Chapter 7: RNA and Genetic Code

Question 1

In what directions does reverse transcriptase read the template and synthesizes?

Answer 1

Reads template: 3’ -> 5’

Synthesizes template: 5’ -> 3’

Question 2

How many AAs are in humans?

Answer 2

21

Question 3

How many codons do we have?

Answer 3

64

Question 4

What is the benefit of redundancy in the genetic code?

Answer 4

Protects against single nucleotide mutations

Question 5

Where does transcription occur?

Answer 5

Nucleus

Question 6

What is the sense strand?

Answer 6

It is the coding strand or the non-template strand

Question 7

What is the antisense strand?

Answer 7

It is the template strand

Question 8

Where does translation occur?

Answer 8

In the ribosome of the cytosol or RER

Question 9

Which system types or operons control gene expression in prokaryotes?

Answer 9

1. Inducible

2. Repressible

Question 10

What is an example of an inducible system?

Answer 10

Lac operon

Question 11

What is an example of a repressible system?

Answer 11

Trp operon

Question 12

Operon

Answer 12

• Cluster of genes transcribed as a single mRNA.

* Offers on and off switch for gene control

Question 13

Jacob-Monod Model

Answer 13

Is the structure and function of operons

Question 14

Structural gene

Answer 14

Codes for the protein of interest

Question 15

Operator site

Answer 15

• Is upstream of structural gene

* A nontranscribable region of DNA that is capable of binding a repressor protein

Question 16

Promoter site

Answer 16

• Provides a site for RNA polymerase to bind.
• Is similar in function to promoters in eukaryoties.
• More upstream than operator site.

Question 17

Regulator gene

Answer 17

• Codes for repressor protein

* Furthest upstream

Question 18

Inducible Systems

Answer 18

• Repressor is bonded tightly to the operator system and blocks the RNA polymerase from getting from the promoter to the structural gene.
• In order to remove block, inducer must bind to the repressor protein so that RNA polymerase can move down the gene
• Gene products only produced when needed
• inc. [inducer] -> dec. free repressor -> inc. transcription
• Analagous to competitive inhibition.

Question 19

Negative control

Answer 19

Binding of a protein that reduces transcriptional activity

Question 20

Inducer

Answer 20

• Molecule that binds to the repressor protein so that it won’t bind the operator region.
• Allows transcription to occur.

Question 21

Is metabolizing glucose or lactose more energetically expensive?

Answer 21

Lactose

Question 22

In lac operon, what is the inducer molecule?

Answer 22

Lactose

*When lactose is high and glucose low

Question 23

Repressible System

Answer 23

1. Corepressor binds the repressor
2. Repressor-corepressor complex binds to operator site
3. Blocks RNA polymerase from moving along

• Decreases transcription
• Usually exhibits (-) control

Question 24

In a repressible system, the repressor requires what molecule to be active?

Answer 24

Corepressor

Question 25

What molecule binds to CAP when glucose is low?

Answer 25

cAMP binds to CAP

Question 26

How does the trp operon work?

Answer 26

1. 2 molecules of tryptophan (acts as corepressor) bind to repressor 2. Repressor-corepressor complex binds to operator site and blocks RNA polymerase 3. Decreases transcription

Question 27

Transcription factors (TFs) in Eukaryotic Cells

Answer 27

Transcription-activating proteins that search the DNA looking for specific DNA-binding motifs

Question 28

What are the 2 recognizable domains in eukaryotic TFs

Answer 28

1. DNA-binding domain | 2. Activation domain

Question 29

What type of control does the trp operon have?

Answer 29

Negative control

Question 30

How does the trp operon work?

Answer 30

1. 2 molecules of tryptophan (acts as corepressor) bind to repressor 2. Repressor-corepressor complex binds to operator site and blocks RNA polymerase 3. Decreases transcription

Question 31

What does methylation of CpG islands lead to?

Answer 31

* Diminishes the oncogenic potential of cells * Stable silencing of DNA as cells terminally differentiate * Once cells are done differentiating, their DNA needs to be turned off or silenced * CpG methylation silences that DNA of cells that have completed differentiation.

Question 32

Activator

Answer 32

Enhances interaction between the promoter region and RNA polymerase, usually by binding a promoter-proximal element

Question 33

Histone

Answer 33

Structure which condenses DNA into small units

Question 34

DNA response element

Answer 34

sequence of DNA that binds only to specific TFs

Question 35

Role of micro RNA (miRNA)

Answer 35

Causes repression or degradation of the target through mRNA binding

Question 36

Activator

Answer 36

Enhances interaction between the promoter region and RNA polymerase, usually by binding a promoter-proximal element

Question 37

Histone

Answer 37

Structure which condenses DNA into small units

Question 38

Spliceosome

Answer 38

Cuts out introns and ligates the ends.

Question 39

Role of micro RNA (miRNA)

Answer 39

Causes repression or degradation of the target through mRNA binding

Question 40

How can an proto-oncogene be converted to a oncogene?

Answer 40

Gene deletions, chromosomal rearrangements, or gene amplification