Chapter 18 Flashcards
(101 cards)
1
Q
What regulates development in multicellular euk?
A
gene expression
2
Q
What regulates development in bacteria?
A
They regulate transcription to respond to environmental changes.
3
Q
What type of bacteria is favored by natural selection?
A
The kind that produces only what is needed by the cell.
4
Q
How can a cell regulate the production of enzymes?
A
feedback inhibition
or
gene regulation
5
Q
operon model
A
a cluster of functionally related genes can be coordinately controlled by a single “switch”
6
Q
operon
A
the entire stretch of DNA that includes the operator, the promoter, and the genes that they control
7
Q
Trp operon
A
5 genes clustered together with a single promoter
8
Q
operator
A
the “on-off switch” -> a segment of DNA usually in the promoter
9
Q
repressor
A
can switch the operon off
10
Q
regulatory gene
A
produces the repressor / produced by separate gene from the DNA it is regulating
11
Q
By itself, is trp repressor active or inactive?
A
inactive
12
Q
corepressor
A
a molecule that cooperates with a repressor
13
Q
How does the repressor prevent gene transcription?
A
binds to the operator and blocks RNA polymerase
14
Q
repressible operon
A
(like Trp operon) an operon that is usually on
15
Q
inducible operon
A
(like the lac operon) an operon that is usually off -> needs inducer to inactivate repressor and turn on transcription
16
Q
inducer
A
inactivated repressor and turns on transcription
17
Q
When are hydrolyzing enzymes needed?
A
When lactose is present
18
Q
What does the lac operon do?
A
It codes for enzymes used in hydrolysis and metabolism of lactose
19
Q
negative control
A
operons are switched off by the active form of the repressor
20
Q
positive control
A
stimulatory protein activator of transcription
21
Q
CAP
A
catabolite activator protein
22
Q
What can activate CAP? (When glucose is short.)
A
cyclic AMP (cAMP)
23
Q
How does the activated CAP accelerate transcription?
A
through attaching to the promoter and increasing the affinity of RNA polymerase
24
Q
At what stages is gene expression regulated?
A
- Transcription (chromatin, transcription factors)
- mRNA processing (splicing, tail,cap)
- mRNA transport
- mRNA stability/degradation
- Initiation of Translation
- Control of protein activity (posttranslational modifications)
- protein degradation
25
What do chemical modifications do to histones and DNA of chromatin?
influence chromatin structure and gene expression
26
The addition of _____ can condense chromatin.
methyl groups
27
histone acetylation
acetyl groups are attached to positively charged lysines in histone tails
loosens chromatin structure to promote transcription
28
DNA methylation
the addition of methyl groups to certain bases in DNA (usually cytosine)
reduces transcription in some species (prevent (or enhance) some binding of transcription factors, long-term inactivation, regulates one of the parents in genomic imprinting)
29
Do these changes change DNA?
No
30
Can these modifications be passed to the next generation?
Yes
31
epigenetic inheritance
the inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
32
Epigenetic inheritance in twins
more epigenetic tags as they get older
33
How do chromatin-modifying enzymes provide initial control of gene expression?
by making a region of DNA either more or less able to bind the transcription machinery
34
What is involved in regulation of transcription initiation?
proteins that bind to DNA
35
control elements
segments of noncoding DNA that serve as binding sites for transcription factors (critical to precise regulation of gene expression)
36
Where are proximal control elements located?
close to the promoter
37
enhancers (distal control elements)
may be far away from a gene or located in an intron
38
general transcription factors
can bind to the TATA box or other transcription factors and RNA polymerase II
essential for coding of all protein-coding genes
39
specific transcription factors
some control elements must interact with in euk for high levels of transcription
40
activator (specific transcription factor)
a protein that binds to an enhancer and stimulated transcription of a gene
41
What are an activators 2 domains?
one that binds to DNA and the other activates transcription
42
What do bound activators do?
They facilitate a sequence of protein-protein interactions that result in transcription of a given gene.
43
Can some transcription factors act as repressors?
Yes, they inhibit expression of a particular gene by a variety of methods
44
When can a particular combination of control elements activate transcription?
Only when the appropriate activator proteins are present
liver and lens can make albumin and crystallin but only lens makes crytallin and only liver makes albumin
45
alternative RNA splicing
different mRNA molecules are produced from the same primary transcript (depending on introns and exons)
46
How can the initiation of translation of selected mRNA be blocked by regulatory proteins?
The proteins bind to sequences or structures of the mRNA and prevent the attachment of ribosomes
47
Where do the nucleotide sequences that influence the lifespan of mRNA in euk reside?
The untranslated region (UTR) at the 3' end of the molecule
48
What regulated the length of time each protein functions?
selective degredation
49
ubiquitin
how cells mark proteins for degredation
50
proteasomes
recognize ubiquitin and degrade the protein
51
How much of DNA is transcribed into noncoding RNAs?
most of it
52
2 points where noncoding RNAs regulate gene expression
mRNA translation
| chromatin configuration
53
MicroRNAs (miRNAs)
small single-stranded RNA molecules that can bind to mRNA
54
What do miRNAs do?
They can degrade mRNA or block its translation
55
How can a single miRNA potentially regulate the expression of many different genes?
imperfect base pairing
56
differential gene expression
the expression of different genes by cells with the same genome
57
When does a fertilized egg give rise to many different types of cells?
During embryonic development
58
3 factors in transformation from zygote to adult
cell division
cell differentiation
morphogenesis
59
What if only cell division happened?
Identical cells
60
cell differentiation
the process by which cells become specialized in structure and function
61
morphogenesis
the physical processes that give an organism its shape
62
What 2 major sources of developmental information "tell" a cell which genes to express?
The egg's cytoplasm (cytoplasmic determinants)
and
the environment around a particular cell [esp from nearby embryonic cells] (inductive signals)
63
What is contained in an egg's cytoplasm?
RNA, proteins, and other unevenly distributed substances
64
cytoplasmic determinants
maternal substances in the egg that influence early development
65
How does the egg lead to different gene expression?
As the zygote divides by MITOSIS, cells contain different cytoplasmic determinants
66
induction
signal molecules from embryonic cells cause transcriptional changes in nearby target cells
67
determination
commits a cell to its final fate
| precedes differentiation
68
Differentiated cells are specialists at ...
making tissue-specific proteins
| - specific structure and function
69
MyoD
(not active in the embryonic precursor cell) one of several "master regulatory genes" that produce proteins that commit the cell to becoming skeletal muscle
70
master regulatory genes
commit the cell to becoming skeletal muscle
71
muscle cells develop from ...
... embryonic precursor cells that have a potential to develop into number of cells
72
What leads to the activation of a master regulatory gene?
signals from other cells
73
myoblast
when a cell is irreversibly committed (to being a skeletal muscle cell?)
74
body plan
overall arrangement
75
When is the body plan established?
during differentiation
76
pattern formation
development of a spatial organization of tissues and organs (cytoplasmic determinants and inductive signals both contribute)
77
When does pattern formation begin in animals?
With the establishment of the major axes
78
Positional information
the molecular cues that control pattern formation, tells a cell its location relative to the body axes and to neighboring cells
79
homeotic genes
control pattern formation in late embryo, larva, and adult stages
80
embryonic lethals
mutated genes that kill the embryo
81
number of genes necessary for normal segmentation in a fly
120
82
maternal effect genes
encode cytoplasmic determinants
create mutant offspring regardless of genotype
supplied by nurse cells
83
egg-polarity genes
another name for maternal effect genes
84
bicoid gene
a maternal effect gene that affects the fly's front half
| (no bicoid = two posteriors) [morphogen]
85
morphogen
morphogens establish an embryo's axes and other features of its form
86
3 reasons bicoid research was groundbreaking
identified a specific protein required for some early steps in pattern formation
increased understanding of the mother's role in embryo development
demonstrated a key developmental concept that a gradient of molecules can determine polarity and position in the embryo
87
Mutations to what can cause cancer?
genes that regulate cell growth and division, including growth factors, their receptors and intracellular molecules of signaling pathways
88
What can cause cancer mutations?
Spontaneous or environment (Radiation, chemicals, and some viruses)
89
Oncogenes
cancer-causing genes in some types of viruses
[close counterparts in humans and animals]
90
Proto- oncogenes
the corresponding normal cellular genes responsible for normal growth and division
91
Proto-oncogenes can be converted to oncogenes by
Movement of DNA within the genome (near active promote = increased transcription)
amplification of a proto-oncogene (increase # copies)
point mutations in the proto-oncogene or its control elements (increase gene expression)
92
tumor-suppresor genes
normally help prevent uncontrolled cell growth
93
What happens if the protein production of tumor-suppressor genes is decreased?
Cancer may onset
94
What do tumor-suppressor genes do?
Repair damaged DNA
control cell adhesion
act in cell-signaling pathways that inhibit the cell cycle
95
ras gene (proto-onco)
mutations in ras can lead to hyperactivity and increased division
G protein - relay from growth factor to protein kinases -> stimulate cell cycle
mutation triggered without growth factor
96
p53
prevents a cell from passing on mutations due to DNA damage
synthesizes protein to stop cell-cycle
mutation = no stop
97
Can only one mutation lead to cancer?
Typically need mutliple
98
DNA level of cancer characteristics
at least one active oncogene and the mutation of several tumor-suppressor genes
99
Can a person inherit cancer genes?
Yes; they can inherit oncogenes or mutant alleles of tumor-suppressor genes
100
Mutated gene in colorectal cancer?
adenomatous polyposis coli (tumor-suppressor)
101
Mutated gene in breast cancer?
BRCA1 and 2
