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Molecules to Cells - Genetics and Virology > Lecture 26. Gene Expression in Prokaryotes and Eukaryotes > Flashcards

Lecture 26. Gene Expression in Prokaryotes and Eukaryotes Flashcards

1
Q

What produces distinct cell types ?

A

Differential gene expression patterns

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2
Q

Why in eukaryotes is the cell under complex control ?

A

They contain many different cell types and what makes one cell type different from another is the specific cohort of genes that each cell expresses

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3
Q

What are some cellular activities ?

A
  1. During cell division
  2. In response to stimulation with glucose
  3. In response to stress or starvation
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4
Q

What is gene expression fundamental to ?

A

What an organism can do and whether it can adapt to changing circumstances

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5
Q

Where do different cell types arrive ?

A

Embryonic development

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6
Q

What initiates different patterns of gene expression ?

A

Developmental signals

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7
Q

When can cell differentiation occur ?

A

Occurs during multiple stages of development including in the adult

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8
Q

What are the cells in the early embryo called ?

A

Blastomere

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9
Q

What types of cells do cells in the early embryo begin as ?

A

Totipotent

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10
Q

What are totipotent cells ?

A

Can differentiate into any cell type

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11
Q

In response to signals, what do cells that are totipotent differentiate into ?

A

Pluripotent, multipotent and finally fully differentiated cells

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12
Q

What are housekeeping genes ?

A

Genes that are expressed in practically all cells within a given organism

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13
Q

What do housekeeping genes include ?

A

RNA and proteins that are required to build common cellular structures, organelles and carry out basic functions of the cell

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14
Q

What are some types of housekeeping genes ?

A
  1. Structural proteins
  2. Enzymes for cellular metabolism
  3. Proteins and other enzymes for organelle synthesis and maintenance
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15
Q

What are tissue-specific genes ?

A

Genes which are relatively unique to each cell type

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16
Q

Where are tissue specific genes expressed ?

A

Specific cell types

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17
Q

What are the four mechanisms of different patterns of gene expression ?

A
  1. Transcriptional
  2. Post-transcriptional
  3. Translational
  4. Post translational
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18
Q

What does the transcriptional mechanism involve ?

A

Factors that affect RNA transcription

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19
Q

What does the post-transcriptional mechanism involve ?

A

Factors that affect stability or composition of RNAs

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20
Q

What does the translational mechanism involve ?

A

Factors that affect translation of mRNAs into protein

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21
Q

What does the post-transcriptional mechanism involve ?

A

Factors that affect protein function of activity state

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22
Q

What does RNA polymerase regulate RNA synthesis in tandem with ?

A

Transcription activators and repressors

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23
Q

At its most basic level, how is gene expression regulated ?

A

Through binding of an RNA polymerase to the regulatory elements upstream of a gene

24
Q

What is found close to the transcription start sites of most genes ?

A

Specific DNA sequences

25
Q

In prokaryotes, how many RNA polymerases are utilised ?

A

1

26
Q

In eukaryotes, how many RNA polymerases are utilised ?

A

3

27
Q

What is e. coli RNA polymerase comprise of ?

A

2 alpha subunits, 1 beta, 1 beta prime, 1 omega and 1 sigma

28
Q

What is the function of the sigma subunit in e.coli RNA polymerase ?

A

Recognizes the specific sequences that are common in bacteria promoters and help to position the RNA polymerase at the right place upstream of the transcriptional start site of the gene

29
Q

In bacterial promoters, where do the common sequence elements begin ?

A

The TATA box and the TTGACAT

30
Q

Where is the TATA box ?

A
  • 10 base pairs
31
Q

Where is the TTGACAT ?

A
  • 35 base pairs
32
Q

What is another name of the TATA box ?

A

Pribnow box

33
Q

What are the TATA box and the TTGACAT recognised by ?

A

RNA polymerase specifically the sigma subunit

34
Q

What is the function of the sigma subunit in bacterial promoters (generally) ?

A

Positions the polymerase at the correct position to initiate transcription and also separates the strands of double helix apart to enable transcription to begin

35
Q

Upon initiation of transcription, what happens to the sigma subunit ?

A

It dissociates from the promoter

36
Q

What happens in chain termination ?

A

RNA polymerase recognises specific sequences within DNA that act to terminate RNA synthesis

37
Q

What do the sequences which act to terminate RNA synthesis form ?

A

Hairpins which form in the growing RNA molecules

38
Q

What is intrinsic termination sequences ?

A

Sequences which terminate RNA synthesis cause hairpins to form in a growing RNA molecule that causes it to fall off the DNA template

39
Q

What can a protein called Rho do ?

A

Can recognize certain sequence elements that are also termination signals and upon binding to these elements can the bind to RNA polymerase causing it to fall off the DNA and release the RNA

40
Q

What is Rho-dependent termination ?

A

Requires Rho to bind to RNA polymerase causing it to fall off the DNA and release the RNA

41
Q

What is the function of transcriptional repressors ?

A

Work by sitting on or close to the promoter regions of the DNA, preventing RNA polymerase or initiator/activator proteins from starting transcription initiation therefore turning off the genes

42
Q

In prokaryotes are promoters usually on or off ?

A

Constitutively on

43
Q

In a prokaryote, what stops the gene promotors from being constitutively on ?

A

The binding or activity of RNA polymerase being blocked or impeded by binding of a transcriptional repressor to the promoter

44
Q

What is the function of the lac repressor ?

A

Represses the genes that are involved in lactose utilisation in bacteria

45
Q

What are bacterial genes often co-transcribed within ?

A

Operons

46
Q

What is an operon ?

A

Groups of related genes that are co-transcribed under the control of the same repressor and promoter

47
Q

What type of genes are often in operons ?

A

Bacterial genes

48
Q

Why are bacterial genes organised into operons ?

A

They live in harsh and ever changing environments where food sources vary rapidly, requiring the bacterium to be able to rapidly express new sets of genes that are required to deal with varying food sources

49
Q

What is the lac operon controlled by ?

A

Lac repressor protein

50
Q

What three enzymes does the growth on lactose depend on ?

A
  1. B-galactoside
  2. Permease
  3. Thiogalactoside transacetylase
51
Q

What are some characteristics of the genes that encode the enzymes B-galactosidase, permease and thiogalactoside transacetylase

A
  1. The three genes were tightly linked on the chromosome
  2. All were induced coordinately
  3. The ratio of Lac Z:A:Y proteins remain constant
52
Q

How does the lac operon work ?

A
  1. lacI encodes a repressor LacI that switches off the whole operon in the absence of lactose (by binding to the operator for the Lac Operon)
  2. When lactose is present, this binds to the Lacl repressor protein and displaces it from the promoter, permitting the Lac Operon to switch on and express the genes required for lactose utilisation
53
Q

What are the genes required for lactose utilisation ?

A
  1. LacZ
  2. LacA
  3. LacY
54
Q

What proteins are considered as stable ?

A

Keratin, secreting proteins

55
Q

What proteins are considered as short lived or unstable ?

A

Transcription factors

Molecules to Cells - Genetics and Virology (16 decks)

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