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A-level Biology > CONTOL OF GENE EXPRESSION > Flashcards

CONTOL OF GENE EXPRESSION Flashcards

TOPIC 8

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1
Q

GENE MUTATION

A

change in base sequence of DNA
occurs during DNA replication

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2
Q

MUTANGENIC AGENTS

A

chemical or radiation that
increases mutation rate

.Base analogs: can substitute for base eg. 5-bromouracil can substitute for Thymine, but pairs w/Guanine instead of Alanine
.Altering bases: eg. alkylating agents add an alkyl to Guanine so changing its structure so that it pairs w/Thymine instead of Cytosine
.Altering DNA structure: eg. Ultra Violet radiation can cause adjacent Thymines to pair

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3
Q

ADDITION MUTATION

A

One extra base is added to the DNA sequence
causes all subsequent codons to be altered-frameshift

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4
Q

DELETION MUTATION

A

One base is deleted in the DNA sequence
causes all subsequent codons to be altered-frameshift

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5
Q

SUBSITUTION MUTATION

A

One base in DNA sequence is changed
no frameshift
only one codon changes
may have no impact due to degenerate genetic code

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6
Q

INVERTED MUTATION

A

section of bases detach from DNA sequence and re-join inverted
results in different amino acids being coded for in this region

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7
Q

DUPLICATION MUTATION

A

One base is duplicated at least once in sequence causes frameshift to right

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8
Q

TRANSLOCATION MUTATION

A

section of bases on one chromosome detaches and attaches to different chromosome

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9
Q

FRAMESHIFT

A

change in all the codons after point of mutation each base shifts left or right one position

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10
Q

IMPACT OF GENE MUTATIONS ON PROTEINS

A
  1. DNA base sequence
  2. mRNA codons
  3. amino acid sequence
  4. ionic/H/disulphide bonds
  5. tertiary structure
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11
Q

MUTATIONS HAVING NO EFFECT ON PROTEINS

A

Some mutations, such as substitutions, change only one triplet code in DNA-degenerate nature of genetic code this means that sequence of amino acids will not change

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12
Q

CHANGE IN AMINO ACID SEQUENCE COULD CAUSE

A

.May affect location of ionic/hydrogen/disulphide bond between R groups
.Change tertiary structure of protein
.May create nonfunctional protein

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13
Q

NON-FUNCTIONING PROTIEN

A

Protein w/different primary and tertiary structure- shape is changed it cannot carry out its function + prevent enzyme-substrate complexes from forming

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14
Q

STEM CELLS

A

undifferentiated cells that can continually divide and become specialised

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15
Q

TOTIPOTENT STEM CELLS

A

divide and produce any type of body cell

.Only present for limited time in first few divisions of mammalian embryo
.During development not all stem cell genes are expressed, so some are not transcribed or translated to proteins
.genes that are expressed lead to synthesis of proteins that determine cell structure and function-cell is now specialised and this is irreversible

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16
Q

PLURIPOTENT STEM CELL

A

Embryonic stem cells that can divide in unlimited numbers and develop to most of body’s cell types

can be used to treat human disorders, as they can differentiate to any body cell- get from 4-5 day old embryos that are spare from being used in IVF In vitro fertilisation treatment and rest of embryo is destroyed leads to ethical concerns regarding their use in research and treatment

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17
Q

MULTI-POTENT STEM CELL

A

Adult cells that can develop into limited number of cell types

have an operation to obtain bone marrow cells from donor that can develop to red blood cells or white blood cells

Can be used to replace variety of different cell types but it is limited-Requires donation of stem cells from genetically compatible donor – reduces chance of rejection, but rejection is still possible

Reliance on donors is an issue due to lack of suitable donors
Has less ethical issues as donors are usually consenting adults

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18
Q

UNIPOTENT STEM CELLS

A

Can only differentiate to one type of cell

E.g. Cardiomyocytes are highly specialised heart muscle cells- are very specialised, they cannot regenerate by mitosis themselves- formed from one type of unipotent stem cell that divides and differentiates to cardiomyocyte

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19
Q

IPS BEING USED IN RESEARCH + MEDICINE

A

.Take somatic adult specialised cells, and infect them w/modified virus w/genes coding for transcription factors so that cells become pluripotent
.Transcription factors attach to promoter region of DNA and stimulate RNA polymerase to stimulate transcription
.cells divide and differentiate to desired cells

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20
Q

IPS BEING TRANPLANTED

A

cells modified come from patient themselves- reduces chance of rejection when new cells are transplanted back in

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21
Q

EVALUATING USE OF STEM CELLS IN TREATING HUMAN DISORDER

A

Benefits: All stem cell treatments in medicine provide long term treatment as they continuously divide
Stem cells could be used to grow organs to save lives, or replace eye tissue
Bone marrow stem cells are already being used to treat leukaemia and have been used to cure HIV

Issues: Obtaining embryonic stem cells involves destruction of an embryo
Better to use adult stem cells e.g. iPS which could possibly be made from patient’s own cells-cells continuously dividing increases risk of uncontrollable cell division and production of tumours
nonfunctioning cells must be destroyed e.g. by chemotherapy treatment, before new functioning stem cells are injected – this can be painful and increase chance of infection

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22
Q

GENE EXPRESSION

A

ability of gene to be transcribed to mRNA and translated to polypeptide

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23
Q

PROMOTOR

A

section of DNA before gene where RNA Polymerase binds

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24
Q

TRANSCRIPTION FACTORS

A

proteins which bind to promotor region on DNA they move from cytoplasm to nucleus and stimulate RNA polymerase to produce mRNA + Inhibit binding of RNA polymerase preventing production of mRNA

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25
Q

ACTIVATORS

A

increase rate of transcription eg. Help RNA polymerase bind

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26
Q

REPRESSORS

A

decrease rate of transcription eg. Bind to start of gene and prevent RNA polymerase from binding

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27
Q

OESTROGEN

A

initiate transcription of target genes

small, hydrophobic hormone-means it is lipid soluble and can diffuse through phospholipid bilayers of membranes to all cells
Only target cells contain oestrogen receptor ERα in cytoplasm
ERα is also a transcription factor but is only ‘activated’ when oestrogen binds
When oestrogen binds to ERα oestrogen receptor in cytoplasm, it changes shape
ERα oestrogen receptor can now enter nucleus and bind to promoter region of one of its target genes, stimulating RNA polymerase to transcribe that target gene

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28
Q

MIRNAS

A

formed as hair-pin bends of RNA but processed to single strands about 22 to 26 nucleotides long- single strands become incorporated to protein-based RISC

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29
Q

SIRNAS

A

formed as long double-stranded molecule and then diced to smaller fragments about 21 to 25 base pairs long- One of their strands becomes incorporated to protein-based RISC

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30
Q

HOW RNAI INHIBIT TRANSLATION MRNA

A

1.DNA produces miRNA or siRNA in nucleus
2.RNAi moves from nucleus to cytoplasm
3.RNAi unwinds to become single stranded
4.RNAi binds to protein to form RISC
5.single stranded siRNA or miRNA binds to target mRNA molecule by complementary base pairing
6.prevents mRNA from attaching to ribosome and being translated
7.Enzymes may then hydrolyse mRNA

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31
Q

THERAPUTIC APPPLICATION OF SIRNAS

A

.siRNAs created against viral genetic material will signal for their degradation and stop the virus from using host’s cellular machinery to replicate itself

.siRNAs can be used in cancer treatment by targeting oncogenes that have been expressed or unregulated
reduces number of proteins produced that can lead to cancer or that maintain cancerous growth

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32
Q

EPIGENTICS

A

heritable change in gene function
without changing DNA base sequence
caused by changes in environment
can inhibit transcription

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33
Q

INCREASED METHYLATION OF DNA

A

Methyl groups –CH3 are attached to gene (Could be the result of diet/stress/smoking/food availability)
Hypermethylation of promoter prevents transcription factors from binding
RNA Polymerase is not stimulated- gene is not transcribed, and mRNA is not made + gene is not expressed

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34
Q

DECREASED ACETYLATION ASSOCIATION OF HISTONES

A

Acetyl groups –COCH3 are removed which condenses chromatin-Transcription factors cannot bind to promoter region- RNA Polymerase is not stimulated
gene can’t be transcribed so mRNA is not made + gene is not expressed

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35
Q

WHY ARE EPIGENETIC CHANGES ARE GOOD TARGETS FOR DRUGS

A

drugs can be developed to switch DNA methylation off so can be used to treat cancers cause by increased methylation of tumour suppressor genes

36
Q

TUMOUR SUPPRESSOR GENES

A

group of genes which prevent cell from dividing or triggers apoptosis-programmed cell death

37
Q

INCREASED METHYLATION/DECREASED ACETYLATION IN TUMOUR SUPPRESSOR GENES

A

prevent transcription factors and RNA Polymerase from binding-mRNA cannot be made and therefore protein is not produced-results in cell going into mitosis when it normally would not and therefore causing uncontrollable cell division

38
Q

PROTO-OCONGENES

A

group of genes which trigger cell division
genes which regulate cell cycle are not expressed ‘normally’ then cell can divide uncontrollably leading to tumour

39
Q

DECREASED METHYLATION/INCREASED ACETYLATION IN PROTO-OCONGENES

A

allows transcription factors and RNA Polymerase to bind more readily-More mRNA can be produced, leading to more of protein to be produced and causing uncontrolled cell division

40
Q

OCTOGENE

A

mutated version of proto-oncogene
results in constant initiation of DNA replication and mitotic cell division
causes tumour formation

41
Q

BENIGN TUMPOUR

A

Slow growing
Non-invasive
Do not metastasise (spread) to other parts of body

42
Q

MALIGNANT TUMOUR

A

Fast growing
Invasive
Do metastasise (spread) to other parts of body

43
Q

HOW OESTROGEN INCREASES THE RISK OF BREAST CANCER

A

Oestrogen is steroid hormone it binds to oestrogen receptor site on transcriptional factor
causing change in shape + moves to nucleus so it can bind to promoter of proto-oncogene stimulating RNA Polymerase and causing mRNA to be created which initiates transcription result in uncontrolled cell division

44
Q

THERAPEUTIC APPLICATION OF BREAST CANCER

A

.Prevention: Can screen for specific known cancer-causing mutations eg. BRCA1 for breast cancer- could have mastectomy if mutation is present
.Treatment: Different mutations need treating differently
.Cure: gene therapy to replace inactivated tumour suppressor genes

45
Q

GENEOME

A

entire set of DNA including all genes of cell

46
Q

PROTEOME

A

full number of different proteins that cell is able to produce

47
Q

THERAPEUTIC APPLICATION OF GENEOMES

A

Knowing which gene in genome codes for which protein allows antigen producing alleles to be identified in pathogens- allows scientists to design DNA and mRNA-based vaccines which are faster to engineer than traditional antigen based vaccines

48
Q

SEQUENCING PROJECTS

A

Reading full genome of organisms
provides opportunities to screen DNA to identify potential medical problems

49
Q

GEL ELECTOPHORESIS

A

separate DNA fragments based upon their length and size

50
Q

WHY FRAGMENTS MOVE + SEPARATE

A

1.DNA has a slight negative charge due to phosphate groups so is attracted towards positively charged electrode – so DNA moves
2.gel used in technique has small pores that smaller fragments can move easier through – causes smaller fragments to move further in given time than larger fragments

51
Q

UNIVERSAL GENETIC CODE

A

codon in one species code for same amino acid in another species

52
Q

RECOMBINANT DNA

A

combining different organisms’ DNA
enable scientists to manipulate and alter genes to improve industrial processes and medical treatment

53
Q

REVERSE TRANCRIPTASE TO CREATE DNA FRAGMENT

A

convert mRNA to single stranded complementary DNA

1.Cells that create target protein are isolated from an organism as these will have lots of mRNA in cytoplasm
2.target mRNA is extracted, and reverse transcriptase added
3.Single stranded complementary DNA is created
4.DNA Polymerase is used to create complementary strand to produce double stranded DNA fragments

54
Q

ADVANTAGES + DISADVANTAGES OF REVERSE TRANSCRIPTASE

A

Advantages: lots of DNA fragments can be produced as there will be multiple copies of mRNA at the start
creates DNA fragments that do not have introns

Disadvantages: relatively slow process

55
Q

RESTRICTION ENDONUCLEASE TO CREATE DNA FRAGMENT

A

recognise specific DNA sequences called recognition sites – bind to these sites and break bonds, cutting the gene from rest of DNA
many different restriction enzymes as they are specific to one recognition site- because they are enzymes w/specific tertiary structure, resulting in specifically shaped active site, complementary to recognition sequence

56
Q

ADVANTAGES + DISADVANTAGES OF RESTRICTION ENDONUCLEASE

A

Advantages: Many restriction enzymes naturally cut DNA in way that creates sticky ends: where one strand of DNA is longer than other w/small tail of unpaired bases
sticky ends make it easier to insert desired gene to another organism’s DNA or to vector as they can easily form hydrogen bonds w/complementary base sequences on other pieces of DNA that have been cut w/same restriction enzyme

Disadvantages: creates DNA fragments w/ introns which could not be inserted to prokaryotic organisms
maximum of 2 DNA fragments per genome could be gained
Relatively slow process

57
Q

GENE MACHINE TO CREATE DNA FRAGMENT

A

genetic code -amino acids are required scientists use computers to generate nucleotide sequence rather than an mRNA template to produce gene

58
Q

ADVANTAGES + DISADVANTAGES OF GENE MACHINE

A

Advantage: Faster to use gene machine than all enzyme-catalysed reactions
creates DNA fragments without introns

Disadvantages: potential harm when creating new or more vigorous pests and pathogens

59
Q

PCR

A

1.Denaturation: Heat to 95oC breaks hydrogen bonds to separate DNA strands which become templates for new complimentary strands

2.Annealing: Cooling to 55oC causes primers to attach to DNA template strands at complimentary sequence as hydrogen bonds reform

3.Elongation - Synthesis of new DNA: Raise temperature to 70oC optimum for DNA polymerase which attaches to primer and adds new bases complementary to template

60
Q

WHAT PCR REQUIRES

A

.Target DNA or RNA being amplified

.primers-short sequences of single-stranded DNA that have base sequences complementary to 3’ end of DNA or RNA being copied define region that is to be amplified by identifying to DNA polymerase where to begin building new strands

.DNA polymerase – enzyme used to build new DNA or RNA strand- most commonly used polymerase is Taq polymerase as it does not denature at high temperature involved during first stage of PCR reaction and secondly, its optimum temperature is high enough to prevent annealing of DNA strands that have not been copied yet

.Free nucleotides – used in construction of DNA or RNA strands

.Buffer solution –provide optimum pH for reactions to occur in

61
Q

PCR GRAPH EXPLAINED

A
  1. relatively low amounts of DNA
  2. DNA is doubling
  3. exponential increase larger amount DNA doubling each cycle
  4. ran out of primer + DNA nucleotides
62
Q

TERMINATOR REGION

A

DNA sequences indicating to RNA polymerase when to stop producing mRNA

63
Q

VECTOR

A

DNA molecule used as vehicle to carry DNA fragment eg. plasmids/viruses

64
Q

PALIDROMIC SEQUENCE

A

sequences of bases that read same forwards as they do backwards

65
Q

STICKY ENDS

A

Exposed staggered ends of bases
palindromic base sequences created by restriction endonuclease enzymes

66
Q

DNA LIGASE

A

used to stick DNA fragment to create recombinant DNA

67
Q

STEPS TO PRODUCE PROTEINS

A
  1. promotor + terminator region to modify fragment
  2. plasmid DNA is cut using same restriction enzyme which was used to isolate DNA fragment
    produces sticky ends on plasmid that are complementary to sticky ends of of DNA fragment
    DNA ligase is used to ‘anneal’ donor and vector DNA-DNA is now called recombinant DNA
  3. Vectors are inserted into the target host cells
  4. Marker genes are inserted to vectors at same time as DNA fragment
68
Q

MARKER GENE

A

ensures that only transformed cells form colonies

69
Q

WHAT MARKER GENES CAN CODE FOR

A

.antibiotic resistance
.Fluorescent proteins
.Enzymes which cause colour changes

70
Q

USES OF RECOMBINANT DNA TECHNOLOGY

A

.Genetic engineering of microorganisms, plants and animals
.Inserting gene to egg cell of female or early animal embryo means all cells of offspring will contain gene
.Promotor regions will only be activated in specific cell types so it could be used to control exactly what cells produces protein could mean protein is harvested more easily and avoids damage to organism by avoiding producing protein in wrong cell
.Agricultural crops could be produced to give higher yield, be resistant to pests or be more nutritious.
.Used in industry e.g. cheese making
.Drug production e.g. insulin
.Gene therapy: inserting alleles into cells using vectors e.g. altered viruses, plasmids or liposomes

71
Q

SOMATIC THERAPY

A

alters alleles of body cells e.g. epithelial cells targeted for patients w/cystic fibrosis
alters alleles in sex cells, meaning all offspring cells will be affected

72
Q

GERM LINE THERAPY

A

alters alleles in sex cells, meaning all offspring cells will be affected

73
Q

ISSUES OF USING RECOMBINANT DNA TECHNOLOGY

A

.Monoculture: planting one type of transformed crop – reduced biodiversity
.Transformed crops could interbreed w/wild plants forming e.g. superweeds
.Organic crops could become contaminated by wind-blown seeds and pollen from transformed crops
.Anti-globalisation activists oppose growth of large multi-national companies which may force smaller companies out of business
.Designer babies – currently illegal

74
Q

HUMANITARIANS THINK RECOMBINANT DNA WILL HELP PEOPLE BY

A

.drought – resistant crops could reduce risk of famine
.Transformed crops could be used to make pharmaceutical products e.g. vaccines and medicines more cheaply
.Gene therapy to treat disease

75
Q

DNA PROBES

A

short, single, strands of DNA that have specific sequence which is complementary to part of target allele

76
Q

STEPS OF DNA PROBES

A
  1. DNA sample broken down to smaller fragments
  2. DNA fragments separated by electrophoresis
  3. DNA fragment treated form single strands + DNA probes added
  4. DNA probes allow specific base sequences of DNA to be detected
77
Q

DNA HYBRIDISATION

A

two complementary single-stranded DNA molecules combine through base pairing to form double-stranded DNA molecule

78
Q

THERAPEUTIC APPLICATION OF DNA PROBES

A

.diagnose genetic disorders
.Can also be used to identify health risks e.g. to cancer and determine how patients will respond to drugs and inform personalised drug treatment
.used to inform genetic counselling: advising on treatment, prevention

79
Q

GENETIC FINGERPRINTING

A

distinguishing between individuals based on their unique DNA sequence

80
Q

VNTRS

A

variable number tandem repeats sequences of bases in introns unique to each person + non coding sequences of DNA

81
Q

CREATING A GENETIC FINGERPRINT

A

.sample cells contain DNA is obtained eg. blood
.use PCR make copies if sample of DNA is small
.use restrictive enzymes to hydrolyse DNA targeted to VNTR regions
.use gel electrophoresis to separate DNA fragments by size
.DNA strand transferred to nylon membrane + treated to make single stranded
.DNA probes specific to each targeted VNTR are added + bind to complementary base pairings
.DNA fragments viewed using UV or X ray to produce pattern of bands
.compare size + positions of bands

82
Q

USES OF VNTRS IN PATERNITY TESTS

A

Individuals inherit half of their VNTRs from each parent-means that 50% of an individual’s bands in their fingerprint will match mother’s bands in their fingerprint means that remaining 50% of bands must match biological father

83
Q

PCR OF VNTRS ONLY

A

Instead of copying entirety of DNA, primers complementary to targeted VNTRs are added to sample- means that scientists can amplify specific VNTRs, allowing forensic analysis of tiny tissue samples and partially degraded DNA
multiple VNTR copies are then separated using gel electrophoresis and analysed using gel electrophoresis

84
Q

STR PROFILLING

A

type of VNTR that occurs when short sequence of DNA is repeated many times in row –eg. triplet such as CAG

85
Q

DNA LADDER

A

mixture of DNA fragments of known lengths-pattern it creates can then be compared to unknown fragments to determine their lengths

86
Q

OTHER USES OF GENETIC FINGERPRINTING

A

more closely the pattern of banding matches more closely related two people are

Determining genetic variability within population-more number of repeats vary, greater genetic variability could inform and prevent inbreeding between animals and plants involved in breeding programmes which could lead to genetic disorders

Medical diagnosis of genetic disorders: STR testing is used to diagnose conditions that are predominantly caused by expansions in length of a specific region of genome

A-level Biology (9 decks)

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