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MCB2050 > e. LEC 1 + 2 Slide Deck > Flashcards

e. LEC 1 + 2 Slide Deck Flashcards

1
Q

Which enzyme regulates gene expression in prokaryotes? Is this the same in Eukaryotes?

A

a) RNA polymerase
b) No in eukaryotes have three different kinds of RNA Polymerases

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2
Q

What are the 3 elements that help initiate transcription of the RNA polymerase in prokaryotes? Describe each.

A
  1. -35/-30 = where the sigma-factor associates w/ the DNA
  2. -10 = where the RNA pol binds to DNA
  3. +1 (start site) = where transcription starts
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3
Q

In prokaryotes, there are proteins called sigma-factors that are used to load the RNA polymerase onto the start site. What are these promoters called in eukaryotes?

A

GTF = general transcription factors

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4
Q

What 2 proteins regulate the start and stop of transcription? Indicate which one does what.

A
  1. activator = start
  2. repressor = stop
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5
Q

What proteins regulate

the activator/repressor? provide an example.

A

the operon for example the lac operon in which the [lac] regulates transcription.

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6
Q

How does the activator encourages transcription and the repressor discourage it?

A
  1. Activator = binds to the promoter protein
  2. repressor = winds the DNA to prevent the RNA pol from transcribing it
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7
Q

Which type of operon is used during prokaryotic transcription initiation vs elongation? How does [high] vs [low] of each affect the activators and repressors?

A

initiation = lac operon
a) high [lac] = repression of transcription
b) low [lac] = activation of transcription

elongation = trp operon
a) high [trp]= repression of transcription
b) low [trp] = activation of transcription

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8
Q

What is the purpose of gene control in Eukaryotes?

A

to make sure that the proper genes are being expressed in the proper cells at the proper time

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9
Q

T or F - unlike prokaryotes eukaryotes transcribe DNA that has been wrapped into chromatin

A

F - While DNA in eukaryotes are packaged in chromatin there needs to be a mech to open that chromatin in order to allow for those genes to be activated/transcribed

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10
Q

T or F - single cellular eukaryotic organisms exist

A

T - yeast is a great example of this

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11
Q

Describe a nucleosome

A

DNA wrapped around a histone protein

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12
Q

Describe epigenetic regulation

A

this is the regulation of DNA caused by changes in the environment.

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13
Q

T or F - while epigenetic markers can change the expression of certain genes as a result of exogenous changes it cannot be inherited as the DNA itself remains the same.

A

F - it can be inherited

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14
Q

Describe the difference b/w euchromatin and heterochromatin

A
  1. E = where genes are unwound and active
  2. H = where genes are tightly wound and inactive
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15
Q

When staining a eukaryotic cell it shows that heterochromatin is darker than euchromatin. Why is this?

A

This is b/c heterochromatin is densely packaged DNA that is rich in transposons, centromeres, and telomeres.

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16
Q

Describe the following terms wrt heterochromatin
a) transposons
b) centromeres
c) telomeres

A

a) repetitive non-coding DNA
b) pt where two chromosomes are attached
c) the protective ends of chromosomes

17
Q

Fill in the blanks for this RNA chart

A
18
Q

What are the 2 main subunits for prokaryotic RNA polymerases? Eukaryotic Pol? What is the purpose of these subunits?

A

Prokaryotes = beta + beta prime (B and B’)
Eukaryotes = RPB1 + RPB2
These subunits help load the RNA pol onto the DNA and provide it a channel for the transcribed RNA to escape.

19
Q

Describe the fxn of subunit RPB1 in eukaryotic RNA pols

A

this subunit is the clamp domain of the Pol. It allows the RNA pol to latch onto the DNA and is then closed by a bridge

20
Q

Describe homology

A

similarity

21
Q

In eukaryotes, scientists have attempted to crystalize all three types of RNA pol however it was found that Pol II was too unstable to do so. ANS the following questions wrt this instability’
a) What is the name of the domain that is making pol II so unstable
b) What subunit is this domain in RPB1 or RPB2
c) Name the 7 AAs that encode this domain.

A

a) Carboxy-terminal domain = CTD
b) RPB2
c) Tyr-Ser-Pro-Thr-Ser-Pro-Ser (YSPTSPS)

22
Q

T or F - the sequence that encodes CTD in eukaryotes repeats a total of 52 times.

A

F - it repeats 26 times for all eukaryotes except mammals in which it repeats 52 times

23
Q

Name the sequence of 7AA’s that encode the CTD. Which one of the AA’s mentioned is special? how?

A

Tyr-Ser-Pro-Thr-Ser-Pro-Ser
Ser is special b/c it is phosphorylated when the transcription phases transition from the initiation phase to the elongation phase

24
Q

What are the common features among all sequences of 7 AA’s w/in the CTD? Explain.

A

All the AA can be phosphorylated easily. This means it can gain a phosphate group from an ATP as a means of gaining NRG

25
Q

Which of the RNA pol’s is the most tightly regulated? Why?

A

Pol II b/c it transcribes the most important types of RNA such as mRNA which encodes all proteins.

26
Q

T or F - Ca2+ is needed for the RNA pol’s in eukaryotes to fxn

A

F - it is Mg2+ that is needed and only for RNA pol II

27
Q

What are the 4 positions of the core promotor elements? Include the name and approx position. Which position has the most wobble?

A
  1. BRE = TFIIB recognition element (-37 to -32)
  2. TATA box (-31 to -26)
  3. Inr = initiator (-2 to +4) - most wobble
  4. DPE = downstream promoter element (+28 to +32)
28
Q

What does TFIIB stand for? Are they associated w/ prokaryotes or eukaryotes?

A

Transcription factor, Pol II, subunit RPB1. They are eukaryotic

29
Q

when an element position is referred to as having a lot of wobble what does this mean?

A

the sequence used for that element varies a lot and is the hardest to identify

30
Q

T or F - all genes contain a TATA box as this sequence is needed to position the Pol II onto the DNA

A

F - most but not all genes have the TATA box

31
Q

What are the 4 factors that help the RNA pol II recognize and bind to the DNA b/f transcription can take place? Which factor is the most prevalent?

A
  1. GIITFs = general Pol II transcription factors = help assemble preinitiation complex over core promoter sequence of DNA - most prevalent
  2. DNA helicase = unwind DNAm to make it accessible
  3. protein kinase
  4. factors that help move the nucleosomes temporarily
32
Q

What are all the GTFs for the following;
a) RNA pol I - 2
b) RNA pol II - 5 (which is the most prevalent?)
c) RNA pol III - 2

A

a) TFIA + TFIB
b) TFIIA, TFIIB (most prevalent), TFIID, TFIIE, TFIIH
c) TFIIIB + TFIIIS

MCB2050 (18 decks)

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