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MCAT Biochemistry > Chapter 7: RNA and Genetic Code > Flashcards

Chapter 7: RNA and Genetic Code Flashcards

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MCAT flashcards
1
Q

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

A

Reads template: 3’ -> 5’

Synthesizes template: 5’ -> 3’

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2
Q

How many AAs are in humans?

A

21

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3
Q

How many codons do we have?

A

64

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4
Q

What is the benefit of redundancy in the genetic code?

A

Protects against single nucleotide mutations

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5
Q

Where does transcription occur?

A

Nucleus

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6
Q

What is the sense strand?

A

It is the coding strand or the non-template strand

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7
Q

What is the antisense strand?

A

It is the template strand

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8
Q

Where does translation occur?

A

In the ribosome of the cytosol or RER

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9
Q

Which system types or operons control gene expression in prokaryotes?

A
  1. Inducible

2. Repressible

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10
Q

What is an example of an inducible system?

A

Lac operon

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11
Q

What is an example of a repressible system?

A

Trp operon

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12
Q

Operon

A
  • Cluster of genes transcribed as a single mRNA.

* Offers on and off switch for gene control

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13
Q

Jacob-Monod Model

A

Is the structure and function of operons

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14
Q

Structural gene

A

Codes for the protein of interest

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15
Q

Operator site

A
  • Is upstream of structural gene

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

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16
Q

Promoter site

A
  • Provides a site for RNA polymerase to bind.
  • Is similar in function to promoters in eukaryoties.
  • More upstream than operator site.
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17
Q

Regulator gene

A
  • Codes for repressor protein

* Furthest upstream

18
Q

Inducible Systems

A
  • 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.
19
Q

Negative control

A

Binding of a protein that reduces transcriptional activity

20
Q

Inducer

A
  • Molecule that binds to the repressor protein so that it won’t bind the operator region.
  • Allows transcription to occur.
21
Q

Is metabolizing glucose or lactose more energetically expensive?

A

Lactose

22
Q

In lac operon, what is the inducer molecule?

A

Lactose

*When lactose is high and glucose low

23
Q

Repressible System

A
  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
24
Q

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

A

Corepressor

25
Q

What molecule binds to CAP when glucose is low?

A

cAMP binds to CAP

26
Q

How does the trp operon work?

A
  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
27
Q

Transcription factors (TFs) in Eukaryotic Cells

A

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

28
Q

What are the 2 recognizable domains in eukaryotic TFs

A
  1. DNA-binding domain

2. Activation domain

29
Q

What type of control does the trp operon have?

A

Negative control

30
Q

How does the trp operon work?

A
  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
31
Q

What does methylation of CpG islands lead to?

A
  • 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.
32
Q

Activator

A

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

33
Q

Histone

A

Structure which condenses DNA into small units

34
Q

DNA response element

A

sequence of DNA that binds only to specific TFs

35
Q

Role of micro RNA (miRNA)

A

Causes repression or degradation of the target through mRNA binding

36
Q

Activator

A

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

37
Q

Histone

A

Structure which condenses DNA into small units

38
Q

Spliceosome

A

Cuts out introns and ligates the ends.

39
Q

Role of micro RNA (miRNA)

A

Causes repression or degradation of the target through mRNA binding

40
Q

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

A

Gene deletions, chromosomal rearrangements, or gene amplification

MCAT Biochemistry (7 decks)

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