Exam 2 Review

Question 1

What does the sigma factor in prokaryotic cells do?

Answer 1

• binds the -10 region of the promotor
• recruits the core RNA polymerase holoenzyme
• polymerizes RNA in a 5’-> 3’

Question 2

What would deletion of the -10 sequence in the prokaryotic promotor immediately affect?

Answer 2

transcription

Question 3

What is the first protein to bind DNA and initiate transcription of a eukaryotic gene?

Answer 3

TBP (TATA binding protein)

Question 4

In eukaryotes, the ______ is a sequence that can activate transcription from 50,000bp away.

Answer 4

enhancer

Question 5

What is not a function of the 5’-methylguanine cap?

Answer 5

splicing

Question 6

What is universal, degenerate, and decoded by tRNA molecules?

Answer 6

The Genetic Code

Question 7

What would happen in aminoacyl-tRNA synthetase enzyme was mutated and did not carry out its function?

Answer 7

wrong amino acids would be incorporated into a peptide

Question 8

What are ribosomes composed of?

Answer 8

protein and rRNAs

Question 9

Why is a single tRNA sometimes able to decode more than one codon?

Answer 9

wobble base pairing at the third nucleotide of the codon

Question 10

Examples of regulatory DNA sequences.

Answer 10

silence, enhancer, promoter

Question 11

T or F , sigma factor is required for initiation.

Answer 11

True

Question 12

T or F, nucleotides are always added to the 3’ end of the elongating mRNA

Answer 12

true

Question 13

T or F, for one gene, either strand of the DNA helix can be the template strand.

Answer 13

False

Question 14

T or F, Co-transcriptional translation can occur.

Answer 14

True

Question 15

T or F, termination occurs when the RNA polymerase reaches the stop codon.

Answer 15

false

Question 16

True or False, RNA polymerase needs a primer to begin synthesis.

Answer 16

False

Question 17

What are the steps of a spliceosome removal of an intron.

Answer 17

1. mRNA cut at 5’ splice site of intron
2. 5’ of intron attaches to Branchpoint-A
3. cut made at 3’ splice site of intron
4. intron released as a lariat and degraded
5. two exons are spliced together by spliceosome
6. spliced mRNA transported to cytoplasm

Question 18

How does the spliceosome identify the intron sequences to remove?

Answer 18

The spliceosome recognizes the consensus sequences at the intron/exon boundary.

Question 19

The start codon in prokaryotes and eukaryotes is _____.

Answer 19

AUG

Question 20

The shine-delgarno sequence is part of the ______ sequence just _______ of AUG.

Answer 20

mRNA; upstream

Question 21

To translate a mRNA, two other types of RNAs are required; ______ and _____.

Answer 21

tRNA and rRNA

Question 22

______ and _______ are examples of consensus sequences , or sequences that are similar across multiple genes, or mRNA, to insure the same outcome.

Answer 22

Promoter and Terminator

Question 23

Ribosomes form _______ bonds between amino acids during translation.

Answer 23

peptide

Question 24

The Dicer enzyme cleaves _______ into ____#nt fragments that regulate gene expression.

Answer 24

dsRNA; 21

Question 25

Describe two ways prokaryotes terminate transcription.

Answer 25

The first way prokaryotes terminate transcription is with Rho-dependent termination. In Rho-dependent termination, Rho fonds and attaches to the rut site on the RNA and travels up the RNA until it reaches RNA polymerase then it stops RNA pol by unwinding the strand of RNA and DNA.

The second way is with Rho-independent termination. In Rho-independent termination, the inverted repeats in the RNA base pair and form a hair pin loop. The weak AU base pairs causes RNA polymerase to destabilize and let go.

Question 26

What are the steps of prokaryotic translation initiation.

Answer 26

1. IF3 binds small ribosome subunit separating it from the large subunit.
2. small ribosome binds Shine-Delgarno sequence on mRNA
3. initiator f-Met + IF1 +IF2 +GTP complex basepairs with start codon.
4. large ribosome subunit binds.
5. f-met tRNA is base paired with mRNA in p-site
6. IF1, IF2, IF3 disassociates from ribosome and tRNA.

Question 27

Describe the process of translation elongation and termination in a prokaryotic cell starting after the large subunit binds.

Answer 27

• Fmet tRNA in p site
• EF-Tu w/ GTP bind next tRNA and bring it to A-site (anticodon bp)
• GTP hydrolyzed to GDP and EF-Tu disassociates (Efts recycles EFtu +GTP)
• Peptide bond between Met-AA2 catalyzed by ribosome (rRNA)(2OH-)
• Ribosome translocates 1 codon w/ EF-G +GTP; Fmet tRNA in E site
• uncharged tRNA exits

Question 28

List the 6 levels of gene expression control. Choose two levels and give an example of regulation.

Answer 28

1. Chromatin packaging
2. Transcription
3. mRNA processing
4. mRNA stability
5. translational
6. post-translational modification

Question 29

Example of Chromatin packaging.

Answer 29

if chromatin is heterochromatin it can’t be transcribed. It can only be transcribed if it is euchromatin.

Question 30

Example of post translational modification.

Answer 30

ubiquination; adding a ubiquitin to a protein so that the protein will be sent to the proteasome for degradation.

Question 31

Why is control of gene expression so important in multicellular organisms like humans?

Answer 31

Control of gene expression in humans allows us to have cells with different jobs and functions based off of which of their genes are being expression/ turned on.

Question 32

Describe secondary protein structure.

Answer 32

chain of amino acids either folded into an alpha helix or a beta sheet.

Question 33

Describe tertiary protein structure.

Answer 33

secondary structure folded into a 3D globular shape such as a beta barrel; forms a protein.

Question 34

Describe quaternary protein structure.

Answer 34

more than one protein working together for a function.

Question 35

Glycolyisization

Answer 35

adding a glucose molecule to a protein which makes it slippery and allows cells to slide past each other