Cellular Control Flashcards
1
Q
Definition of apoptosis
A
A series of biochemical events leading to an orderly and tidy cell death
2
Q
Definition of body plan
A
The basic shape of members of an animal phylum.
General structure of an individual organism.
3
Q
Definition of cAMP
A
Second messenger that activates a cascade of enzymes
4
Q
Definition of deletion
A
Removal of a base in a DNA sequence
5
Q
Definition of epigenetics
A
Study of heritable changes in gene expression
6
Q
Definition of exon
A
Any part of a gene that will encode a part of the final mature RNA
7
Q
Definition of frameshift (mutation)
A
Genetic mutation caused by insertions or deletions
8
Q
Definition of gene expression
A
Making the protein/product encoded by a gene
9
Q
Definition of gene regulation
A
Controlling which proteins/products are made by each cell
10
Q
Definition of homeobox genes
A
One group of gene with a common DNA sequence that code for the homeodomain.
Genes responsible for the development of body plans
11
Q
Definition of Hox genes
A
Example of a homeobox gene.
Any developmental control genes used in the identification of each body segment
12
Q
Definition of insertion
A
Addition of a base in a DNA sequence
13
Q
Definition of intron
A
Non coding sequence of DNA within a gene that is removed during the maturation of RNA
14
Q
Definition of lac operon
A
Region of DNA in E. Coli that controls the production of proteins involved in the breakdown of lactose
15
Q
Definition of missense (mutation)
A
A point mutation resulting in a codon that codes for a different amino acid
16
Q
Definition of mutagen
A
Agent of a substance that can bring about a permanent alteration to the physical composition of a DNA gene.
17
Q
Definition of mutation
A
A random change in the DNA base sequence that changes the message carried by that gene
18
Q
Definition of nonsense (mutation)
A
A point mutation in a sequence of DNA that results in a premature stop codon
19
Q
Definition of operator
A
A region of DNA the repressor binds to
20
Q
Definition of operon
A
A set of genes transcribed under the control of an operator gene
21
Q
Definition of point (mutation)
A
A change of one nucleotide base in the DNA/RNA molecule
22
Q
Definition of promoter
A
Region of DNA that the RNA polymerase binds to
23
Q
Definition of regulatory gene
A
A gene that codes for a repressor protein
24
Q
Definition of repressor protein
A
Binds to the operator in order to block RNA polymerase
25
Definition of silent (mutation)
Mutated codon still codes for same amino acid due to degenerate nature of genetic code.
OR
Occurs in non-coding region of DNA so no subsequent change in the amino acid/function of the overall protein
26
Definition of splicing
The process where introns are removed
27
Definition of structural genes
Genes that control the production of a protein that performs a structural role in the cell
28
Definition of substitution
When one or more base is exchanged for the same number of bases
29
Definition of syndactyly
A condition in which fingers or toes are joined together
30
Definition of transcription factors
A protein that controls the rate of transcription of genetic information from DNA to mRNA by binding to a specific DNA sequence.
31
What do genes control?
How cells/organisms grow, develop and function
32
What do genes produce?
Proteins that control the structure/function of a cell
33
What cells can mutations occur in?
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Body cells (somatic)
Reproductive cells (germ-line)
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34
When do mutations occur?
Spontaneously during DNA replication at a rate of 1 in 50,000,000 base pairs
35
What speeds up the rate of mutations?
Mutagens eg carcinogenic chemicals in tobacco smoke
36
What are the 3 things mutations can be?
Harmful eg cancer/genetic diseases
Neutral (no effect)
Beneficial (rare but often lead to evolution)
37
What are the 4 types of mutations?
Point
Substitution
Insertion
Deletion
38
What are the 4 effects a mutation can have?
Silent
Missense
Nonsense
Frameshift
39
What is the effect of a missense mutation?
The mutated codon now codes for a different amino acid. If the amino acid is chemically similar, the protein may function normally. If the amino acid is chemically different, there may be a loss of shape and therefore function.
40
What is the effect of a nonsense mutation?
The mutated codon now codes for a stop codon so protein synthesis is terminated earlier. The protein produced is therefore truncated and may not function normally.
41
What is the effect of a frameshift mutation?
If one or more base is inserted/deleted the reading frame of the ribosomes is shifted so every subsequent codon is incorrect. This will likely lead to many incorrect amino acids and therefore loss of function.
42
What are the 2 transcription factors in eukaryotes?
Activators or repressors
43
What is the transcription factor in prokaryotes?
Normally just repressors
44
Definition of RNA polymerase?
Transcribes a gene
45
Definition of Lac Z, Y and A?
Structural genes that code for enzymes involved in lactose utilisation.
Beta galactosidase - breaks down lactose
Lactose permeare - allow lactose into cell (create protein channels in membrane)
46
What percentage of human genes code for proteins that switch other genes on and off?
10%
47
What are transcription factors?
Proteins/short pieces of non-coding RNA
| Bind to specific regions of DNA to increase/decrease the rate of transcription and therefore protein production
48
Where are transcription factors made?
Coded for by regulatory genes often located some distance away from the gene they regulate
49
When lactose is present what happens at the lac operon?
The lactose binds to the repressor, removing it from the operator. This means RNA polymerase can bind to the promoter to make Lac Z, Y and A produce the enzymes to break down lactose.
50
When lactose isn't present, what happens at the lac operon?
There is no lactose so the repressor binds to the operator. This prevents RNA polymerase from binding to the promoter so Lac Z, Y and A don't produce the enzymes to break down lactose
51
What are the 4 categories of controlling gene expression?
Transcriptional
Post transcriptional
Translational
Post translational
52
What is the mechanism for controlling gene expression at the transcriptional level?
The process of transcription is prevented so mRNA is not synthesised
53
What is the mechanism for controlling gene expression at the post transcriptional level?
The mRNA is modified to change the protein produced in translation
54
What is the mechanism for controlling gene expression at the translational level?
Translation is prevented
55
What is the mechanism for controlling gene expression at the post translational level?
The polypeptide is modified after synthesis to activate it or change its structure
56
What is the general transcription factor?
Basal
57
What do Basal transcription factors do?
Help RNA polymerase attach to the promoter.
| RNA polymerase and the basal transcription factors form a transcription pre-initiation complex
58
What do activator transcription factors do?
Bind to enhancer region of DNA
Help form transcription pre-initiation complex
Starts or speeds up transcription
59
What do repressor transcription factors do?
Binds to silencer region of DNA (Often a long way away from gene)
Prevents formation of the transcription pre-initiation complex and therefore, slow down/stop transcription
60
What is combinatorial regulation?
When a gene is controlled by several different transcription factors.
A specific combination is needed to turn a gene on.
61
What happens at the post transcriptional level of controlling gene expression?
Alternative splicing
| Different introns can be spliced out of the primary mRNA to make different mature mRNA
62
What is RNA editing?
The alteration of the sequence of nucleotides in the RNA after it has been transcribed from DNA but before it is translated into protein.
63
What is protein kinase A?
A family of enzymes which are activated/deactivated by cAMP. PKA phosphorylates a number of different proteins to activate them. Different cell types have different proteins available for phosphorylation so effects of PKA change depending on cell type.
64
How does cAMP activate PKA?
PKA has 4 subunits and when cAMP binds it changes the enzymes 3D shape, releasing the active subunits - PKA is now active.
65
What happens at the post translational level of controlling gene expression?
Protein activation
| The activation of intracellular proteins in response to an external signal.
66
What are the 3 parts of body plans?
Symmetry, segmentation and limb positioning
67
What is the difference between internal and external segmentation?
Internal is about the different layers of tissues (gut, muscle, skin etc)
External is head, thorax and abdomen
68
What are the 3 types of symmetry?
Bilateral - In half (humans)
Radial symmetry - lots of symmetry
No symmetry
69
What does the order of the Hox genes on the DNA correspond to?
The order of the segments of the body which are activated by each Hox gene. This is called co-lineasity
70
How many clusters of Hox genes do humans have?
4
71
How do Hox genes work?
They encode for transcription factors that switch on whole clusters of genes at once.
Eg all genes encoding proteins to make human limbs are switched at week 6 of pregnancy.
72
What does the homeodomain bind to?
A specific sequence of DNA in the promoter of the target genes
73
What does the transcription activation domain do?
Increase or decrease rate of transcription
74
Why are fruit flies ideal for studying mutations?
They only have 1 set of Hox genes so if there is a mutation in the DNA something should be observed.
75
Why is the homeobox sequence similar in plants, animals and fungi?
DNA binding sites near the target genes are the same across all organisms
The homeobox sequence codes for the homeodomain region.
The transcription factor binds to the DNA by the homeodomain region
76
Why is the homeobox sequence highly conserved?
If a mutation occurred in a germline cell, it would change the shape of the homeodomain region. This may make it unable to bind to DNA. Whole clusters of developmental genes won't be turned on. Would have serious effects on the body plan. Mutation could be lethal. Any organism with the mutation would likely be selected against. So the mutation wouldn't be passed on.
77
What does selected against mean?
Wouldn't reach reproductive age
78
What 2 processes work together to control growth/repair?
Apoptosis and mitosis
79
What is necrosis?
Untidy cell death where the inside of the cell then leaks out
80
What happens at the start of apoptosis?
The cell begins to bleb and the nucleus starts to disintegrate. The cytoskeleton is broken down by enzymes.
81
What happens after the cytoskeleton is broken down in apoptosis?
Cell fragments are produced with intact plasma membranes and containing organelles.
82
What happens after the fragments are made in apoptosis?
Cell fragments are ingested and digested by phagocytic cells
83
What regulates mitosis/apoptosis?
Hox genes
84
What regulates the expression of Hox genes?
Stimuli and stress
85
What are the 2 types of stress that regulate the expression of Hox genes?
Internal - Damage to DNA/ release of hormones/ psychological stress
External - Change in light intensity / temperature / pathogen attack / lack of nutrients / drugs
