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Biology Module 6 > 6.1.1 Cellular Control > Flashcards

6.1.1 Cellular Control 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 3 reasons why mutation might occur

A

substitution
deletion
insertion
- of one or more nucleotides or base pairs within a gene

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3
Q

what is point mutation

A

when only one nucleotide is affected by mutation

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4
Q

what happens in a substitution mutation

A
  • changes the codon in which the nucleotide has been substituted in
  • if new codon codes for a different amino acid, this will change the primary structure of the protein
  • but genetic code is degenerate, so might still code for the same amino acid
  • so no change to protein synthesised
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5
Q

when will a substitution mutation be important, and what is this based on

A
  • depends on the position and involvement of the amino acid in R-group interactions within the protein
  • if for an enzyme, amino acid might play important role in the active site, so may not function any longer
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6
Q

what do insertion and deletion mutations result in

A

a frameshift mutation

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7
Q

explain a frameshift mutation

A
  • as genetic code is read/transcribed in non-overlapping triplets
  • when you add or remove a nucleotide
  • this will move the reading frame of sequence bases
  • so every successive codon will be changed from the point of mutation
  • still takes place if multiple are added, unless a multiple of 3 is changed
  • will not change the reading frame, but the protein formed will still be changed (lost or gained new amino acid)
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8
Q

what is the effects of mutations

A

no effect
damaging
beneficial

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9
Q

what happens if there is a no effect mutation

A
  • no effect on phenotype
  • as normally functioning amino acids are still synthesised
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10
Q

what happens if there is a damaging mutation

A
  • when proteins are no longer synthesised or are non-functional
  • can interfere with essential processes
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11
Q

what happens if there is a beneficial mutation

A
  • protein synthesised with have a new and useful characteristic in phenotype
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12
Q

when do mutations occur

A

spontaneously, often during DNA replication

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13
Q

what are the rate of mutations increased by

A

mutagens

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14
Q

what are mutagens

A

chemical, physical or biological agent which causes a mutation

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15
Q

what are some examples of mutagens

A
  • ionizing radiation such as x-rays
  • deaminating agents
  • alkylating agents
  • base analogs
  • viruses
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16
Q

what are chromosome mutations

A
  • affect the whole chromosome or number of chromosomes within a cell
  • can be silent or affecting
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17
Q

what are the types of chromosome mutations

A
  • deletion, where a section of chromosome breaks off and is lost within a cell
  • duplication, where sections of the chromosome get repeated
  • translocation, where a section of one chromosome breaks off and joins another non-homologous chromosome
  • inversion, where a section of chromosome breaks off, is reversed, and joins back
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18
Q

why is gene regulation important

A
  • the entire genome of an organisms is present in every prokaryotic/eukaryotic cell with nucleus
  • need to regulate which genes are actually needed, so can turn on or off genes and control the rate of product synthesis on demand
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19
Q

what is the basic difference between gene regulation in prokaryotes and eukaryotes

A
  • prokaryotes only have to respond to changes in the external environment
  • multicellular organisms also have to respond to internal conditions, and is important for cells to specialise
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20
Q

what are the different stages of cell regulation

A

transcriptional (genes turned on and off)

post-transcriptional (mRNA can be modified which regulates translation)

translational (can stop or start translation)

post-translational ( proteins being modified after translation to change their functions)

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21
Q

explain the relationship between DNA, histones and chromatin

A
  • DNA is a very long molecule
  • wound around proteins called histones in eukaryotic cells
  • resulting DNA/protein complex is called chromatin
22
Q

how is chromatin remodelling an example of transcriptional regulation

A
  • heterochromatin is tightly wound DNA which causes chromosomes to be visible during cell division
  • euchromatin is loosely wound DNA present during interphase
  • transcription of genes is not possible when DNA is tightly wound as RNA polymerase cannot access the genes
  • DNA which is loosely wound can be easily transcribed
  • explains why protein synthesis does not occur during cell division but interphase
23
Q

what is epigenetics

A

control of gene expression by the modification of DNA

24
Q

how does histone modification act as a transcriptional regulation factor

A
  • histones can be changed to increase or decrease the degree of packing
  • DNA packs around histones because they are positively charged and it is negative
  • can add acetyl groups (acetylation) or phosphate groups (phosphorylation) to reduce positive charge, so DNA coils less likely and certain genes can be transcribed
  • can add methyl (methylation) groups which makes histones more hydrophobic, bind to each other more tightly and DNA coils more tightly, preventing transcription of certain genes
25
Q

what is an operon

A

a group of genes that are under the control of the same regulatory mechanism and are expressed at the same time
- more common in prokaryotes than eukaryotes as they are smaller and simpler genomed

26
Q

why are operons efficient

A

if a certain gene product is not needed, then all of the genes involved can be switched off

27
Q

what is the preferred respiratory substrate of many bacteria, and if not available, what is used

A
  • glucose, as easy to metabolise
  • if not, lactose will be used
28
Q

what does the lac operon consist of

A
  • a promoter region (where RNA polymerase binds)
  • an operator region (where the repressor protein binds)
  • structural genes lac YZA
  • regulatory gene Lac I a short distance away
29
Q

what can be used to describe lac Y/Z/A

A

structural genes, as they code for 3 enzymes
- B-galactosidase, lactose permease and transacetylase
- transcribed onto a single long molecule of mRNA

30
Q

what is the regulatory gene present in the lac operon

A

LacI
- located near the operon and codes for the repressor protein - the transcription factor
- that prevents the transcription of the structural genes in the absence of lactose

31
Q

what happens in the absence of lactose

A
  • repressor protein binds to the operator region
  • prevents RNA polymerase from binding to the promoter
  • blocks transcription, meaning genes XYZ cannot be expressed, resources not wasted
32
Q

what happens in the presence of lactose

A
  • lactose binds to repressor protein
  • changes its shape, so can no longer bind to operator region
  • means that RNA polymerase can bind to the promoter region
  • and begin transcription
33
Q

what are examples of post-transcriptional control of gene regulation

A
  • pre-mRNA is modified forming mature mRNA before it can bind to ribosome
  • a cap (modified nucleotide) is added to 5’ end and tail (long chain of adenine nucleotide) is added to the 3’ end - help to stabilise mRNA and help with ribosome binding
  • SPLICING: RNA is cut at specific point, with introns (non-coding DNA) is removed and exons are joined
  • both WITHIN THE NUCLEUS
  • RNA editing also occurs like point mutations , resulting in synthesis of different proteins with different functions
  • increases the range of proteins that can be produced from a single mRNA molecule
34
Q

what is the role of cyclic AMP (cAMP)

A
  • binding of RNA polymerase still results in a slow transcription rate
  • not enough to properly metabolise lactose at rate needed
  • can be sped up by binding of a cAMP repressor protein CRP, which only works when bound to cAMP
  • ( a secondary messenger)
  • more glucose = less cAMP = less lactose metabolism
35
Q

what are examples of translational control

A
  • degradation of mRNA= more resistant the molecule, longer it will last in cytoplasm, greater quantity of protein synthesised
  • binding of inhibitory proteins to mRNA prevents it binding to ribosomes and synthesis of proteins
  • activation of initiation factors which aid in binding of mRNA to ribosomes
36
Q

explain protein kinases as translational control

A
  • protein kinases are enzymes that catalyse the addition of phosphate groups to proteins
  • changes the tertiary structure
  • so the function
  • and many enzymes are activated by phosphorylation, so an important regulator or cell activity
37
Q

what examples of post-translational control

A
  • addition of non-protein groups (carb, lipid, phosphate)
  • modifying amino acids and formation of bonds, e.g. disulfide bridges
  • folding/shortening of proteins
  • modification by cAMP
38
Q

what are homeobox genes

A

a group of genes containing a homeobox

39
Q

what is the homeobox

A

section of DNA 180 base pairs long coding for a part of the protein 60 amino acids long
- is highly conserved in plants, animals and fungi

40
Q

what is the homeodomain

A

part of the protein coded by the homeobox
- binds to DNA and switched genes on and off

41
Q

what type of genes are homeobox genes

A

regulatory genes - switch genes on and off

42
Q

what are hox genes

A

one group of homeobox genes only present in animals
- responsible for the correct positioning of body parts
- found in clusters (4 clusters on different chromosomes in mammals)

43
Q

how do hox genes express

A
  • the order in which genes appear along the chromosome is the order in which the effects are expressed in the organism
44
Q

what is a common feature of body plans

A
  • they are segmented, with segments multiplied over time and specialised to perform different functions
45
Q

what are the examples of symmetry in body shape

A
  • radial, like jellyfish (diploblastic animals with 2 layers of tissue) = only top and bottom, not left or right
  • bilateral = have left side, right side, head and tail
  • asymmetry, like sponges = no lines of symmetry
46
Q

what is apoptosis

A

programmed cell death

47
Q

what are some uses of apoptosis

A
  • removes unwanted cells and tissues
  • remodelling of tissue (release chemicals stimulating mitosis and cell proliferation)
  • hox genes regulate apoptosis and mitosis
48
Q

what is stress and what does it impact

A

condition produced when homeostatic balance within an organisms is upset
- influences the expression of regulatory genes, and can be caused internally or externally
- apoptosis and genes controlling cell cycle can respond to this

49
Q

what are external factors impacting gene expression

A

change in temperature
change in light intensity

50
Q

what are internal factors impacting gene regulation

A

release of hormones
psychological stress

  • drugs can also impact regulatory genes
51
Q

when do factors impacting gene regulation have the most impact

A

during growth and development of an organisms

Biology Module 6 (6 decks)

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