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bio exam > Unit 3 - Gene Expression > Flashcards

Unit 3 - Gene Expression Flashcards

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Biology 101 flashcards
1
Q

Gene regulation

A

involves turning genes on or off depending on their products r required

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2
Q

Regulators (2) types

A

r the proteins that switch genes on or of:
1) activators (gene on)
2) repressors (gene off)

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3
Q

Housekeeping genes

A

ALWAYS NEEDED
- constantly being transcribed/ translated (ssbp)
- most genes r not HK genes

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4
Q

Transcription

A

in the nucleus = product mRNA

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5
Q

Translation

A

in the cytoplasm = product protein

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6
Q

4 levels of control in gene expression

A

1) transcriptional
(mRNA being synthesized)
2) posttranscripional
(mRNA being made)
3) translational
( protein being synthesized)
4) posttranslational
(after protein has been synthesized

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7
Q

Transcriptional regulation

A
  • regulation of which genes r transcribed
  • can involve cortrol of the rate t occurs
    a) controlling chromatin structure
    b) enhancer regions on DNA
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8
Q

Chromatin Accessinilty

A

the structure of chromatin (DNA and its organizing proteins) can be regulated. More open or relaxed chromatin makes a gene more available for transcription (+ of acetyl group to histones loosens their association w DNA and promoter bc accessible)

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9
Q

Methylation transcriptional regulation

A

a methyl group is + to the cytosine bases in the promoter of a gene inhibiting transcription This silences the genes for a period of time

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10
Q

bone marrow

A

produce red blood cells, use specific enzyme to remove methyl group and allow transcription

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11
Q

Alternative splicing

A

perhaps 75% of human gens r alternatively splices at the pre-mRNA level

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12
Q

binding masking proteins to mRNA

A

when the mRNA is associated w a masking protein it does not undergo protein synthesis

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13
Q

regulation changes the rate of degradation of mRNAs

A

-regulatory mols such as a hormone, will directly or indirectly affect the rate of mRNA breakdown
ie. mammary gland of a rate it takes 5h for half of the mRNA for milk protein to break down and in the presence of the hormone prolactin time increases to 92h

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14
Q

mRNA transcription r translated into proteins

A

ie. length of Poly A tail increases or decreases how long translation take place but scientists r not really sure how this works

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15
Q

Posttranslational Regulation

A

controls when proteins bc fully functional, how long they r functional and there degradation (modifications made to the polypeptide chain)
ie. proteins go from inactive to active from processing mechansims (special chemical group can be added or removed from protein )

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16
Q

Prokarytotic; gene regulation

A

gene expression in P is regulated in response to the concentration of two mols:
- lactose
- tryptophan

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17
Q

Lac operon vs Trp operon

A

both - feedback
lac = uses a single mol (lactose ) that induces the expression of operon genes
trp = a single mol of (tryptophan) that represses the expression of the operon genes

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18
Q

Operon in prokaryotes

A

a cluster of genses under the contril of one set of regulatroy sequence

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19
Q

regulatory sequence (2)

A

1) promoter = the site where DNA transcription begins
2) operator = the sequence of bases that control transcription

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20
Q

Strucural genes

A

coding regions which code for the specific proteins

21
Q

Operator sequence

A

regulator protein binds
- depending on the regulator, binding to the operator causes either activation transciption or repression transcription

22
Q

effector of operator (3)

A

1) acts on the regulator protein
2) can be an inducer (stimulates)
3) can be a corepressor (inhibits)

23
Q

Lac Operon (-) regulation

A

the sugar lactose, a potential source of energy from prokaryotes must be acquired directly from the environment. required for lactose metabolism, prokaryotes use lac operon

24
Q

Lac Operon (3)

A

1) lactose = glucose + galactose
2) dissacharide in milk
3) e.coli: b-galactoside catalyses the cleavage of the bond in lactose

25
Q

structure of lac operon

A

cluster of genes: lacZ, lacy, lacA
- each codes a different part of the enzyme
- all r under the control of one promoter

26
Q

lacoste absent

A

negative control mechanism prevents production of B-galactosidase

27
Q

Lacl Protein

A

repressor protein; blocks transcription of the lac (physical blockage; covers part of lac promoter)

28
Q

mechanism of regulation (1) lac

A

when lactose is not present in the cell environment, the lacl protein binds to the lac operator coverint part of the promoter blocking transcription

29
Q

mechanism of regulation (2) lac

A

lactose binds to the Lacl protein, changing its shape, it can no longer bing to the lac operator and transcription proceeds

30
Q

Lactose absent

A

= no transcription

31
Q

Lactose is present

A
  • lactose binds to Lacl protein
  • Lacl changes conformation = unable to bind to lac operator
  • RNA polymerase can access lac promoter
  • transcription occurs
32
Q

what is the effector mol

A

inducer

33
Q

Inducer

A

a single mol that triggers the expression of an operon’s genes by deactivating the repressor protien

34
Q

(-) control

A

transcription is off, due to binding of a repressor protein
- presence of an effector (inducer) removes the repress form operator region
transcription can now occur

35
Q

Trp Operon (+) regulation

A

tryptophan is an important aa that is used to build proteins. Most prokaryotic cells are able to synthesize tryptophan independently, but they can also take it up directly if it is available in the environment. The operon that regulates the production of tryptophan in a cell is called trp operon

36
Q

operon in trp + transcription

A

cluster of 5 genes encoding enzymes required for trp synthesis and transcription of operon is repressed when concentrations of trp in the cell r high

37
Q

why is trp +

A

positive control mechanism prevents production of tryptophan, if tryptophan levels r high

38
Q

Mechanism of regulation (1) trp

A

lack of tryptophan inactivates the repressor and transcription proceeds

39
Q

Mechanism of regulation (2) trp

A

tryptophan acts as a corepressor and binds to the tryptophan repressor. the complex can now bind to the trp operator and transcription is blocked.

40
Q

trp absent

A

trp operon is transcribed (default)

41
Q

trp present

A
  • trp itself will bind to the repressor protein
  • conformational shape occurs
  • allows repressor to bind to the trp operator = shuts off transcription
42
Q

effector mol of trp

A

corepressor

43
Q

corepressor

A

it binds to a repressor to activate it in order to repress transcription

44
Q

positive control

A

transcription is on so presence of an effector (co-repressor) cause binding of the repressor to the operator so transcription does not occur

45
Q

Positive vs Negative control

A

+ = transcription on allows the repressor to bind
- = transcription is off so removes repressor

46
Q

Gene Regulation

A

describes any process that alters the rate of gene expression

47
Q

operon

A

a cluster of closely related genes. they are all controlled by one set of regulatory sequences

48
Q

promoter

A

DNA sequence to which RNA polymerase binds to being transcription

49
Q

operator regulatory DNA sequence

A

DNA sequence to which a transcription factor binds in order to alter transcription = close to the promoter

bio exam (41 decks)

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