Genetics of living systems Flashcards
1
Q
mutation
A
a naturally random change in the sequence of bases in DNA of an organism
2
Q
mutagen
A
chemical, physical or biological agents that increase the rate of mutations
3
Q
three examples of mutagens (chemical, physical, biological)
A
- carcinogenic chemicals (tobacco smoke etc)
- high energy radiation (UV, x-rays)
- viruses (insert viral DNA
4
Q
how does high energy radiation cause mutations
A
waves break parts of DNA strands leaving gaps in bases
5
Q
three outcomes of mutations
A
- neutral
- harmful (damages or kills cell/cancerous cells)
- beneficial (increase generic biodiversity)
6
Q
can mutations be inherited?
A
only when the mutation occurs during meiosis/in a gamete
7
Q
four types of gene mutation
A
- insertion
- deletion
- substitution
- inversion
8
Q
insertion
A
an additional base inserted into the base sequence which shifts the reading frame along (forwards)
9
Q
deletion
A
a base has been missed from the base sequence which shifts the reading frame backwards
10
Q
substitution
A
an incorrect base has been used which may change the amino acid that that specific codon codes for
11
Q
inversion
A
bases are inserted backwards (which may affect however many codons are inverted)
12
Q
three types of effects of mutations (and what are they)
A
- silent (no effect)
- nonsense (one or more amino acid affected)
- missense (doesn’t code for anything)
13
Q
which types of mutations are frameshift mutations?
A
- insertion
- deletion
14
Q
gene mutation vs chromosome mutation
A
gene mutation occurs within a single gene
chromosome mutation affects one or more chromosomes
15
Q
four types of chromosomes mutations
A
- duplication
- deletion
- inversion
- translocation
16
Q
chromsome deletion
A
a section of chromosome breaks off
17
Q
chromosome duplication
A
section of a chromosome duplicated and added onto that same chromosome
18
Q
chromosome inversion
A
a section of chromosome breaks off, is reversed and put back on the chromosome
19
Q
chromosome translocation
A
section of a chromosome breaks off and joins another non-homologous chromosome
20
Q
monomers of lactose
A
glucose + galactose
21
Q
enzymes made in the lac operon (and what are they)
A
- lactose permease (transport protein)
- β-galactosidase (enzyme breaks down lactose)
22
Q
operon
A
DNA with structural genes that code for proteins and control sites (operator and promoter)
23
Q
why do bacteria breakdown lactose?
A
to produce glucose to use as a respiratory substrate (glucose is a primary respiratory substrate as oppose to lactose)
24
Q
why is the lac operon an “inducable” process
A
it is induced by the presence/absence of lactose
25
regions on the lac operon
- regulatory gene
- control sites
--> operator + promoter
- structural gene
26
regulatory gene
section of the operon that codes for a repressor protein
27
promoter
section of the operon where RNA polymerase binds
28
operator
section of the operon where the repressor protein binds (can switch structural genes on and off)
29
structural gene (of the lac operon)
codes for lactose permease and β galactosidase
30
what happens in the lac operon when lactose is absent?
- regulatory gene transcripted and translated to form a repressor protein
- repressor protein binds to operator region
- RNA polymerase binds to promoter region
--> cannot transcript structural genes (blocked by repressor)
--> no mRNA produced
--> no specific amino acid sequence
--> no lactose permease or β-galctosidase
31
what is different in the lac operon when lactose is present?
- lactose binds to repressor protein
- causes a confirmational change
- repressor can no longer bind to operator region
- RNA polymerase can bind to promoter and transcript structural genes
32
four types of gene control
- transcriptional (gene switching on/off)
- post-transcriptional (mRNA modified)
- translational (translation stopped or started)
- post-translational (proteins modified to change functions)
33
gene expression
conversion of information encoded in a gene into a functional product (protein or RNA)
34
gene regulation
wide range of mechanisms used by cells to increase or decrease rate of transcription
35
transcription factors
proteins that affect the rate of transcription by binding to DNA at specific locations
36
why can splicing only occur in eukaryotes?
prokaryotes don't have introns
37
chromatin
diffused, loosely packaged (not condensed) DNA
38
two types of chromatin
heterochromatin - tightly sound around histones
- euchromatin - loosely wound around histones
39
when are the two types of chromatin present?
heterochromatin - during cell division
euchromatin - during interphase
40
three types of transcriptional gene regulation
- chromatin remodelling
- histone modification
- cAMP
41
two types of histone modification (and what they do)
acetylation or phosphorylation:
- reduces +ve charge on histones
- -ve DNA winds more loosely around histones
- rate of transcription increases
methylation:
- histones become more hydrophobic
- DNA winds more tightly around histones
- rate of transcription decreases
42
three types of post-transcriptional gene regulation
- splicing
- RNA editing (point/deliberate mutations to alter protein structure)
- RNA processing
43
splicing
introns removed from primary mRNA to form mature mRNA (only in EUKARYOTES)
44
three types of translational gene regulation (and what they do)
- degradation of mRNA (decreases rate of transcription)
- binding of inhibitory proteins to mRNA (prevents binding to ribosome)
- activation of initiation factors (aid binding of mRNA to ribosomes)
45
three types of post-translational gene regulation
- addition of non-protein groups (carbs, lipids etc)
- modifying amino acids and bond formations (disulfide bridges etc)
- folding/ shortening proteins
46
epigenetics
external control of genetic regulation
47
how does cAMP affect transcription
- low glucose concentrations increase cAMP concentrations
- cAMP binds to CRP (cAMP receptor protein)
- increases rate of transcription
48
what is RNA processing?
- cap (modified nucleotide added to the 5' end
- tail (long chain of adenine nucleotides) added to the 3' end
49
how does RNA processing affect rate of transcription?
- stabilises mRNA
- delays degradation of mRNA
- aids binding of mRNA and ribosomes
50
protein kinases
- enzymes that catalyse phosphorylation of proteins
--> changes tertiary structure and function of proteins
--> activates enzymes (which affect cell activity so cell activity can be regulated)
51
what activates PKA?
cAMP (secondary messenger that triggers a protein messenger cascade)
52
homeobox
a DNA sequence that codes for a transcription factor
53
homeobox sequence
180bp (60 amino acids) and regulates patterns of anatomical development in animals, fungi and plants by coding for a protein transcription factor
54
which kingdoms have homeobox sequences?
- animals
- plants
- fungi
55
homeobox gene
any gene containing a homeobox sequence
56
what do all homeobox sequences have in common?
they are all highly conserved (remain relatively unchanged when travelling back in evolutionary time
57
why are homeobox sequences highly conserved?
mutations in homeobox seuqneces make an organisms non-viable so are not favoured by natural selection
58
what are homeobox genes responsible for in embryos?
genetic control of development of body plans
59
two parts of the body plan that homeobox genes control
- polarity (distinct head and tail end)
- segmentation (limbs, abdomen, thorax, organs)
60
how many homeobox genes control invertebrate segments?
8 homeobox genes
61
colinearity
sequence of genes in chromosomes corresponds to sequence of body parts
62
homeosis
one part of a developing embryo transforms into another (e.g. mutation causing legs to grow instead of antennae)
63
Hox genes
an important subset/type of homeobox genes (other subsets control different things like Pax genes control eye and nervous system development)
64
what do Hox genes control?
Identity of embryonic body regions along the anterior-posterior axis (head-tail)
65
what transcription factors do Hox genes code for?
transcription factors that activate genes to promote mitosis, apoptosis and cell migration
66
what are groups of Hox genes called?
Hox clusters
67
Hox clusters
groups of Hox genes that are physically close together on a chromosome
68
how many Hox clusters for vertebrates have (and how many Hox genes does each contain)?
4 Hoc clusters found on DIFFERENT CHROMOSOMES (containing 9-12 Hox genes)
69
two genes that regulate Hox genes?
- gap genes
- pair rule genes
70
what regulates gap genes and pair rule genes?
maternal mRNA from the egg cytoplasm
71
two pathways leading to apoptosis
- internal signaling pathway
- external signalling pathway
72
external signalling of apoptosis
- nearby cells release signalling molecules which bind to specific receptors
- initiates signal transduction
- expresses genes which code for proteins which carry out apoptosis
73
internal signalling of apoptosis
- series of protein-protein interactions act as signals which trigger apoptosis
73
three reasons why apoptosis occurs
- destroy cells with harmful mutations (prevent tumors)
- shape organisms (e.g. remove webs from between fingers)
- stimulates mitosis (tissue repair and shape organisms)
74
stages of apoptosis
- enzymes breakdown cytoskeleton
- cytoplasm becomes more dense with tightly packed organelles
- plasma membrane changes and forms blebs (small protrusions)
- chromatin condenses, nuclear envelope breaks down and DNA fragments
- cell breaks into vesicles
- vesicles ingested by phagocytic cells (phagocytosis)
75
why are broken down cells ingested?
prevent debris (mutated enzymes etc) from damaging other cells and tissues
76
four examples of cell signalling molecules
- hormones
- cytokines
- growth factors
- nitric oxide
77
how does nitric oxide cause apoptosis?
- makes inner mitochondrial membrane more permeable to H+ ions
- no H+ gradient (diffuse through membrane until equilibrium is reached as opposed to beings actively pumped across)
- inhibits chemiosomosis
78
four ways in which transcription factors can prevent transcription
- preventing H bonds between base pairs from breaking
- preventing RNA polymerase from binding to DNA
- preventing RNA polymerase moving along gene
- preventing H bond formation between DNA bases and free RNA nucleotides
- preventing formation of phosphodiester bonds between adjacent free RNA nucleotides
79
what enzymes remove RNA introns?
endonucleases
80
how can splicing create different proteins?
exons can be joined back together in different orders
81
two types of transcription factors
- activators (encourage RNA polymerase to bind)
- repressors (prevent RNA polymerase from binding)
