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A-Level Biology > Mutations and Variation > Flashcards

Mutations and Variation Flashcards

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1
Q

Mutation

A

Change in the sequence of bases in DNA

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2
Q

Ways in which change in sequence can be caused

A

Substitution
Deletion
Insertion

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3
Q

Point mutation

A

Only one nucleotide is affected

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4
Q

Substitution

A

Changes the codon - may still code for the same amino acid (degenerate) ; not changing primary structure

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5
Q

Deletion or insertion

A

Leads to framsehift mutation ; ,over the reading frame of the sequence of bases (non-overlapping) - changes every successive codon from point of mutation

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6
Q

Effects of different mutations

A

No effect
Damaging
Beneficial

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7
Q

No effect

A

No effect on phenotype - proteins still synthesised

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8
Q

Damaging

A

Proteins no longer synthesised or they are non-functional

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9
Q

Beneficial

A

Protein is synthesised that adds a new characteristic - people with a certain mutation are immune to infection from HIV

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10
Q

What increases rate of mutation

A

Mutagens - physical/chemical/biological agent which causes mutations

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11
Q

Examples of mutagens

A

Free radicals can acts as oxidising agents - changing structure of nucleotides/ionising rays
Delaminating agentsbalter bases
Viral DNA may insert itself into a genome

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12
Q

What is a silent mutation?

A

They occur in the non-coding regions of DNA - introns - do not change overall structure of protein

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13
Q

Nonsense mutations

A

Codon becomes a stop codon instead of coding for an amino acid - shortened protein often non functional

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14
Q

Chromosome mutations

A

Alter the whole chromosome - deletion (break off section of chromosome), duplication (sections get duplicated), translocation (section of one chromosome breaks and joins another non-homologous chromosome) and inversion (section is broken off - reversed - and joins back)

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15
Q

Expressing genes only when products are needed

A

Prevents vital resources from being wasted

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16
Q

Gene regulation stages

A

Transcriptional - turned on or off
Post-transcriptional - mRNA modified which regulates translation and types of proteins
Translational - translation can be stopped or started
Post-translational - proteins modified after synthesis which changes their functions

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17
Q

Transcriptional control - heterochromatin

A

Tightly wound DNA causing chromosomes to be visible during cell division

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18
Q

Euchromatin

A

Loosely wound DNA present during interphase

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19
Q

How does hetero/euchromatin affect transcription?

A

Transcription of genes not possible when DNA is tightly wound like with heterochromatin because RNA polymerase cannot access the genes ; genes in euchromatin can be freely transcribed however

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20
Q

How is this example of control?

A

This regulation ensures proteins necessary for cell division are synthesised in time for mitosis - prevents energy intensive process of protein synthesis while cells are still dividing

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21
Q

Histones

A

Positively charged

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22
Q

How does histone modification work?

A

ACETYLATION - REDUCES POSITIVE CHARGE ON HISTONES CAUSING THEM TO COIL LESS TIGHTLY - ALLOWS CERTAIN GENES TO BE TRANSCRIBED
METHYLATION - MAKES HISTONE MORE HYDROPHOBIC SO COIL MORE TIGHTLY - PREVENTS TRANSCRIPTION

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23
Q

Epigenetics

A

Control of gene expression by modification of DNA

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24
Q

Operon

A

Group of genes that are under control of same regulatory mechanisms and are expressed at the same time

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25
Q

How are operons efficient?

A

If certain genes not needed all genes are switched off

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26
Q

If glucose not present….

A

Lactose is metabolised

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27
Q

Lac operon

A

Has 3 genes lacZ, lacY, lacA - structural genes used to code for 3 enzymes (B-galatcisodase etc)

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28
Q

What is sequence of structures with lac operon

A

Regulatory gene (codes for a depressor protein)
Promoter
Operator (what RNA polymerase binds to)

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29
Q

Absence of lactose

A

Regulator gene codes for depressor protein that prevents transcription of structural genes

30
Q

Down regulation

A

Idea of depressor protein binding to operator and preventing RNA polymerase from binding to DNA and beginning transcription

31
Q

Promoter

A

Section of DNA that is the binding site for RNA polymerase

32
Q

When lactose is present

A

Lactose binds to depressor protein causing it to change shape - no longer binds to operator and as a result RNA polymerase can bind to operator allowing enzymes to be synthesised

33
Q

Cyclic AMP?

A

RNA POLYMERASE STILL SLOW RATE OF TRANSCRIPTION that needs to be up regulated to produce the required quantity of enzymes - binding of camp receptor protein RCP (which should be bound to CAMP)

34
Q

Transport of glucose into bacterial cell

A

Decreases camp levels reducing transcription of genes responsible for metabolism of lactose

35
Q

If both glucose and lactose are present

A

Still be glucose that is metabolised - preferred respiratory substrate

36
Q

Caps

A

Pre-mRNA is formed from transcription ; a cap is added to 5’ end and a long chain of adenine nucleotides tail is added to 3’ allowing stabilising of mRNA and preventing degradation in cytoplasm

37
Q

Post transcriptional control mrna

A

Splicing occurs where RNA is cut at introns (non coding dna) and exons are joined together within the nucleus - this nucleotide sequence can be edited by addition/deletion of bases - synthesis of many different proteins from a single mrna molecule

38
Q

Translational control

A

Degradation of mrna - more resistant molecule = longer it will last in cytoplasm so more of protein made
Initiation factors and inhibitory proteins which aid/prevent binding of mrna to ribosomes

39
Q

Protein kinases

A

Catalyse addition of phosphate group to proteins - changes tertiary structure/function of protein - enzymes activated this way

40
Q

Post translational control

A

Non protein groups
Modifying amino acids and formation of bonds (disulfide bridges)
Folding/shortening
Modification by camp

41
Q

Structural vs regulator genes

A

Structural genes encode proteins required for structural/functional use
Regulatory genes encode factors that control expression of structural genes

42
Q

Morphogenesis

A

Regulation of pattern of anatomical development

43
Q

Drosophila

A

Small - easy to keep - have a short life cycle

44
Q

Homeobox genes

A

Group of genes which all contain a homeboys - section of DNA z that is 180 base pairs long coding for a part of the protein 60 amino acids long that is highly conserved in plants animals and fungi

45
Q

What is homeodomain

A

Part of protein that is highly conserved (see homeobox) - binds to DNA and switches other genes on or off thus homeobox = regulatory genes

46
Q

Hox genes

A

Group of homeobox genes that are only present in animals - responsible for correct position of body parts

47
Q

How are hox genes found

A

In gene clusters - mammals have 4 clusters on different chromosomes

48
Q

How have hox genes arisen

A

One notebook gene with accumulated mutations

49
Q

Hox genes along chromosome

A

The order in which they appear along the chromosome is the order in which their effects are expressed in the organism

50
Q

Body plans

A

Cross section through the organism showing fundamental arrangement of tissue layers

51
Q

Diploblastic

A

Two primary tissue layers

52
Q

Tripoblastic

A

Three primary tissue layers

53
Q

Individual vertebrae

A

All developed from segments in the embryo called somites - directed by hox genes to develop in particular way depending on their position in the sequence

54
Q

Radial symmetry

A

No left or right sides only a top and bottom

55
Q

Bilateral symmetry

A

Organisms have both left and right sides and a head and tail rather than top and bottom

56
Q

Asymmetry

A

Sponges - no lines of symmetry

57
Q

Shaping body parts

A

Hox genes regulate both mitosis and apoptosis - role of mitosis is to increase the number of cells leading to growth ; role of apoptosis is to remove unwanted cells and tissues - cells undergoing apoptosis can also release chemical signals which stimulates mitosis and cell proliferation

58
Q

Factors affecting expression of regulatory genes

A

Internal factors - change due to the release of hormones/psychological stress
External factors - a change in temperature or intensity of light

59
Q

Drugs can also affect activity

A

Thalidomide was given to pregnant women to treat morning sickness ; shortened limbs
Prevents formation of stores of capillaries which are necessary for some tumours to grow and develop

60
Q

Beneficial mutation

A

Enhanced function of protein

61
Q

What happens with amino group after Deamination?

A

Converted to ammonia to then be excreted from the body
Can be used as a source for Gluconeogenesis
Enter kerbs cycle as pyruvate

62
Q

Transcriptional control

A

Heterochromatin vs euchromatin
-> acetylayion/phosphorylation
<- methylation

63
Q

Post transcriptional control

A

mRNA splicing (introns and exons) - editing too - many proteins from 1 mRNA
Adenine tail + cap on 5’ prevents degradation in cytoplasm

64
Q

Translational

A

Switching translation on or off - degrade mRNA or inhibitory proteins binding to mRNA prevents binding
Upregulate - PHOSPHORYLATION BY PROTEIN KINASES ACTIVATES INITIATION FACTORS

65
Q

What activates protein kinases

A

Cyclic AMP

66
Q

Post translational control

A

Make it into gylcoprotein - add chains
Protein folding
AMINO ACIDS MODIFIED TO MAKE BONDS
CAMP + CRP - UP REGULATES RNA POLYMERASE/ KINASES

67
Q

Homeobox genes

A

Regulatory genes 180 base pairs long that code for a regulatory protein (part of which is called the homeodomain) that helps determine body plans/development

68
Q

Homeobox genes ARE

A

Highly conserved in plants animals and fungi

69
Q

Function of Homeobox genes

A

Regulate mitosis + apoptosis (hox genes determine this in humans)

70
Q

Hox genes

A

4 clusters - highly conserved

A-Level Biology (37 decks)

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