location of the promoter.

Front 25

How does RNA polymerase know when to stop transcribing a gene?

Back 25

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”

Front 26

How does Eukaryotic RNA poly differ from Prokaryotic RNA poly?

Back 26

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

Front 27

What are basal transcription factors?

Back 27

These are proteins that initiate eukaryotic transcription by matching the enzyme with the appropriate promotor region in DNA.

Eukaryotes have many basal transcription factors.

Front 28

What are promoter-proximal elements?

Back 28

In eukaryotes, regulatory sequences that are close to a promoter and that can bind regulatory transcription factors.

Front 29

What is the TATA box?

Back 29

a unique sequence in Eukaryotic DNA, located 30 base pairs upstream of the transcription start site, to which RNA poly II can bind

Front 30

What are specific
transcription
factors?

Back 30

regulatory factors such as enhancers that effect the transcription of genes.

Front 31

What experiment proved the existance of transcription factors.

Back 31

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)

Front 32

Is a gene in eukaryotes coded by a continuous section of DNA?

Back 32

no, there exist introns which are NOT expressed in the final RNA transcript and must be removed.

Front 33

What are exons?

Back 33

Portions of DNA that are expressed.

Front 34

How was the existance on introns and exons discovered?

Back 34

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.

Front 35

How are introns edited out of the final message?

Back 35

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.

Front 36

What is the primary RNA transcript?

Back 36

The RNA transcript that still includes introns.

Front 37

What is the purpose of a 5' cap and a poly (A) tail?

Back 37

To protect the message. They prevent the mRNA from degrading

The 5' cap also serves as a recognition signal for translation machinary.

Front 38

What adds the Poly A tail?

Back 38

the enzyme
poly(A) polymerase

Front 39

What does it mean to be Polycistronic?

Back 39

one mRNA codes for more than one polypeptide

Prokaryotes are polycistronic.

Front 40

What does it mean to be moncistronic?

Back 40

one mRNA codes for only one polypeptide.

Eukaryotes are usually moncistronic.