Quiz IV

Question 1

T or F: all genes are expressed into proteins.

Answer 1

F: only some genes are expressed into proteins

Question 2

What is RNA splicing?

Answer 2

Removal of non-coding intron sequences, leaving coding exons

Question 3

What is the final result of RNA splicing?

Answer 3

Messenger RNA (mRNA)

Question 4

What are the main processes that occur during gene expression? Explain what happens during each.

Answer 4

1. Transcription - DNA acts as a template for RNA synthesis
2. Splicing - removal of non-coding intron sequences, leaving coding exons in RNA transcript
3. Translation - Ribosome and tRNA translate codons in mRNA into sequence of amino acids

Question 5

What are the three types of RNA that play a role in protein synthesis?

Answer 5

1. Messenger RNA (mRNA)
2. Transfer RNA (tRNA)
3. Ribosomal RNA (rRNA)

Question 6

What are codons?

Answer 6

Groups of three nucleotides that specify the amino acid sequence

Question 7

When does translation occur?

Answer 7

After mRNA travels to cytoplasm

Question 8

Where is the mRNA positioned on the ribosome?

Answer 8

Small subunit

Question 9

What type of RNA helps mRNA position on the ribosome?

Answer 9

rRNA

Question 10

What are the two ends of tRNA?

Answer 10

1. Anticodon sequence
2. Amino acid

Question 11

What role does rRNA and the large ribosomal subunit play in translation?

Answer 11

Catalyzing formation of a peptide bond between two amino acids

Question 12

Catalyzing the formation of a peptide bond between two amino acids is done by which parts of the ribosome during translation?

Answer 12

1. rRNA
2. Large subunit

Question 13

What is transcription?

Answer 13

Process of synthesizing RNA from a DNA template

Question 14

The pre-initiation complex assembles around the _______ of a gene.

Answer 14

Core promoter

Question 15

What makes up the promoter in eukaryotes?

Answer 15

1. TATA box
2. Initiator sequence

Question 16

_________ bind at the TATA box.

Answer 16

General transcription factors

Question 17

General transcription factors bind at the _________.

Answer 17

TATA box

Question 18

Which part of the promoter contains the transcription start site?

Answer 18

Initiator sequence

Question 19

What is the direction of mRNA synthesis?

Answer 19

5’-3’ direction

Question 20

The newly-created mRNA strand represents a copy of the information in which DNA strand?

Answer 20

Coding strand

Question 21

What does RNA polymerase do?

Answer 21

Protein that transcribes DNA to RNA

Question 22

What are the five subunits that make up the RNA polymerase core enzyme?

Answer 22

1. Two identical alpha subunits
2. One beta subunit
3. One beta prime subunit
4. Omega subunit

Question 23

What two components make up the RNA polymerase holoenzyme?

Answer 23

RNA polymerase core enzyme + sigma factor

Question 24

What are the three polymerases in eukaryotes? What class of RNAs do each transcribe?

Answer 24

1. RNA polymerase I - most ribosomal RNA genes
2. RNA polymerase II - all protein-encoding genes
3. RNA polymerase III - tRNA genes, some snRNA, and other small RNA genes

Question 25

Which RNA polymerase has a carboxy-terminal domain?

Answer 25

RNA Pol II

Question 26

What is the function of the carboxy-terminal domain on RNA polymerase II?

Answer 26

Serves as a binding site for transcription factors

Question 27

The binding of transcription factors to the carboxy-terminal domain depends on ____________.

Answer 27

Phosphorylation

Question 28

?

Question 29

RNA splicing removes _____ and attaches ______ together.

Answer 29

Introns; exons

Question 30

_______ catalyzes RNA splicing.

Answer 30

Spliceosome

Question 31

What is a spliceosome?

Answer 31

Large assembly of small nuclear ribonucleoproteins (snRNPs)

Question 32

What are snRNPs made up of?

Answer 32

1. Small nuclear RNAs 2. Proteins

Question 33

What are the five snRNPs that make up the spliceosome?

Answer 33

U1, U2, U4, U5, U6

Question 34

Explain the process of RNA splicing. What does each snRNP do?

Answer 34

1. U1 binds 5’ splice site 2. Proteins recognize branch point A. Proteins later replaced by U2 3. Complex of U4/U6 and U5 binds to 5’ splice junction and assists in bringing 5’ end to branch point A 4. 1st transesterification reaction - reaction between branch point A and 5’ splice site creates a lariat 5. 2nd transesterification reaction - reaction between 3’ end of upstream exon and 5’ of next exon (cleaves of intron)

Question 35

Nuclear pore complexes are composed of what class of proteins?

Answer 35

Nuceoporins

Question 36

Describe the structure of an NPC.

Answer 36

Hollow, cylindrical structure

Question 37

What does a nuclear transport receptor do?

Answer 37

Associates with mRNA to help it pass through NPC

Question 38

List the types of junk RNAs in a cell.

Answer 38

1. Pre-spliced mRNA 2. Excised introns 3. Incompletely spliced products

Question 39

List the proteins that mRNA associates with.

Answer 39

1. Cap Binding Complex (CBC) 2. Exon Junction Complex (EJC) 3. Poly-A-binding proteins 4. Heterogenous nuclear RiboNuclear Proteins (hnRNPs) 5. SR proteins

Question 40

Which protein associated with 5’ cap?

Answer 40

Cap binding complex (CBC)

Question 41

Which proteins associate with Poly-A tail?

Answer 41

Poly-A-binding proteins

Question 42

Why are junk RNAs unable to pass the NPC?

Answer 42

Junk RNAs cannot bind to proteins that associate with mRNA and as a result remain stalled Cell can distinguish between correctly processed mRNA by detecting the proteins associated with RNA

Question 43

Describe the RNA exosome. What is the function and structure?

Answer 43

• Degrades junk RNAs • RNA protein complex comprised of a barrel-shaped core

Question 44

What type of activity does the RNA exosome have?

Answer 44

Exonuclease