Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cell Biology > 8. control of gene expression > Flashcards

8. control of gene expression Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

gene expression varies in different cells

A
  • human cells contain ~22,00 genes, but only a fraction of them may be expressed in any one cell
  • some genes are expressed in all cells all the time AKA housekeeping genes responsible for routine metabolic functions common to all cells (eg respiration)
  • some genes are expressed as cell begins to differentiate
  • some genes are expressed only in cells with specialized functions
  • some genes are expressed only when surrounding conditions change (arrival of a hormone)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

regulatory sequence

A

stretches of DNA, which through the action of specific proteins, control the activity/expression of genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are some major contributing factors that makes us different from chimps?

A

differences in how the two species regulate the expression of genes
ie. when where and how much the genes are expressed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

control of gene expression in eukaryotes terms

A

transcription level
processing level
translational level
post-translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

transcription level

A

if and how often a gene is transcribed

transcribed is making RNA using DNA template ( copying the genetic info)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Processing level

A

different messenger RNAs made from a given gene (alternative splicing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

translational level

A

how much of the mRNA is made into protein (and mRNA lifetime)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Post-translation

A

protein lifetime

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

transcriptional control

A

Rna polymerase II transcribes some genes much more frequently than others
- this depends on regulatory sites on the DNA and the presence of transcription factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

RNA polymerase is a complex of ______ different proteins

A

12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

transcription factors

A

DNA binding proteins that regulate transcription

  • they have a DNA binding domain
  • they have an activation domain (a binding site for other proteins)
  • often have a site for binding a second subunit to form a dimer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are three common motifs in transcription factors

A

zinc-finger motif
helix-loop helix
leucine-zipper motif

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

zinc-finger motif

A

multi-finger shaped projections of protein git into major grooves of DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Helix-loop-helix (HLH) motif

A

forms homo and heterodimers; humans have ~120 HLH genes- can produces 1000s of different transcription factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Leucine-zipper motif

A

two helices zipped together to form a coiled-coil structure as dimers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

components of the promoter

A

core promoter
proximal promoter
distal promoter
enhancers

17
Q

Core promoters

A

DNA sequence -1 to -40 bases from the start of the coding DNA

  • on/off regulation of the gene
  • it’s recognized by a series of DNA-binding proteins: general transcription factors, comprising the pre-initiation complex
  • core promoter determines whether or not transcription can take place
18
Q

general transcription factors (GTF)

A
  • TBP (TATA binding protein) -recognizes the TATA sequence about 30 bases upstream from the start of the gene
  • TAFs (TBP-associated factors) a group of GTF accessory proteins necessary for the RNA Polymerase II
  • RNA polymerase II-produces the RNA
19
Q

Proximal promoter

A

-CAAT and GC boxes are bound to transcription factors such as NF1
-NF1 recruits a co-activator needed for RNA polymerase to work
-the proximal elements regulate frequency of transcription
When Cs with GC box are methylated by the cell, the gene is transcriptionally inactive

20
Q

Distal promoter

A

contains response elements (-500 to-1000 bp)

  • response elements.
  • DNA sequence that bind to proteins called specific transcriptions factors
  • the cell controls gene activity by regulation the presence or absence of the specific transcription factor
    • transcription factors are often activated by dimerization
  • every gene has its own set of response elements
21
Q

Specific transcription factors

A

may activate or repress transcription acitivty. specific to one gene (or a few genes)

22
Q

enhancers

A
  • specific DNA sequences, often found far from the target gene, which bind specific transcriptional activators (or enhancer binding proteins), and activate gene expression.
  • tens of thousands of bases away;
  • can be in any orientation
  • on enhancer, when activated, can activate a number of genes
  • enhancers are separated from each other by insulator sequences that bind to proteins that separate loops
23
Q

Glucocorticoid Receptor

A

transcription factor that controls expression of the PEPCK gene
-structure: DNA binding domain
Activation domain

24
Q

glucocorticoid Receptor 6 steps

A
  1. glucocorticoid (cortisol) is released from adrenal gland following tissue damage
  2. Cortisol passes through liver cell membrane
  3. cortisol bind to glucocorticoid receptor-receptor changes shape
  4. a newly exposed NLS allows entry into nucleus
  5. glucocorticoid receptor w/ bound hormone can bind to a glucocorticoid response element (GRE)- binds as a dimer-PEPCK gene transcription begins- newly made RNA leaves the nucleus
  6. PEPCK protein made- gluconeogenesis begins (make glucose to help in stress)
25
Q

DNA binding domain

A

Recognizes specific DNA sequence

- since it is a dimer it recognizes a palindromic sequence

26
Q

Activation domain

A

Alters transcription, usually through a copressor or coactivator

27
Q

how does glucocorticoid receptor turn on the gene?

A

Brings in coactivators that

a) supply general transcription factors for RNA polymerase II, TAFS
b) alter chromatin structure

28
Q

PEPCK

A

regulates glucose metabolism

regulated by many different hormones

29
Q

how do transcription factors affect gene transcription?

A

by altering histone-binding and making the gene accessible to RNA polymerase

30
Q

How a trancription factor works?

A

binds- to the response elements in the distal promoter
regions( recognizes the nucleotide base sequence )
recruits-proteins which help the pre-initiation complex work. called
coactivators
enhances- the RNA polymerase activity

31
Q

coactivators link transcription factors to:

A
  1. general transcription factors needed for transcription

2. chromatin re-modelling enzymes

32
Q

for the glucocorticoid receptor, the coactivator protein is called:

A

CBP coactivator, a type of histone acetyltransferase (HAT)

33
Q

CBP coactivator, a type of histone acetyltransferase (HAT)

A

acetylates the lysine (K) residues of the histones
has 2 effects:
a) reduces the strength (destabilizes) of the histone-DNA interaction
b)reduces interactions between the histone proteins

34
Q

histone acetyl transferase step 1

A

CBP reduces histone binding and TATA box is exposed

35
Q

histone acetyltransferase step 2

A

pre initiation of complex has its own histone acetyltransferase activity

  • subunit TAFII250 keeps acetylating the histones as it transcribes
  • all this is going at about 30 nucleotides per second
36
Q

transcriptional repression:

A

histone deacetylases (HDACs)
Histone methyl transferases
DNA methyl transferases

37
Q

histone deacetylases (DHACs)

A

remove acetyl groups, and DNA winds up more tightly-gene activity is silences

38
Q

histone methyltransferases

A

methyl groups added to histones causes tighter DNA binding- gene activity is silenced

39
Q

DNA methyltransferases

A

add methyl groups to DNA- always at carbon 5 of cytosine
this essentially tags regions of DNA so that they are utilized (transcribed differently-usually a sign of inactivation this is a reversible process, but DNA methylation is passed on

Cell Biology (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions