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Molecular Genetics > Quiz 04/13/23 > Flashcards

Quiz 04/13/23 Flashcards

1
Q

what does the trp operon encode?

A

enzymes that are involved with the biosynthesis of tryptophan

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2
Q

trp is a _________ operon, which means it can be repressed by the presence of a particular substance

A

repressible

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3
Q

How many continuous structural genes are in a trp operon and what are they?

A
  1. 5
  2. TrpE, D, C, B, and A gene
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4
Q

Structural genes of a trp operon transcribe what type of mRNA?

A

Polycistronic mRNA

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5
Q

What enzyme is created from the genes of the trp operon?

A

tryptophansythetase

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6
Q

What are the regulatory and repressor genes of the trp operon? (4 total)

A
  1. Promoter region (P)
  2. Operator region (O)
  3. trpL gene
  4. Attenuator region
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7
Q

What are the functions of the trpL gene of the trp operon?

A
  1. Encodes leader peptide (14 amino acids)
  2. The mRNA determines the transcription and translation of the trp operon
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8
Q

What is the function of the attenuator region of the trp operon?

A

When tryptophan is present, the attenuator region of the trp operon encodes immature transcription

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9
Q

What is the function of the trpR gene? (which is upstream of the trp operon)

A

It produces repressors that bind to the operator region

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10
Q

Summarize the trp operon model (hint: talk about tryptophan)

A
  1. The presence of tryptophan determines whether or not the gene is expressed
    a. No/low tryptophan, repressor is inactive, can’t bind to operator region –> gene is expressed
    b. Tryptophan present, repressor is active, repressor binds to operator region –> gene is NOT expressed
    -Also, when present, attenuation occurs and a stem-loop is formed, causing premature termination of transcription
    -Charged trp-tRNA present
    -Production of tryptophan is stopped
    -INCOMPLETE CARD
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11
Q

In an operon, catabolic verses anabolic genes are usually regulated in what kind of manner?

A
  1. Catabolic- inducible manner
  2. anabolic- repressible manner
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12
Q

The majority of gene regulation in bacteria is at a ___________ level

A

transcriptional, although posttranslational is also possible

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13
Q

In translational regulation, the repressors have three characteristics. What are they?

A

Repressors:
1. Have sequence within mRNA
2. May bind to Shine-Dalgarno sequence
3. Binding may cause structural change on mRNA

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14
Q

In translational regulation, the antisense RNA is…

A
  1. complementary to mRNA
  2. does osmoregulation in E. coli
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15
Q

Which gene in the osmoregulation of E. coli forms porins on the outer membrane of E. coli?

A

ompF gene

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16
Q

What do porins control?

A
  1. Osmotic pressure of the cell
17
Q

What do proin plugs do?

A

Keep solutes from going INTO the cell

18
Q

Which gene inhibits porin formation?

A

micF gene

19
Q

What type of condition outside the cell allows for the solutes to flow inside the cell?

A

hypotonic condition

20
Q

The RNA of the micF gene is antisense to which mRNA?

A

ompF mRNA

21
Q

Does the micF gene produce protein?

A

No

22
Q

What are the 4 points in feedback inhibition during post-translational regulation?

A
  1. The final product of the pathway inhibits activity of one or more enzymes of the pathway
  2. The enzymes have a regulatory, allosteric, and a catalytic site
  3. The binding of the final product to regulatory site changes shape of enzyme
  4. The enzyme cannot bind to substrate
23
Q

During post-translational regulation, the covalent modification of enzymes are done in which three ways? And which modifications are reversible?

A
  1. Modification may include:
    a.) proteolytic processing
    b.) disulfide processing
    c.) attachment of sugars, functional groups, or lipids
  2. Reversible modifications are:
    a.) phosphorylation
    b.) acetylation
    c.) methylation
24
Q

What year were riboswitches discovered?

A

2001 and 2002

25
Q

A riboswitch can mediate RNA function. How?

A

A small molecule binds to a regulatory segment of mRNA, which causes conformational change, which leads to the change of mRNA function

26
Q

Riboswitches of mRNA regulates its own _____________ and ________________

A

translational activity, enzymatic activity

27
Q

What organisms are riboswitches found in?

A

Bacteria, archaea, algae, fungi, plants

28
Q

What are the types of riboswitches (Table 14.2)

A

Table 14.2

ADD IMAGE
ESSAY QUESTION

29
Q

During transcription of riboswitches, what type of hairpins are formed?

A

rho-independent transcription termination hairpins

30
Q

Regulation of transcription and translation via riboswitches is governed by which compound?

A

Thiamin pyrophosphate (TTP)

31
Q

What is Thiamin pyrophosphate (TTP)?

A

An essential coenzyme for the functioning of various enzymes
-Also called vitamin B

32
Q

Describe the transcriptional control of thi operon of B. subtilis bacteria (HINT: Talk about TTP/VIT B)

A

-When TPP is LOW, ‘terminator step loop’ cant form because of the formation of a secondary structure called ‘antiterminator’ prevents termination, which completes transcription.

-When TPP is HIGH, TPP will bind to the thi operon mRNA that is being transcribed, which causes the mRNA to change it’s secondary structure, forming a ‘terminator stem loop’, which stops transcription.

33
Q

Describe the translational control of thiMD operon in E. coli. (HINT: TPP) Also, how many enzymes are encoded and what is their purpose?

A
  1. When TPP levels are LOW, the 5’ end of mRNA folds into a secondary structure, the Shine-Dalgarno sequence is accessible to ribosomes, and translation is completed.
    -When TPP levels are high, TPP binds to the 5’ end of the mRNA and causes a change in the secondary structure. The Shine-Dalgarno sequence is no longer accessible to the ribosome and translation is stopped
  2. Two enzymes are encoded and are involved with TPP biosynthesis

Molecular Genetics (5 decks)

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