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A Level Biology > Cellular Control > Flashcards

Cellular Control Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Proteome?

A

proteins being expressed by a cell

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2
Q

non coding DNA?

A
  • Junk DNA

* found in introns

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3
Q

what is a codon?

A

a base sequence on mRNA that codes for a single AA

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4
Q

What is an anticodon?

A

corresponding bse seq on tRNA

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5
Q

What is a mutation?

A

a change in the sequence of bases in DNA

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6
Q

Point mutation?

A

only 1 nucleotide is changed

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7
Q

Chromosome mutation?

A

multiple nucleotides, entire sections of chromosome or entire chromosome changed.
e.g. down syndrome - extra copy of a chromosome

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8
Q

3 types of point mutation?

A
  • Substitution
  • deletion
  • addition
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9
Q

substitution mutation?

A

where 1 base is replaced by another

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10
Q

deletion mutation?

A

where 1 or more bases are removed

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11
Q

addition mutation

A

where 1 or more bases are added

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12
Q

addition and deletion cause a

A

frame shift - as the genetic code is read as triplets, the frame shifts meaning the ‘right’ protein is not synthesised

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13
Q

the effec of mutations?

A

mutations can change the protein that is synthesised from the mutated section of DNA - the gene

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14
Q

Mutations can be:

A
  • neutral
  • harmful
  • beneficial
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15
Q

Neutral mutation?

A
  • have no effect on the structure and or function of the protein
  • (the AA coded for doesn’t change or the AA has very similar properties to the original AA)
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16
Q

Harmful mutations?

A
  • structure and function of the protein is changed so the organism is affected in a negative way
  • e.g. sickle cell anaemia, PKU
  • causes a selective disadvantage, decreasing chance of survival and decreasing chance of reproduction
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17
Q

beneficial mutations?

A

structure and function of the protein is changed so the organism is affected in a + way e.g. HIV resistance

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18
Q

sickle cell anaemia?

A
  • most common genetic disorder
  • mutation in the gene coding for Hb
  • sub of 1 base
  • thymine replaces adenine, making valine instead of glutamic acid on the beta chain
  • Usually, Hb soluble bc hydrophilic R groups are on the surface
  • but valine = hydrophobic so less soluble, causes Hb to stick together in low O2 conc
  • changes shape of E to spiky and less flexible
  • sickle cells block capillaries, starving tissues of O2
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19
Q

PKU?

A
  • genetic disorder caused by mutation in the gene coding for the enzyme PAH
  • PAH needed to convert phenylalanine to tryosine
  • when PAH deficient, phenylalanine accumulates
  • diet low in phenylalanine and high in tyrosine = treatment but there is no cure
  • heel prick test
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20
Q

beneficial mutations: lactose tolerance?

A
  • lactase breaks down lactose
  • body stop producing lactase after adolescence
  • diary farmers evolved genetic mutations that kept lactase active throughout life
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21
Q

beneficial mutations: HIV resistance?

A
  • CCR5A32 = 32 base pair deletion
  • results in non-functioning HIV receptor on T lymphocyte
  • HIV can’t bind to T lymphocyte and infect them
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22
Q

mutations occur?

A

all of the time, randomly in the genome

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23
Q

mutagens?

A
  • inc chance of mutation occuring

* are chemical, physical or biological agents that cause mutations

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24
Q

chemical mutagens?

A

e.g. deaminating agents - chemically altered bases in DNA

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25
Q

physical mutagens?

A

e.g. ionising radiation

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26
Q

biological mutagens?

A

viruses may insert DNA into genome, changing base seq

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27
Q

ways to control gene expression?

A
  • transcriptional control
  • post transcriptional control
  • post translational control
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28
Q

transcriptional control?

A

• controlling rate at which gene(s) is transcribed, or whither they are transcribed or not e.g. lac operon, epigenetics

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29
Q

post translational control?

A

• processing and modification of polypeptide chains formed by translation (Golgi)

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30
Q

post transcriptional control?

A

processing, modification and editing of mRNA IMMEDIATEDLY AFTER TRANSCRIPTION

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31
Q

What is an operon?

A

set of genes and regions of DNA that control the transc of structural genes

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32
Q

lac operon occurs in?

A

bacterial cells, it’s an inducable system

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33
Q

structural genes?

A

are expressed

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34
Q

control regions?

A

don’t code for proteins

35
Q

structural genes are switched on when (lac operon)

A

in the presence of lactose, off in absence

36
Q

Components in the lac operon?

A
  • Lac I gene
  • Promoter region
  • Operator region
  • Lac Z
  • Lac Y
  • Lac A gene
37
Q

what are the structural genes?

A

Lac Z, Y and A

38
Q

What does the lac I gene do?

A

codes for lac repressor protein which binds to operator region. Is expressed all of the time

39
Q

what does the lac Z gene do?

A

codes for lactase (beta galactosidase)

40
Q

what does the lac Y gene do?

A

codes for lactose permease, a membrane protein that inc the permeability of the bacterial cell membrane to lactose

41
Q

lac A gene role?

A

no direct role, but codes for beta galactosidase transacetylase - no direct role

42
Q

Control region [lac operon]?

A
  • promoter region
  • operator region
  • found upstream of structural genes
43
Q

promoter region?

A

• where RNAP binds to transcribe the structural genes (every gene has 1)

44
Q

operator region?

A

• where the lac repressor protein can bind, locking binding of RNA P to promoter region and transcription of the structural genes

45
Q

lac operon formed from?

A

control region and 3 structural genes

46
Q

non-coding DNA is now called

A

introns

47
Q

if a gene is expressed?

A

it’s transcribed and translated

48
Q

in the lac operon, lactose acts as a ?

A

transcription factor bc controls transcription

49
Q

Epigenetics means

A

above or on top of the genome

50
Q

DNA in eukaryotes?

A
  • tightly wound around histone proteins forming chromatin

* the tighter this coiling, the less likely a gene is to be transcribed and vv

51
Q

how can transcription be increased or decreased?

A
  • histone proteins and DNA can be modified to inc or decrease tightness of coiling and therefore increase or transcription of genes
  • e.g. acetylation
  • e.g. methylation
52
Q

acetylation of histones?

A

causes loosening of coiling

53
Q

methylation of histones?

A

coiling becomes tighter, meaning RNAP can’t access gene easily, rate of gene expression = low

54
Q

acetyl and methyl groups are e.g.s of ?

A

epigenetic tags

55
Q

what are epigenetic tags?

A

chemicals that don’t change the seq of bases in DNA but change the way the genetic code is read

56
Q

epigenetic tags can be

A

picked up during an individual’s life and can be passed onto the next gen

57
Q

Passing of epigenetic tags onto offspring?

A
  • during indiv’s life, envir can cause histone proteins and DNA to become modified by addition/ removal of epigenetic tags and gene expression can change
  • e.g. diet, exercise, physical activity, stress
  • most tags removed from parental genome after fert but some remain imprinted
  • offspring can inherit something learned by parents
  • no change in DNA seq, but a change in epigenome - the way in which genes are expressed
58
Q

post transvriptional modification?

A
  • pre-mRNA is the 1st product of transc
  • modified to form mature mRNA, which can then be transl
  • modified nucleotide ‘cap’ is added to 5’ end of pre-mRNA
  • Tail added to 3’ end
  • stabilises molecule, and aids ribosome binding
  • then, pre-mRNA spliced
59
Q

splicing?

A
  • removes non coding sections - introns

* exons remain and expressed

60
Q

splicing means that

A

mRNA can produce more than 1 protein from the same gene

61
Q

Alternate splicing ⭐

A

exons are always in order, never shuffled

62
Q

Post translational modification occurs?

A

after the ribosome has synthesised the polypeptide chain the molecule is modified

63
Q

How can the polypeptide chain be modified?

A
  • non-protein groups can be added, like CHO chains - often in Golgi
  • Structure of indiv AA changed - changes overall folding of the protein
  • folding and shortening of proteins
  • modification by cAMP
64
Q

cAMP?

A
  • 2nd messenger, many regulatory effects
  • can activate proteins after transl
  • e.g. activation of enzyme PKA which starts off the amplification cascade
65
Q

control of development?

A

by homeobox genes

66
Q

homeobox genes?

A
  • control body plan
  • same set of genes used by all animals
  • set of genes w very similar base seq shared by wide variety of organisms - plants, animals, fungi
67
Q

what is a hox gene?

A

1 homeobox gene in an animal

68
Q

what is the homeodomain?

A

the seq of AA coded for by homeobox genes

69
Q

how do homeobox genes provide good evidence for evolution?

A

v similar, shows that these organisms evolved from a common ancestor

70
Q

How do homeobox genes work?

A
  • code for transcription factors

* which control gene expression of other genes

71
Q

what is a homeobox?

A

the base sequence

72
Q

proteins containing the homeodomain…

A

can bind to DNA and act as transcription factors, controlling the expression of whole sets of other genes. These genes control the body plan of the organism.

73
Q

how do homeobox genes determine the body plan of an organism?

A

v active during early development, controlling gene expressed of 1000s of other genes which determine the body plan of an organism

74
Q

if a homeobox gene is mutated?

A

• the right thing will still develop, because the homeobox gene is still being expressed just in the wrong place

75
Q

consequences of a mutation in a homeobox gene ?

A
  • usually fatal so mutations rarely passed onto next gen
  • means the base sequence of the genes has hardly changed - is highly conserved
  • and very similar between diff organisms
76
Q

Homeobox genes code for transcription factors that?

A

can bind to the promoter region of sets of genes affecting their expression

77
Q

proteins coded for by homeobox genes have a wide variety of effects…

A
  • controlling metabolic pathways
  • synthesising structural proteins
  • setting off cascades of other reaction, eventually determining an aspect of the body plan of an organism e.g development of eyes
78
Q

Homeobox genes also control?

A
  • mitosis

* apoptosis - programmed cell death

79
Q

2 ways through which homeobox genes control an organism’s BP?

A
  • controlling gene expression

* controlling mitosis and apoptosis

80
Q

Stages of apoptosis?

A
  1. apoptosis is triggered by external/ internal stimuli
  2. complex cascades of metabolic reactions cause disintegration of cytoskeleton
  3. Cell loses its structure and organelles fragment
    • blebs form
    • cells breaks up into apoptotic bodies which are engulfed by phagocytes and molecules recycled
81
Q

Factors affecting expression of HG?

A
  • stages of development or age of organism
  • abiotic stressed e.g. LI, T
  • Psychological stress
  • Presence of hormones
  • Other chemicals e.g. drugs
82
Q

Nurturing rats - e.g. of epigenetic tags

A

ewfw

83
Q

epigenetics is an e.g. of ?

A

transcriptional control

84
Q

E.g. of epigenetics

A
  • nurturing rays
  • nurtured = calm adults
  • little nurturing = anxious
  • when the GR gene is active, it produces a protein that helps body relax
  • licking activates GR gene, DNA loosens transcription can occur, so GR protein can be produced
  • GR protein binds to cortisol causing cell to send out calming sigal

A Level Biology (28 decks)

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