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biology M6 > cellular control > Flashcards

cellular control Flashcards

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1
Q

what is regulation of gene expression

A
  • how genes are switched on/off
  • how they’re activated at the correct time
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2
Q

what 4 stages can regulation of gene expression occur in

A
  • transcription
  • post-transcription
  • translation
  • post-translation
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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
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4
Q

what is a point mutation

A
  • only one nucleotide is affected
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5
Q

what is substitution

A
  • single nucleotide changes
  • this may code for a different amino acid as a different codon is produced
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6
Q

what does insertion/deletion cause

A
  • a frameshift in the DNA sequence
  • this changes every successive codon from the point of mutation
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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
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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
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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
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10
Q

what is a mutagen

A
  • a chemical ,physical or biological agent which causes mutations
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11
Q

what is an example of a physical mutagen and what does it do

A
  • ionising radiations
  • break one or both DNA strands
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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
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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
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12
Q

what is a silent mutation

A
  • neutral
  • do not change any proteins or the activity of the proteins synthesised
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12
Q

what is a nonsense mutation

A
  • results in the coding of a stop codon instead of a normal codon
  • shortens the protein
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13
Q

what is a missense mutation

A
  • incorporation of an incorrect amino acid into the primary structure of a protein
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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
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15
Q

what is duplication in terms of changes in the structures of chromosomes

A
  • sections are duplicated on a chromosome
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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
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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
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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
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19
Q

what is gene regulation

A
  • expressing genes only when they are needed which prevents vital resources from being wasted
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20
Q

how are genes regulated at the transcription stage

A
  • genes are turned on or off
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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
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22
Q

how are genes regulated at the post-translation stage

A
  • proteins can be modified after synthesis which changes their functions
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23
Q

how are genes regulated at the translation stage

A
  • translation can be stopped or started
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24
Q

what is a chromatin

A
  • DNA complex that is wound around histones in order to be packed into the nucleus of a cell
25
Q

what is a heterochromatin and a euchromatin

A
  • a heterochromatin is tightly wound DNA causing chromosomes to be visible during cell division
  • a euchromatin is loosely wound DNA present during interphase
26
Q

how does histones control transcription

A
  • 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
Q

why does DNA coil around histones

A
  • DNA is negatively charged and histones are positively charged
28
Q

what is an operon

A
  • group of genes that are under the control of the same regulatory mechanism and are expressed at the same time
29
Q

what is a lac operon

A
  • 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
Q

what does the regulatory gene code for

A
  • repressor protein
31
Q

what does the repressor protein do in the absence of lactose

A
  • prevents transcription
  • binds to the operator which prevents RNA polymerase from binding to the promoter and beginning transcription
  • this is down regulation
32
Q

what happens when lactose is present in the lac operon

A
  • 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
Q

what does the binding of cAMP do to the rate transcription

A
  • increases it
34
Q

how does cAMP bind

A
  • only possible if CRP is bound to cAMP
35
Q

what lowers the levels of cAMP and what effect does this have

A
  • transport of glucose into E-coli cell
  • reduces metabolism of lactose
36
Q

what is RNA process in terms of post-transcriptional control

A
  • 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
Q

what is splicing

A
  • introns are removed (non-coding DNA) and exons are joined together
38
Q

what is RNA editing and what stage doe sit occur in

A
  • post-transcription
  • addition, deletion or substitution of mRNA
  • increases range of proteins taht are produced
39
Q

what occurs during translational control

A
  • 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
Q

what are protein kinases and which stage are they used in

A
  • enzymes that catalyse the addition of phosphate groups
  • changes the tertiary structure and function of the protein
  • often activated by cAMP
  • translational
41
Q

what occurs during the post-translational stage

A
  • 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
Q

what is morphogenesis

A
  • regulation of the pattern of anatomical development
43
Q

what are homeobox genes

A
  • a group of genes which all contain a homeobox
44
Q

what is a homeobox

A
  • section of DNA coding for a part of the protein that is highly conserved in plants.animals and fungi
45
Q

how many base pairs long is a homeobox

A
  • 180
46
Q

how many amino acids long is the part of the protein that is coded for by a homeobox

A
  • 60
47
Q

what is a homeodomain

A
  • binds to DNA and switches genes on or off
48
Q

what are Hox genes

A
  • group of homeobox genes that are only present in animals
49
Q

what are Hox genes responsible for

A
  • correct positioning of body parts
50
Q

how many gene clusters do mammals have on different chromosomes

A
  • 4
51
Q

how many hox genes do humans have altogether

A
  • 39
52
Q

how are body plans usually represented

A
  • cross-sections through the organism showing the arrangement of tissue layers
53
Q

what is a common feature of animals

A
  • segmented
  • have become more adapted and specialised over time
54
Q

what is a somite

A
  • segments in embryo that have developed individual vertebrae and associated structures
55
Q

what is radical symmetry

A
  • no left and right
  • only top and bottom
56
Q

what is bilateral symmetry

A
  • left and right
  • head and tail instead of top and bottom
57
Q

what is asymmetry

A
  • no lines of symmetry
58
Q

what is apoptosis

A
  • programmed cell death
59
Q

what does apoptosis do

A
  • shapes different body parts by removing unwanted cells and tissues
60
Q

what does cells undergoing apoptosis release

A
  • chemical signals which stimulate mitosis and cell proliferation leading to the remodeling of tissues
61
Q

what is apoptosis and mitosis regulated by

A
  • hox genes
62
Q

what are the factors that affect expression of regulatory genes

A
  • temperature or high light intensity
  • release of hormones of psychological stress
  • drugs
63
Q

what is stress

A
  • condition produced when the homeostatic balance within an organism is upset

biology M6 (6 decks)

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