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Cellular Control - M6 Flashcards

1
Q

Point / substitution Mutation

A

One base is replaced with another.

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2
Q

Addition / insertion / frameshift
Mutation

A

An extra base is added to the DNA molecule.

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3
Q

Deletion / frameshift

A

A base is removed from the DNA molecule.

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4
Q

Mutation causes no effect

A

no effect on phenotype of organism because normally functioning proteins are still synthesized

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5
Q

Damaging effects of mutations

A

phenotype of organisms is affected in a negative way because proteins are no longer synthesized or proteins synthesized are non-functional. Can interfere with one or more essential processes

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6
Q

Beneficial mutations

A

very rarely a protein synthesised that results in a new and useful characteristic in phenotype.

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7
Q

Genes can be regulated in 4 different ways:

A

Transcriptional – genes can be turned on or off

Post-transcriptional – mRNA can be modified which regulates translation

Translational: turning translation on/off

Post-translational – proteins can be modified after synthesis

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8
Q

Chromatin remodelling

A

Histones + DNA = chromatin

Heterochromatin is tightly wound DNA – visible during cell division
RNA polymerase can’t access gene so transcription can’t occur

Euchromatin – loosely wound DNA – present during interphase – this is when transcription can take place as RNA polymerase can bind

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9
Q

Histone modification

A

Histones are +ve and DNA is -ve

Histones can be modified to increase or decrease the level of packing

Acetylation or phosphorylation reduces +ve charge on histones causing it to coil less tightly allowing transcription

Methylation makes histones more hydrophobic so they bind closer together

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10
Q

RNA editing

A

Bases can be added, deleted or substituted
This increases the range of proteins that can be produced from a single gene

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11
Q

Translational control

A

Degradation of mRNA - The more resistant the molecule, the longer it will last in the cytoplasm, so more protein can be synthesised

Inhibitory proteins – bind to mRNA to stop it from binding to a ribosome

Activation of initiation factors which aid the binding of mRNA to ribosomes

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12
Q

Protein kinases

A

Catalyse addition of phosphate groups to proteins to change the tertiary structure and function

This usually activates enzymes so regulate cell activity

cAMP activates lots of protein kinases

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13
Q

Modification of proteins

A

Addition of non-protein groups

Modifying amino acids and the formation of bonds
Folding/shortening of proteins

Modification by cAMP – e.g. the lac operon cAMP binds to the cAMP receptor proteins increasing the rate of transcription of the structural genes

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14
Q

Control sites:

A

do NOT code for polypeptides

Promoter Region (P) DNA sequence where RNA polymerase binds

Operator Region (O) where repressor protein binds to

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15
Q

Structural genes

e.g:

A

:code for proteins not involved in gene regulation
Structural Gene (Z)
Structural Gene (Y)
Structural Gene (A)

Make
B- galactosidase
Lactose permease
Lactose transacetylase

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16
Q

Operon

A

A group of genes controlled by the same regulatory mechanism at the same time

An operon is a length of DNA made up of structural genes and control sites
The control sites regulate the expression of the structural genes

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17
Q

β-galactosidase in Gene regulation in Escherichia coli

A

hydrolyses lactose to glucose and galactose

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18
Q

Lactose permease in Gene regulation in Escherichia coli

A

enables the bacterium to take up lactose

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19
Q

β-galactosidase, Lactose permease enzymes are only produced in presence of …

A

These enzymes are only produced by the bacterium in the presence of lactose, indicating that there is a regulatory mechanism at work – the lac operon!

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20
Q

Describe how Genes Z and Y are switched on in bacteria that are moved to a nutrient medium which contains Lactose

A

lactose binds to repressor protein ;
changes , shape / structure (of protein) ;
removes it from / stops it binding to , operator ;
RNA polymerase binds to promoter ;
idea that (so that Z and Y) are , transcribed / mRNA made

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21
Q

Transcriptional control involves

A

Chromatin remodelling

Histone modification

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22
Q

Post-transcriptional/pre-translational control involves

A

RNA processing

RNA editing

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23
Q

Translational control involves

A

Degradation of mRNA

Inhibitory proteins

Activation of initiation factors which aid the binding of mRNA to ribosomes

Protein kinases

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24
Q

Post- translational control involves

A

Modifications of proteins

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25
A homeobox is a DNA sequence that codes for a
protein transcription factor homeodomain
26
This means they help to form the basic pattern of the body For example, they control the............ of the organism (which end will develop into the head and which end will develop into the tail) They also control the............ of organisms such as insects and mammals into distinct body parts and they control the development of body parts such as wings and limbs, as well as what ............. are present in each section of the body
polarity segmentation organs
27
!! DIFFERENCE BETWEEN Homeobox and homeobox gene
homeobox = DNA sequence that codes for a protein transcription factor- homeodomain WHEREAS a homeobox gene is any gene that contains a homeobox sequence
28
Why are homeobox genes similar between animals, fungi and plants
they all code for amino acid sequences that will form transcription factors, the DNA binding regions of which must have the same shape
29
why are homeobox gene sequences highly conserved
-genes very important -mutation would have big efects - alter body plan -Many other genes effected -Mutations that cause variation in homeobox sequences can lead to organisms that are not viable (not properly developed) so are not favored by natural selection. Strong negative selection pressure
30
Homeobox genes summary​
Regulatory genes **code for homeodomain (part of a protein)** Control body development Regulate mitosis and apoptosis 180 bp Homeobox genes are genes whose activity switches a whole set of other genes on or off, affecting an organism’s body plan (overall design of an organism’s body).​ They are found in clusters called hox clusters​ Most animals have very similar homeobox genes.​ Genes are highly conserved (have not evolved much)​ Code for production of transcription factors. These can bind to certain sections of DNA and cause it to be transcribed.​
31
Hox genes
a very important subset of homeobox genes One group of Homeobox genes only present in animals​ determine the identity of embryonic body regions along the anterior-posterior axis (i.e. the head-tail axis) ​ They are responsible for correct positioning of body parts.​ ​ In animals, they are found in gene clusters, mammals have 4 on different chromosomes.​ ​ The order in which they appear along the chromosome is the order in which their affects are expressed in the organisms.​ ​ Humans have 39 Hox genes.
32
Diploblastic animals have
Diploblastic animals have two primary tissue layers (jellyfish, corals, anemones)​
33
Triploblastic animals have
Triploblastic animals have three primary tissue layers (arthropods and vertebrates)​
34
Hox genes in the head control
Hox genes in the head control the development of mouthparts,
35
Hox genes in the thorax control
Hox genes in the thorax control the development of wings, limbs or ribs.
36
​ Individual vertebrae and structures develop from segments in the embryo called _______. They are directed by ____ ______ to develop in a particular way depending on their _______.
​ somites. Hox genes. position.
37
A homeobox is a DNA sequence that codes for a protein transcription factor The transcription factors (that homeobox sequences code for) attach to DNA at specific locations and regulate the transcription of genes (e.g. genes that control the early development of eukaryotic organisms) by turning various different genes on and off in the correct order
A homeobox is a DNA sequence that codes for a protein transcription factor The transcription factors (that homeobox sequences code for) attach to DNA at specific locations and regulate the transcription of genes (e.g. genes that control the early development of eukaryotic organisms) by turning various different genes on and off in the correct order
38
Radial body shape
Radial – no left or right, only top and bottom. Jellyfish are an example​
39
Bilateral body shape
Bilateral – left and right, head and tail. Most animals are an example.​
40
Asymmetry body shape
Asymmetry – no lines of symmetry. Sponges are an example.​
41
How do Homeobox genes work
The proteins produced act as transcription factors​ - molecular switches which mRNA production ON or OFF​ - they do this by binding to specific DNA sequences called regulatory elements​
42
All homeotic genes share the same ___ base sequence encoding_____ ______sequence of amino acids​
180 The same
43
HOMEOBOX sequence​ binds
This section of the protein binds to the groove in the DNA double helix
44
What is apoptosis
Programmed cell death
45
Cyclins act as .......... CDKs act as ........ (once activated by cyclins)
regulators catalysts
46
Process of apoptosis
-The DNA of the cell becoming denser and more tightly packed -The nuclear envelope of the cell's nucleus breaking down and chromatin condensing -Vesicles forming that contain hydrolytic enzymes -Phagocytes engulfing and digesting the cell via phagocytosis
47
Mitosis and apoptosis
Both are essential in shaping organisms​ Mitosis increases the number of cells available for growth.​ Apoptosis helps to shape body parts by removing cells and tissues.​ Cells undergoing apoptosis can release chemical signals which stimulate mitosis and cell proliferation, leading to remodelling of tissues.​ Hox genes regulate both mitosis and apoptosis.
48
Example of External stimulus of genes regulating cell cycle
External e.g: stress caused by lack of nutrient availability, could result in gene expression which prevents cells from undergoing mitosis
49
Example of External stimulus of genes regulating apoptosis
gene expression which leads to apoptosis being triggered can be caused by attack by a pathogen
50
Example of internal stimulus of genes regulating apoptosis and cell cycle
DNA damage. if DNA damage is detected during cell cycle, can result in expression of genes which cause cell cycle to pause and then even apoptosis
51
Mitosis is controlled by various different genes that are categorised into two distinct groups: ........-.........are genes that stimulate cell division ........-.......... genes are genes that reduce cell division
Proto-oncogenes Tumour-suppressor
52
Tumour-suppressor genes can also............. ............... in cells with damaged DNA that cannot be repaired
stimulate apoptosis
53
Clusters of homeobox genes are called
hox clusters.
54
Larger organisms have ______ hox clusters
more
55
The regulation of the pattern of anatomical development is called ________
morphogenesis.​
56
DNA is _____ charged due to ______ _______ groups. While histones are ________ charged This way they can bind together
Negatively Negative phosphate Positively
57
Regulatory genes
Proteins involved in DNA regulation E.g repressor protein (lac I)
58
Epigenetics is
term used to describe the control of gene expression by the modification of DNA. sometimes used to include all of the different ways in which gene expression is regulated
59
why is the genetic code degenerate
, because a single amino acid may be coded for by more than one codon. Meaning a point mutation may have no effect, allowing the same protein to be made for normal functioning
60
what is a point mutation
If only one amino acid is affected by substitution, insertion or deletion
61
Frameshift mutation
e.g: insertion and deletion Disrupts triplet code reading
62
Codon
A sequence of three bases which codes for a particular amino acid
63
Mutations can occur _____, often during ______ ____________, but the rate of mutations is increased by ________
spontaneously DNA replication mutagens
64
Physical mutagens e.g how
ionizing radiation such as X-rays break one or both DNA strands. Some breaks can be repaired, but mutations can occur in the process
65
Chemical mutagens e.g: How
Deaminating agents chemically alter bases in DNA such as converting cytosine to uracil in DNA, changing the base sequence
66
3 types of biological mutagens
alkylating agents base analogs viruses
67
alkylating agents in mutation
methyl or ethyl are attached to bases resulting in the incorrect pairing of bases during replication
68
base analogs in mutation
incorporated into DNA in place of the usual base during replication, change base sequence
69
Viruses in mutation
viral DNA may insert itself into a genome, changing the base sequence
70
reasons for a silent mutation
-mutation occur in non-coding region of DNA (introns) -code for same amino acid due to degenerate nature of the genetic code -may result in changes to the primary structure that do or effect the overall structure or function of proteins synthesised
71
Nonsense mutations
result in a codon becoming a stop codon. Result in a shortened protein being synthesised which is normally non-functional. Normally have negative effects on phenotypes
72
Missense mutations
result in incorporation of an incorrect amino acid(s) into the primary structure when the protein is synthesised. Result depends on the role the amino acid plays in the structure and .: function of the protein synthesised
73
Chromosome mutations
effect the whole chromosome or number of chromosomes within a cell Can be caused by mutagens or normally in meiosis
74
changes in chromosome structure during chromosome mutations =
-Deletion -Duplication -Translocation -Inversion
75
Deletion in chromosome mutations
section of chromosome breaks off and is lost within cell
76
translocation chromosome mutations
section of one chromosome breaks off and joins another non-homologous chromosome
77
Inversion chromosome mutations
section of chromosome breaks off, is reversed and then joins back onto chromosome
78
modifying mRNA - 4 steps
1) RNA splicing. remove introns 2)Add cap (modified nucleotide) to 5' 3)Add tail of adenine to stabalise mRNA, prevent degredation 4)mRNA editing . make different versions of mRNA to make different proteins
79
Two ways to decrease Translation
A) Degrade mRNA B)Inhibitory proteins bind to mRNA so that it can't bind to a ribosome
80
How to increase Translation
Activate initiation factors -allowing mRNA to bind to Ribosome -by phosphorylation of proteins to activate them which is done by Protein kinases -Protein kinases can be activated by cAMP
81
Post-translational gene control 4 ways
A) add non-protein groups B)Modify amino acids to make bonds C)Protein folding (tertiary and quaternary) D) Modification by cAMP (activation)
82
2 example of Post-translational gene control Modification by cAMP (activation)
1) cAMP + CRP binds to RNA polymerase to upregulate its activity 2) cAMP activates kinases Kinases then go onto phosphorylate and activate other enzymes and proteins
83
Lac operon In presence of glucose or Lactose process
1) when glucose is present, lac I is expressed to make repressor protein. Binds to operator, blocks Promoter (RNA binding site) 2) RNA polymerase can't bind to Promoter due to blockage, no transcription of 3 structural genes 3)when Lactose is present, it binds to repressor protein, causing a conformational gene. Hence the repressor can no longer bind to the operator, unblocking the Promoter 4)RNA polymerase then binds to the Promoter to start transcription 5)CRP can bind to cAMP and the whole complex can bind to RNA polymerase to upregulate its activity 6) Glucose decreases cAMP concentration inside cell. Hence the CRP-CAMP-RNA polymerase complex will dissociate, down regulating transcription 7)Lactose is released from the repressor protein. The repressor protein binds to the operator once more, preventing RNA polymerase from binding to the promotor to start transcription again
84
does lack O (operator gene) code for a protein
no
85
is cyclic AMP made of protein
nein remember, made from ATP
86
what stage of meiosis does independant assortment accour
Metaphase I and Metaphase II
87
what stage of meiosis does independant assortment accour
Metaphase I and Metaphase II
88
outline roles of PCR in sequencing a genome
amplify DNA different lengths of fragments/ chain termination
89
outline roles of electrophoresis in sequencing a genome
tp put DNA in size order to read base sequence
90
outline roles of digestion of DNA by restriction enzymes in sequencing a genome
to cut (genome DNA) into smaller (750 bp) fragments to cut vectors / BACs / plasmids (for gene library)
91
why genome has to be fragmented before sequencing
-genome too big/ very large -accuracy better/fewer errors -divide job ober time/ different labs
92
where does repressor protein bind
operator region

Biology (45 decks)

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