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Genetics > Chapter 16 > Flashcards

Chapter 16 Flashcards

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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
The lac Operon of E. Coli is a ____ ____ operon involved in lactose metabolism whose inducer is _____.
Negative inducible Operon Inducer: Allolactose
26
Lacl
repressor encoding gene
27
lacP
operon promoter
28
lacO
operon operator
29
Structural Genes of lac: lacZ lacY lacA
Z: encodes beta-galactosidase Y: encodes permease A: encodes transaceylase
30
Does the repression of lac operon completely shut down transcription?
No, there are always a few molecules of the structural genes.
31
____ transports lactose into the cell, and _____ breaks it into glucose, galactose, and allolactose.
Permease Beta-Galactosidase
32
lac operon uses _____ _______: simultaneous synthesis of structural proteins stimulated by a specific molecule: the inducer
Coordinate Induction
33
The lac operator overlaps with the 5' end of what gene?
lacZ
34
Partial Diploid
Full bacterial chromosome + an extra piece of DNA on F plasmid
35
Structural Gene Mutations: effect structure of enzymes, but not....
Regulation of their synthesis
36
Regulator Gene mutations: lacI-
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
LacI^s
No transcription, even if lactose is present because it binds to both operators. lacI^s > lacI+
38
Operator mutation: alter DNA sequence so RP can't bind.
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
Promoter Mutations: binding of RNA polymerase to the promoter
lacP-, cis-acting. None produced in presence or absence of lactose.
40
Catabolite repression: Why prefer glucose?
Takes less energy to metabolize. Repress metabolism of other sugars. Lac only transcribed when lactose present and glucose is absent
41
Catabolic repression is (positive/negative), activated by ____ bound to ____ which binds upstream of lac gene promoter and increases _____ ____
Positive CAP bound to cAMP Transcriptional efficiency
42
High cAMP
low glucose (and vis versa)
43
How does cAMP-CAP enhance transcription?
Bends DNA which in turn facilitates RNA polymerase binding to the promoter.
44
trp Operon of E. Coil is ___ ___. 5 structural genes convert ___ to tryptophan.
negative repressible Chorismate
45
Attenuation
Affects the CONTINUATION of transcription, not initiation. This actions TERMINATES TRANSCRIPTION before reaching structural genes
46
Attenuator
Terminates transcription
47
Antiterminator
prevents termination
48
High Tryptophan: 5' UTR and what Happens to trp Operon
1+2 and 3+4 hairpin Terminating transcription prematurely. (Attenuator)
49
Low Tryptophan 5' UTR and what happens to trp Operon
2+3 hairpin which prevents 3+4 binding, transcription continues. No termination (Antiterminator)
50
Attenutation results when which region so 5' UTR region pair?
3 and 4
51
High Tryptophan Does ribosome stall at trp codons? Position of ribosome when region 3 transcribed?
No Covers region 2
52
Low Tryptophan Does ribosome stall at trp codons? Position of ribosome when region 3 transcribed?
Yes Covers Region 1
53
Why does attenuation take place?
When trp is high, no transcription, but repression never complete. Attenuation reduces another 8 fold to reduce more than 600 fold.
54
Repression vs. Attenuation
Repression: cellular levels of tryptophan Attenuation: number of tRNAs charged with tryptophan
55
Antisense RNA
complementary to targeted partial sequence of mRNA Inhibit mRNA translation If you want to inhibit transcription, make it complimentary to promoter
56
Riboswitches
molecules influence the formation of secondary structure in mRNA
57
Ribozymes
mRNA molecules with catalytic activity
58
RNA polymerase binding site for lac operon
Promoter
59
trp operon has (positive/negative) regulation
Negative
60
At which level of gene regulation does attenuation occur
Transcription

Genetics (15 decks)

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