Chapter 7 and 8

Question 1

Extrons

Answer 1

encode proteins

Question 2

Introns

Answer 2

separate proteins

Question 3

Introns are spliced from preRNA via the

Answer 3

spliceosome

Question 4

Name a couple properties of RNA

Answer 4

1. RNA has ribose instead of deoxyribose
2. RNA is single stranded
3. RNA has A, G, C, and Uracil which is a pyrimidine
   U can pair with A and G only during folding but not during transcription
4. RNA can catalyze biological reactions

Question 5

Name two classes of RNA

Answer 5

mRNA is the intermediate between DNA and protein, while functional RNA functions by itself

Question 6

tRNA…

Answer 6

brings amino acids to mRNA in translation

Question 7

snRNA

Answer 7

unite with protein subunits to form the spliceosome that removes introns from mRNA

Question 8

RNA transcription goes in the

Answer 8

5’ to 3’ direction (pairs are added to the 3’ end)

Question 9

For any gene, how many strands of DNA are used?

Answer 9

Just one, no matter how many times the gene is replicated

Question 10

What happens in initiation stage for prokaryotes

Answer 10

RNA Polymerase binds to a promoter located close to the start of the 5’ to 3’ direction
RNA polymerase scans for DNA promoter sequence

Question 11

mRNA is usually the same as the

Answer 11

nontemplate strand except T is replaced with U

Question 12

What is the sigma factor?

Answer 12

a protein binding to the RNA polymerase, which “promotes” the expression of specific genes of the DNA, by binding or not to their promoter site(s). The sigma factor is usually released after transcription is complete

Question 13

TTG and TATAAT box: what are those?

Answer 13

promoter sequences that usually attract the RNA Polymerase II

Question 14

How does transcription terminate?

Answer 14

Transcription goes beyond protein segment of the gene, creating a 3’ untranslated region at the end of the transcript

Question 15

What are the two termination mechanisms?

Answer 15

Intrinsic and rho dependent: In intrinsic, the termination sequences are abundant in G and C which form a hairpin loop (3 H bonds between G and C as opposed to A and T’s 2 H bonds) which RNA stops after U to backtrack, but hairpin loop prompts whole sequence to snap off DNA template strand; rho factor is when RNA has a upstream segment called rut rich in C but poor in G; Rho binds to rut pauses polymerase, and breaks off RNA from RNA polymerase

Question 16

Three different type of polymerase molecules in eukaryotes. Name them

Answer 16

RNA polymerase I transcribes an RNA gene RNA Polymerase II transcribes all protein encoding genes from which mRNA is the result RNA Polymerase III transcribes small functional RNA genes (tRNA snRNA)

Question 17

Why is mRNA in eukaryotes cotranscriptional

Answer 17

5’ undergoes processing while 3’ is still being synthesized

Question 18

How does RNA polymerase III recognize promoter sequences

Answer 18

Requires general transcription factors to bind to regions in the promoter before binding of the core enzyme

Question 19

What’s the function of a general transcription factor

Answer 19

GTF’s find and bind to sequences in promoters or other GTFs and serve to attract the RNA polymerase II to position and start transcription

Question 20

Explain the TATA box

Answer 20

Usually the site of the first event, where the TBP or TATA binding protein attracts otehr GTFs and RNA Polymerase III to the promoter to start the preinitiation complex

Question 21

Explain the 3 stages of pre-mRNA processing

Answer 21

Adding a cap at the 5’ end, splicing to eliminate introns, and AAUAAA and a poly(A) tail is added to the mRNA

Question 22

CTD (Carboxy Terminal Domain)

Answer 22

Part of RNA Polymerase II near the site at which new pre mRNA emerges and helps bind with proteins to help with pre-mRNA processing

Question 23

Introns usually have

Answer 23

GU at the 5’ end and AG at the 3’ end

Question 24

How does intron removal work?

Answer 24

One end’s G attaches to an A in the middle of the intron, in which then the two exons are joined together, leaving the intron as free-floating.

Question 25

Spliceosomes operate with the help of

Answer 25

snRNAs (small nuclear RNAS)

Question 26

What molecule helps synthesize RNA primers

Answer 26

Primase

Question 27

DNA Polymerase I

Answer 27

Revomes the small primase fragments on the lagging strand

Question 28

Eukaryotes have how many genes per mRNA

Answer 28

Just one while prokaryotes have > 1 per mRNA