biology > cellular control 6.1.1 > Flashcards

cellular control 6.1.1 Flashcards

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1
Q

what is a mutation ?

A

change in the sequence of bases in DNA

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2
Q

what are the types of mutation ?

A

substitution ( point ) - one nucleotide is substituted for another
deletion - a nucleotide is removed
insertion - an extra nucleotide is added

idel mutations ( deletion and insertion )

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3
Q

how do mutations have knock on effects ?

A

change in dna sequence
change in amino acid sequence
change in protein structure
change in protein function

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4
Q

what are the types of substitution mutations ?

A

silent mutation - different codon but same amino acid is made
missense mutation - different amino acid made eg. sickle cell anaemia
nonsense mutation - stop codon made which halts the formation of amino acid chain

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5
Q

what is the frame shift ?

A

when a mutation causes a change in every triplet downstream including start and stop codons
alters the proteins structure ( primary, secondary ect )
protein is no longer able to perform its function

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6
Q

what are types of phenotypic effects of mutations ( physical ) ?

A

neutral - normal functioning proteins still made ( silent mutations )
harmful - protein not made or not functional / negative phenotypic change
beneficial - protein made with new and useful characteristics

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7
Q

what increases the chance of mutations?

A

mutagens
physical - breaks strands of DNA from x rays or UV
chemical - changes one base to another from deaminating agents
biological - DNA might be inserted into the genome to change the sequence

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8
Q

what are examples of chromosome mutation ?

A

deletion - section breaks off
duplication - copied
translocation - section breaks off, regions another non homologous chromosome
inversion - section breaks off is revered and then joins back on

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9
Q

what is mRNA?

A

made in the nucleus
small enough to pass through pores
carries a copy of genetic code for a protein to ribosomes in cytoplasm
bases AGCU

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10
Q

what is tRNA ?

A

single stranded folded into pin shape held by hydrogen bonds
has the anticodon ( 3 complementary bases ) to the codon on mRNA

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11
Q

which two DNA bases are purines ?

A

adenine and guanine

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12
Q

what term descibes the position of gene on a chromosome?

A

locus

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13
Q

what are the three terms in the rules of genetic code ?

A

universal- same across all organisms
degenerate - most amino acids are coded for by more than 1 codon
non overlapping - each base is only read once

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14
Q

what are structural genes ?

A

code for a protein that has a function within a cell and is not involved in DNA regulation
eg. enzymes, hormones

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15
Q

what is a regulatory gene ?

A

code for protein that control the expression of other genes
eg. transcription factors

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16
Q

what are housekeeping genes ?

A

code for proteins that are constantly activated
eg, enzymes for respiration

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17
Q

what are tissue specific genes?

A

code for proteins that are only required at certain times to carry out a short response
eg. hormones such as those required doe growth and repair

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18
Q

what are the different levels of gene regulation ?

A

transcriptional - genes turned on or off
post transcriptional - mRNA modified to regulate the protein made
post translational - proteins can be modified after synthesis which changes their functions

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19
Q

what are the ways of transcriptional control in eukaryotes?

A
  1. chromatin remodelling
  2. transcription factors
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20
Q

what is chromatin remodelling ?

A

caused my histone modification
the DNA is positive charge and the histones are negatively this means they wrap around each other
how tightly they are wrapped can be adjusted by increases or decreasing the attraction to DNA
when they are tightly wrapped RNA polymerase cannot access the genes

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21
Q

what is heterochromatin ?

A

dna is tightly wound around histones
visible under microscope

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22
Q

what is euchromatin ?

A

dna is loosely wound around histones
non visible under microscope

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23
Q

why is chromatin remodelling useful ?

A

simple form of regulation that ensures proteins necessary for division are synthesised in time
prevents protein synthesis during division

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24
Q

what are transcription factors ?

A

proteins which move from the cytoplasm into the nucleus and bind to DNA to determine which genes are expressed
- they do this by either aiding or inhibiting the attachment of RNA polymerase to the DNA

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25
which part of the gene do transcription factors bind to ?
promoter region
26
what do activators do ?
bind to the RNA polymerase which binds to the promoter region they increases transcription and so more protein is made and the gene is expressed
27
what do repressors do ?
bind to the promoter region to prevent RNA polymerase from binding this leads to less transcription and the gene is repressed
28
give an example of a transcription factor which is made in inactive form ?
oestrogen - requires a hormone or growth factor to active it
29
what sugar does E.coli use as a respiratory substrate ?
glucose , but if this is not supplies they use lactose this is not good as it must be gained and then broken down by enzymes which requires energy
30
what is an operon ?
groups of genes that are under control of a single regulatory mechanism ( all off or all on at the same time )
31
what must the E.coli bacteria use in order to use lactose ?
the lac operon encodes enzymes for lactose uptake and metabolism ( break down )
32
what are the structural genes in the lac operon?
lac Z - beta galactosidase - hydrolyses lactose into glucose and galactose lac Y - lactose permease - facilitates lactose crossing the cell surface membrane into the cell
33
what are the regulatory genes in the lac operon ?
lac I - repressor protein - always activated , prevent transcription of lac Z and lac Y in the absence of lactose ( represses them )
34
what are the control elements in the lac operon ?
promoter - where RNA polymerase binds operator - where the repressor protein binds
35
what happens when the lac operon is switched off ?
1. no lactose 2. repressor protein ( lac I) binds to operator this also blocks the promoter slightly meaning that RNA polymerase cant bind 3. lac Z and lac Y are not expressed and proteins made for lactose utilisation aren't made 4. this is called down regulation
36
what happens when the lac operon is switched on ?
1. lactose is present 2. the lactose binds to the repressor this means it cant bind to the operator 3. the RNA polymerase can bind = lac Z and lac Y are active and use for lactose for respiration
37
what is post transcriptional level regulation ?
the editing of primary mRNA and the removal of introns to produce mature mRNA
38
what is splicing ?
in primary mRNA of eukaryotes: - removing introns - joining extrons to produce mature mRNA
39
what are introns ?
section of gene that does not code of an amino acid
40
what are extrons ?
section of gene that does code for amino acid
41
what is alternative splicing ?
extrons can be joined together in different combinations which results in different proteins being formed
42
what does post transcriptional control include ?
- addition of non protein groups - modifying amino acids folding or shortening of protiens - modification by cAMP
43
what is cAMP?
cyclic AMP is a molecule made from ATP ( using a catalyst adenyl cyclase ) which causes a cascade of reactions to regulate reactions it activates proteins by altering their 3D shape to become more or less active
44
what is an example of when cAMP is used?
once adenyl cyclase has catalysed the formation of ATP into cAMP the cAMP causes a chain of reactions from protein kinase allowing a cellular response eg. regulation of glycogen and lipid metabolism
45
what happens to the lac operon in the presence of low glucose ?
- low glucose means that the lac operon will be activated to use lactose - cAMP is produced and attaches to CAP which allows it to bind to the CAP site on the DNA strand - this helps RNA polymerase to bind ot the promoter and results in high levels of transcription of the genes ( lacZ and lacY )
46
what happens to the lac operon in the presence of high glucose ?
- high glucose means that the lac operon is not needed much - no cAMP is made so the CAP cant bind to DNA - this means there is low levels of transcription
47
what happens to the lac operon if : lactose and glucose are present ?
genes in the lac operon are minimally expressed as glucose can just be used
48
what happens to the lac operon if : lactose is present and glucose is not ?
up regulation of the lac operon using cAMP to allow more transcription of the enzymes needed
49
what happens to the lac operon if : lactose is absent and glucose is present ?
lac operon is switched off because lactose is not available and glucose can be used lactose is not available to bind to the repressor so it remains bound to the promoter preventing RNA
50
what happens to the lac operon if : lactose is absent and glucose is absent ?
lac operon is switched off because lactose is not available lactose is not available to bind to the repressor so it remains bound to the promoter preventing RNA no glucose available = no respiration !
51
how can cAMP change how the lac operon functions?
cAMP activates CAP ( also know as CRP ) and this increases the rate of transcription of structural genes for the lac operon or the opposite (post transcriptional control )
52
what is a body plan ?
basic structural layout of an organism they can be studied in terms of embryonic development or genetic regulation are controlled by ; genetics or environmental conditions meaning that internal and external stimulus can influence how genes that regulate the cell cycle are expressed
53
what are homeobox genes ?
genes which determine and control the development of organisms body plan they do this by coding for transcription factor proteins which bind to DNA to determine expression of other genes, genes controlling processes like : mitotic cell division, apoptosis, cell migration, regulating the cell cycle
54
what is a homeobox sequence ?
the specific 180 DNA base pairs that code for the transcription factor made
55
what's the homeodomain ?
the area on the transcription factor protein that was coded for by the homeobox sequence and is therefore 60 amino acids it folds into a specific shape to allow it to bind to DNA
56
what is the key word to describe the homeobox gene ?
highly conserved - the sequence in plants, animals and fungi are similar, unchanged over time - this is because the DNA binding regions must all have the same shape, mutations that occur can lead to not viable organisms, not favored by natural selection.
57
what is the definition for highly conserved ?
sequences have been maintained by natural selection
58
what are hox genes ?
a call of homeobox genes responsible for the correct positioning of body parts - regulate development of embryos along head tail axis - organised in hox clusters - collinearity
59
what does collinearity mean in terms of hox genes?
the linear order tot he hox genes in each cluster is directly related to the order of regions of the body they affect
60
how are homeobox genes regulated ?
gap genes and pair rule genes - these intern are regulated by maternally supplied mRNA from egg cytoplasm
61
what is apoptosis ?
programmed cell death
62
what are the stages of apoptosis ?
1. enzymes break down the cell cytoplasm 2. the cytoplasm becomes dense with tightly packed organelles, the CSM changes and small protrusions called blebs form 3. chromatin condenses, nuclear envelope breaks down and DNA breaks into fragments 4. cell breaks into vesicles that are ingested by phagocytes
63
why are mitosis and apoptosis important in controlling development of body plans?
constant replacing or destroying of cells throughout early development controls the development of body form in some cases cells are produced that are not needed and they must be destroyed eg. fingers and toes first develop as once unit and are separated by apoptosis
64
why is it important to control rate of apoptosis ?
if the rate is greater than rate of mitosis then cells are lost and degraded if the rate is higher than rate of mitosis then tumors form rates of apoptosis and mitosis must be equal
65
what are examples of internal stimuli that affect apoptosis and the cell cycle ?
- damage to DNA - phycological stress - release of hormones - RNA decay ect.
66
what are examples of external stimuli that affect apoptosis and the cell cycle ?
- change in light intensity and temp - pathogen attack - lack of nutrients - drugs ect.
67
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