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Genetics > Chapter 16 > Flashcards

Chapter 16 Flashcards

1
Q

Genes that are continually expressed and not regulated are called…

A

Constitutive, continually expressed under normal conditions

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2
Q

Genes that encode proteins (metabolism/biosynthesis)

A

Structural genes

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3
Q

Genes that encode RNA/proteins (TRANSCRIPTION?TRANSLATION)(interact with DNA)

A

Regulatory genes

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4
Q

Untranscribed DNA sequences that affect the expression of DNA sequences to which they are physically linked.

A

Regulatory Elements

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5
Q

Positive control

A

stimulate gene expression

Operon: RP activates transcription

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6
Q

Negative control

A

inhibit gene expression

Operon: RP inhibits transcription

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7
Q

DNA-binding Domains

A

~60-90 amino acids
Responsible for binding to DNA, forming hydrogen bonds with DNA.

Typically only 1 DNA binding domain

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8
Q

Motif

A

within binding domain, simple structure that fits into major groove of DNA

Distinctive types of DNA binding proteins based on the motif

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9
Q

Types of Motifs
Prokaryotes
Eukaryotes

A

Pro: Helix-Turn-Helix (bind to different regulatory proteins)

Eukaryotes: Zinc Fingers (recognizes different sets of DNA sequences), Leucine Zipper

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10
Q

Helix turn Helix

A

2 alpha helices

Major Groove

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11
Q

Zinc-finger

A

Loop of amino acids with zinc at base

Major Groove

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12
Q

Leucine-Zipper

A

Helix of leucine and a basic arm; two leucines interdigitate

Two adjacent major grooves

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13
Q

How do amino acids in DNA-binding proteins interact with DNA?

a. by forming covalent bonds with DNA base
b. By forming hydrogens bonds with DNA base
c. By forming covalent bonds with sugars

A

B) by forming hydrogen bonds with DNA base

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14
Q

Group of bacterial structural genes transcribed together along with promoter and additional sequences that control transcription

A

Operon

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15
Q

What are parts of operon?

A

Promotor
operator
Additional sequences that control transcription
Structure genes

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16
Q

DNA sequence encoding products that affect operon function, but are not part of the operon. Controls expression of structural genes of the operon by increasing/decreasing transcription.

A

Regulator Gene

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17
Q

Structural vs. Regulator Gene

a. Structural genes are transcribed into mRNA, but regulator genes are not.
b. Structural genes have complex structures; regulator genes have simple structure.
c. Structural genes encode proteins that function in the structure of the cell; regulator genes carry out metabolic reactions.
d. Structural genes encode proteins; regulator genes control the transcription of structural genes.

A

d.

Structural = protein
Regulator= transcription of structural genes
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18
Q

Inducible operons transcription normally__

A

Off

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19
Q

Repressible operons, transcription normally

A

On

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20
Q

Negative Inducible

A

Normally Off because RP is bound

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21
Q

Negative Repressible

A

Normally On, because RP is not bound

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22
Q

Positive Inducible

A

Normally Off, because RP is not bound

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23
Q

Positive Repressible

A

Normally on, because RP is bound

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24
Q

corepressor

A

small molecule that binds to the repressor and makes it capable of binding to the operator to turn off transcription. (- repress)

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25
Q

The lac Operon of E. Coli is a ____ ____ operon involved in lactose metabolism whose inducer is _____.

A

Negative inducible Operon

Inducer: Allolactose

26
Q

Lacl

A

repressor encoding gene

27
Q

lacP

A

operon promoter

28
Q

lacO

A

operon operator

29
Q

Structural Genes of lac:
lacZ
lacY
lacA

A

Z: encodes beta-galactosidase
Y: encodes permease
A: encodes transaceylase

30
Q

Does the repression of lac operon completely shut down transcription?

A

No, there are always a few molecules of the structural genes.

31
Q

____ transports lactose into the cell, and _____ breaks it into glucose, galactose, and allolactose.

A

Permease

Beta-Galactosidase

32
Q

lac operon uses _____ _______: simultaneous synthesis of structural proteins stimulated by a specific molecule: the inducer

A

Coordinate Induction

33
Q

The lac operator overlaps with the 5’ end of what gene?

A

lacZ

34
Q

Partial Diploid

A

Full bacterial chromosome + an extra piece of DNA on F plasmid

35
Q

Structural Gene Mutations: effect structure of enzymes, but not….

A

Regulation of their synthesis

36
Q

Regulator Gene mutations: lacI-

A

Can repress Transcription 24/7 regardless of lactose

However, need 2 copies lacI+ > lacI-

Trans acting.
Thus, if one lacI+, and lactose shows up, we got transcription

37
Q

LacI^s

A

No transcription, even if lactose is present because it binds to both operators.

lacI^s > lacI+

38
Q

Operator mutation: alter DNA sequence so RP can’t bind.

A

lacO^c (constitutive)
lacO^c > lacO+ (cis-acting)

When lacO^c and lacZ+ on the same gene, produced regardless of lactose.

However, when on different ones, only if lactose present.

39
Q

Promoter Mutations: binding of RNA polymerase to the promoter

A

lacP-, cis-acting. None produced in presence or absence of lactose.

40
Q

Catabolite repression: Why prefer glucose?

A

Takes less energy to metabolize.
Repress metabolism of other sugars.

Lac only transcribed when lactose present and glucose is absent

41
Q

Catabolic repression is (positive/negative), activated by ____ bound to ____ which binds upstream of lac gene promoter and increases _____ ____

A

Positive

CAP bound to cAMP

Transcriptional efficiency

42
Q

High cAMP

A

low glucose (and vis versa)

43
Q

How does cAMP-CAP enhance transcription?

A

Bends DNA which in turn facilitates RNA polymerase binding to the promoter.

44
Q

trp Operon of E. Coil
is ___ ___.
5 structural genes convert ___ to tryptophan.

A

negative repressible

Chorismate

45
Q

Attenuation

A

Affects the CONTINUATION of transcription, not initiation. This actions TERMINATES TRANSCRIPTION before reaching structural genes

46
Q

Attenuator

A

Terminates transcription

47
Q

Antiterminator

A

prevents termination

48
Q

High Tryptophan:

5’ UTR and what Happens to trp Operon

A

1+2 and

3+4 hairpin

Terminating transcription prematurely. (Attenuator)

49
Q

Low Tryptophan

5’ UTR and what happens to trp Operon

A

2+3 hairpin which prevents 3+4 binding, transcription continues.

No termination (Antiterminator)

50
Q

Attenutation results when which region so 5’ UTR region pair?

A

3 and 4

51
Q

High Tryptophan

Does ribosome stall at trp codons?
Position of ribosome when region 3 transcribed?

A

No

Covers region 2

52
Q

Low Tryptophan

Does ribosome stall at trp codons?
Position of ribosome when region 3 transcribed?

A

Yes

Covers Region 1

53
Q

Why does attenuation take place?

A

When trp is high, no transcription, but repression never complete. Attenuation reduces another 8 fold to reduce more than 600 fold.

54
Q

Repression vs. Attenuation

A

Repression: cellular levels of tryptophan

Attenuation: number of tRNAs charged with tryptophan

55
Q

Antisense RNA

A

complementary to targeted partial sequence of mRNA

Inhibit mRNA translation

If you want to inhibit transcription, make it complimentary to promoter

56
Q

Riboswitches

A

molecules influence the formation of secondary structure in mRNA

57
Q

Ribozymes

A

mRNA molecules with catalytic activity

58
Q

RNA polymerase binding site for lac operon

A

Promoter

59
Q

trp operon has (positive/negative) regulation

A

Negative

60
Q

At which level of gene regulation does attenuation occur

A

Transcription

Genetics (15 decks)

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