cellular control Flashcards
1
Q
what is regulation of gene expression
A
- how genes are switched on/off
- how they’re activated at the correct time
2
Q
what 4 stages can regulation of gene expression occur in
A
- transcription
- post-transcription
- translation
- post-translation
3
Q
what is a mutation of genes
A
- change in the sequence of bases in DNA
- caused by substitution, deletion or insertion of one or more nucleotides
4
Q
what is a point mutation
A
- only one nucleotide is affected
5
Q
what is substitution
A
- single nucleotide changes
- this may code for a different amino acid as a different codon is produced
6
Q
what does insertion/deletion cause
A
- a frameshift in the DNA sequence
- this changes every successive codon from the point of mutation
7
Q
how might a mutation have no effect
A
- the same amino acid is coded for
- no change in the phenotype of the organism
- proteins are normally functioning
8
Q
how might a mutation have a damaging affect
A
- phenotype may be affected in a negative way because essential proteins may no longer be synthesised or may be non-functioning
9
Q
how might a mutation be beneficial
A
- very rare
- may involve a new and useful characteristic in the phenotype to be coded for
10
Q
what is a mutagen
A
- a chemical ,physical or biological agent which causes mutations
11
Q
what is an example of a physical mutagen and what does it do
A
- ionising radiations
- break one or both DNA strands
12
Q
what is a chemical mutagen and what does it do
A
- deaminating agents
- chemically alter bases in DNA such as converting uracil to cytosine in DNA
12
Q
what is a biological mutagen and what does it do
A
- alluylating agents
- methyl or ethyl groups are attached to bases which would cause incorrect base pairing
12
Q
what is a silent mutation
A
- neutral
- do not change any proteins or the activity of the proteins synthesised
12
Q
what is a nonsense mutation
A
- results in the coding of a stop codon instead of a normal codon
- shortens the protein
13
Q
what is a missense mutation
A
- incorporation of an incorrect amino acid into the primary structure of a protein
14
Q
what is deletion in terms of change sin the chromosome structure
A
- section of chromosome breaks off and is lost within the cell
15
Q
what is duplication in terms of changes in the structures of chromosomes
A
- sections are duplicated on a chromosome
16
Q
what is translocation in terms of the structure of chromosomes
A
- section of one chromosome breaks off and joins another non-homologous chromosome
17
Q
what is inversion in terms of the structure of chromosomes
A
- section of chromosome breaks off is reversed and joins back onto the chromosome
18
Q
what are house keeping genes
A
- genes that code for enzymes which are necessary for reactions in the metabolic pathways and are constantly needed
19
Q
what is gene regulation
A
- expressing genes only when they are needed which prevents vital resources from being wasted
20
Q
how are genes regulated at the transcription stage
A
- genes are turned on or off
21
Q
how are genes regulated at the post-transcription stage
A
- mRNA can be modified which regulates translation and the types of protein produced
22
how are genes regulated at the post-translation stage
- proteins can be modified after synthesis which changes their functions
23
how are genes regulated at the translation stage
- translation can be stopped or started
24
what is a chromatin
- DNA complex that is wound around histones in order to be packed into the nucleus of a cell
25
what is a heterochromatin and a euchromatin
- a heterochromatin is tightly wound DNA causing chromosomes to be visible during cell division
- a euchromatin is loosely wound DNA present during interphase
26
how does histones control transcription
- transcription of genes isn't possible when DNA is tightly coiled because RNA polymerase can't access the genes
- histones can be modified to increase of decrease the degree of packing
- addition of acetyl groups or phosphate groups reduces the positive charge in the histones meaning DNA is less tightly wound
- addition of methyl groups makes the histones more hydrophobic so they bind more tightly
27
why does DNA coil around histones
- DNA is negatively charged and histones are positively charged
28
what is an operon
- group of genes that are under the control of the same regulatory mechanism and are expressed at the same time
29
what is a lac operon
- group of 3 genes involved in the metabolism of lactose
- involves structural genes that code for 3 enzymes and are transcribed onto a single long molecule of mRNA
30
what does the regulatory gene code for
- repressor protein
31
what does the repressor protein do in the absence of lactose
- prevents transcription
- binds to the operator which prevents RNA polymerase from binding to the promoter and beginning transcription
- this is down regulation
32
what happens when lactose is present in the lac operon
- lactose binds to the repressor protein which alters it's shape so it can no longer bind to the operator
- RNA polymerase is able to bind to the promoter and transcription begins
33
what does the binding of cAMP do to the rate transcription
- increases it
34
how does cAMP bind
- only possible if CRP is bound to cAMP
35
what lowers the levels of cAMP and what effect does this have
- transport of glucose into E-coli cell
- reduces metabolism of lactose
36
what is RNA process in terms of post-transcriptional control
- modifies pre-mRNA into modified mRNA so it can bind to ribosomes
- a cap is added to the 5' end and a tail is added to the 3' end
- helps to stabilise mRNA
- splicing
37
what is splicing
- introns are removed (non-coding DNA) and exons are joined together
38
what is RNA editing and what stage doe sit occur in
- post-transcription
- addition, deletion or substitution of mRNA
- increases range of proteins taht are produced
39
what occurs during translational control
- degradation of mRNA - more resistant molecules last longer in the cytoplasm = greater quantity of proteins synthesised
- binding of inhibitory proteins to mRNA prevents binding to ribosomes
- activation of initiation of factors which promote binding of mRNA to ribosomes
40
what are protein kinases and which stage are they used in
- enzymes that catalyse the addition of phosphate groups
- changes the tertiary structure and function of the protein
- often activated by cAMP
- translational
41
what occurs during the post-translational stage
- modifications to synthesised proteins
- addition of non-protein groups e.g. lipids
- modifying amino acids and the formation of bonds
- folding and shortening of proteins
- modification of cAMP
42
what is morphogenesis
- regulation of the pattern of anatomical development
43
what are homeobox genes
- a group of genes which all contain a homeobox
44
what is a homeobox
- section of DNA coding for a part of the protein that is highly conserved in plants.animals and fungi
45
how many base pairs long is a homeobox
- 180
46
how many amino acids long is the part of the protein that is coded for by a homeobox
- 60
47
what is a homeodomain
- binds to DNA and switches genes on or off
48
what are Hox genes
- group of homeobox genes that are only present in animals
49
what are Hox genes responsible for
- correct positioning of body parts
50
how many gene clusters do mammals have on different chromosomes
- 4
51
how many hox genes do humans have altogether
- 39
52
how are body plans usually represented
- cross-sections through the organism showing the arrangement of tissue layers
53
what is a common feature of animals
- segmented
- have become more adapted and specialised over time
54
what is a somite
- segments in embryo that have developed individual vertebrae and associated structures
55
what is radical symmetry
- no left and right
- only top and bottom
56
what is bilateral symmetry
- left and right
- head and tail instead of top and bottom
57
what is asymmetry
- no lines of symmetry
58
what is apoptosis
- programmed cell death
59
what does apoptosis do
- shapes different body parts by removing unwanted cells and tissues
60
what does cells undergoing apoptosis release
- chemical signals which stimulate mitosis and cell proliferation leading to the remodeling of tissues
61
what is apoptosis and mitosis regulated by
- hox genes
62
what are the factors that affect expression of regulatory genes
- temperature or high light intensity
- release of hormones of psychological stress
- drugs
63
what is stress
- condition produced when the homeostatic balance within an organism is upset
