A level OCR Biology Module 6 > 6.1.1 Cellular control > Flashcards

6.1.1 Cellular control Flashcards

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1
Q

what are gene mutations?

A

a change in the sequence of bases in DNA

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2
Q

what can increase the rate of mutations?

A

mutagens

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3
Q

what are the different types of mutation?

A

-substitution
-deletion
-insertion

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4
Q

what are the different effects of mutation?

A

-no effect
-damaging
-beneficial

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5
Q

how can mutations have no effect?

A

due to degenerative nature of DNA, the phenotype can be unaffected

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6
Q

how can mutations have a damaging effect?

A

the phenotype is affected negatively, the protein no longer functions or is not synthesised

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7
Q

how can mutations have a beneficial effect?

A

this is very rare but the protein synthesised gives a useful characteristic

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8
Q

describe the genetic mutation of substitution

A

-replacement of one nucleotide with another
-changes the codon

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9
Q

what are the different forms of substitution mutations?

A

-mis-sense mutation
-silent mutation
-non-sense mutation

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10
Q

what is a mis-sense mutation?

A

when a nucleotide is substituted which could code for a new amino acid

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11
Q

what is a silent mutation?

A

when a nucleotide is substituted but the code is degenerate so the new codon may still code for the same amino acid

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12
Q

what is a non-sense mutation?

A

when a nucleotide is substituted an it results in a codon becoming a stop codon

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13
Q

what is an example of substitution genetic mutation?

A

sickle cell anaemia

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14
Q

describe the genetic mutation of insertion

A

insertion is the addition of a new pair of bases

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15
Q

describe the genetic mutation of deletion

A

deletion is the loss of a base pair (or more)

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16
Q

what can insertion and deletion mutations lead to?

A

-lead to frameshift mutation which is when the addition or removal of a nucleotide moves the reading frame of the sequence of bases
-results in changes of secondary and tertiary structure of a protein being altered

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17
Q

what is the effect of a non-sense mutation?

A

-shortened protein synthesised
-normally a negative effect

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18
Q

what is the effect of a mis-sense mutation?

A

-incorporation of incorrect amino acid in primary structure of protein
-could be silent, beneficial or harmful

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19
Q

what is a conservation mutation?

A

when a new amino acid has similar properties to its original

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20
Q

what are the different genes involved in protein synthesis?

A

-housekeeping genes
-tissue specific genes

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21
Q

what do housekeeping genes do?

A

genes that code for constantly required proteins i.e. enzymes for respiration

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22
Q

what do tissue specific genes do?

A

genes that code for proteins that are only required by certain cells at certain times i.e hormones

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23
Q

what can happen to genes during protein synthesis?

A

genes can be regulated at several points during protein synthesis

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24
Q

why are genes regulated during protein synthesis?

A

this prevents cellular resources and energy from being wasted

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25
how are genes regulated?
genes can be switched off when they are not needed
26
what are the four ways of regulating gene expression in protein synthesis?
-through transcriptional control -through post transcriptional control -through translational control -through post translational control
27
what is transcriptional control?
-the genes can be turned on or off so this will determine if the mRNA is even made
28
what are the four key areas of transcriptional control?
-chromatin remodeling -histone modification -operons -transcriptional factors
29
what are the two forms of chromatin in chromatin remodeling?
-heterochromatin -euchromatin
30
describe heterochromatin
-tightly wound (condenses) -RNA polymerase can not get to genes -during cell division
31
describe euchromatin
-DNA loosely wound around histones -not visible in cell -RNA polymerase can access genes -ensures protein synthesis only during interphase
32
what is histone modification?
it affects how tightly the chromatin is wound
33
what are the three forms of histone modification?
-methylation -acetylation -phosphorylation
34
what is methylation?
-it is when a methyl group is added -this makes histones more hydrophobic therefore they wind more tightly -this prevents transcription
35
what is acetylation?
-it is when an acetyl group is added -this causes DNA to become less negative therefore less attraction to histones which means it unwinds -this allows transcription
36
what is phosphorylation?
-this is when a phosphate group is added -this causes DNA to become less negative therefore less attraction to histones which means it unwinds -this allows transcription
37
what are operons and what do they do?
-groups of genes that are under the control of the same regulatory mechanism and are expressed at the same time -more common in prokaryotes -save energy/resources
38
what are transcriptional factors and what do they do?
-proteins which bind to DNA -repressors bind to the DNA and prevent RNA polymerase from binding, preventing transcription -some activate (turn on the genes).
39
what is post transcriptional control?
-the mRNA is modified, this will then regulate the process of translation
40
what are the two key ways that post transcriptional control is done?
-splicing -RNA processing
41
what is splicing?
when pre-mRNA is spliced (introns are removed to form functional mRNA)
42
what is the method of splicing?
-the spliceosome (enzyme) causes the intron to form a loop shape -the intron is excised and the exons are then spliced together -the mRNA may then leave the nucleus into the cytoplasm for the next stage of protein synthesis
43
what is the enzyme involved in splicing?
spliceosome
44
what is RNA processing?
-cap is added to the 5' end -tail is a long chain of adenine nucleotides that are added to the 3' end -stabilise mRNA and delay degradation in the cytoplasm -cap aids binding of mRNA to ribosomes
45
what is another part of RNA processing?
RNA editing
46
what is RNA editing?
-addition, deletion or substitution of bases -same effect as point mutations -increases the range of proteins that can be produced from a single mRNA strand/gene
47
what is translational control?
-this is where translation can be stopped or started through -degradation of the mRNA -inhibitory proteins can bind the mRNA and prevent translation -initiation factors and binding to ribosomes
48
what is post translational control?
-when proteins are modified after production which can change their functions, this is done through -addition of non protein groups -folding/shortening of proteins -the activation of proteins by cyclic AMP
49
what is cyclic AMP and what does it do?
-this is a second messenger inside cells formed from ATP -stimulated to act by Adenylyl cyclase -alters proteins tertiary structure
50
what is an example of operons?
LAC operon
51
what is a LAC operon and why is it needed/how does it work?
-E.Coli only produces the enzymes needed to metabolise lactose only when lactose is present -if lactose is not present then a 'repressor' is produced to stop lactase being produced
52
what are the parts of a Lac operon?
-regulator gene -promoter -operator -structural genes
53
what is a regulator gene?
codes for a protein called a repressor protein
54
what is a promotor
where RNA polymerase binds to catalyse the transcription of mRNA from the structural genes
55
what is an operator?
if the operator is free (the repressor protein can bind here), then the promoter is available for the RNA polymerase to bind to, so transcription of the gene occurs
56
what are the control regions of an operon?
promoter and operator
57
what are the different structural genes in a Lac operon?
B-Galactosidase and lactose permease
58
what does B-Galactosidase do?
enzyme that hydrolyses lactose
59
what does lactose permease do?
enzyme that enables the uptake of lactose
60
draw a Lac operon and label each area
*see paper flashcard*
61
draw and describe what happens at a lac operon when the genes are switched off: no lactose present
*see paper flashcard*
62
draw and describe what happens at a lac operon when the genes are switched on: lactose present
*see paper flashcard*
63
what are homeobox genes?
these are genes that control the development of the body plan of an organism
64
how are homeobox genes structured?
-it is a sequence of DNA- 180 nucleotides long coding for a polypeptide which is highly conserved -the homeobox genes are in Hox clusters
65
what do homeobox genes code for?
-the genes code for a region of the protein called the homeodomain which binds to DNA and controls the transcription of genes further along the DNA
66
how many hox clusters do vertebrates have?
vertebrates have 4 clusters
67
what do homeobox genes do?
-they determine: general body plan (polarity), number of body segments and number of placement of appendages -they are expressed in a specific order to determine embryo development
68
what does it mean when homeobox genes control polarity?
it controls what orientation the embryo will develop in
69
how do homeobox genes differ across species?
homeobox genes are the same genes across animal species, which is why embryos look similar in the early stages of development
70
how are homeobox genes expressed?
-genes in these clusters are expressed in certain body segments at certain stages of development -there is homology between homeobox genes in mice and humans
71
what does it mean that homeobox genes are highly conserved?
-as homeobox genes are conserved between species, the early stages of embryonic development look very similar -the more complex the organism, the more clusters of these genes they will have -they are fundamental, so any mutation means that the organism will not survive -each kingdom has its own set of homeobox genes
72
describe the process of apoptosis
1. enzymes (capases) break down cell cytoskeleton 2. cytoplasm becomes dense and organelles tightly pack together 3. cell surface membrane changes and small bits called Blebs form and the chromatin condenses and DNA breaks into fragments and the nuclear envelope breaks down 4. cell breaks up into vesicles or apoptic bodies, ready for phagocytosis
73
how is apoptosis controlled?
by cell signalling
74
what are the different signals for apoptosis?
-cytokinesis -hormones -growth factors -nitric oxide
75
what external factors can affect the expression of regulatory genes?
-change in temperature -change in intensity of light -stress
76
what internal factors can affect the expression of regulatory genes?
-release of hormones -psychological stress
77
why does the process of apoptosis not damage nearby cells?
because the enzymes that break everything down are in vesicles so they can't damage other cells
78
when a cell is undergoing apoptosis, it can release chemicals, what do these stimulate?
stimulates mitosis and cell proliferation, leading to the remodelling of tissues
79
what is morphogenetic apoptosis?
shaping of body parts by removing unwanted cells
80
what happens if the rate of mitosis does not equal the rate of apoptosis?
-If mitosis occurs faster than apoptosis: Too many cells are produced and not enough are removed. This leads to excess cells, causing abnormal tissue growth or tumours. -If apoptosis occurs faster than mitosis:Cells are removed faster than they are replaced. This results in too few cells, which can cause underdeveloped tissues or organs
81
what role does apoptosis play in limb development?
Apoptosis removes the cells between developing digits in the limb bud. This separates the fingers and toes and helps shape the final structure of the limb.
82
what is an example of morphogenetic apoptosis?
development of the hand
A level OCR Biology Module 6
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