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Biology Paper 2 > Gene expression and DNA technology > Flashcards

Gene expression and DNA technology Flashcards

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1
Q

What is a gene mutation?

A

changes in sequence of nucleotide bases in DNA

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2
Q

What genes control the rate of cell division?

A

Proto-oncgenes

Tumour suppressor genes

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3
Q

What is the function of a Proto-oncogene

A

genes that code for proteins that stimulate cell division

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4
Q

What is the function of Tumour suppressor genes?

A

genes code for proteins that slow cell devision

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5
Q

What can happen if mutations occur in proto-oncogenes and tumour suppressor genes?

A

mutations can lead to rapid uncontrolled cell division (by mitosis) leading to the development of a tumour

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6
Q

How do mutations in proto-oncogenes occur?

A

a mutated version called a oncogene stimulates cells to divide too quickly

resulting in tapid uncontrollable cell division

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7
Q

How do mutations in Tumour suppressor genes occur?

A

a mutation leads to the tumour suppressor protein not being made of being non functional*

results in rapid uncontrollable cell division

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8
Q

What is cancer?

A

a group of diseases caused by alterations in the genes that regulate mitosis and the cell cycle

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9
Q

What is a tumour?

A

masses of dividing cells

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10
Q

What are the two types if tumours

A

Benign

Malignant

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11
Q

Describe a benign tumour

A
  • grow slower than malignant
  • non cancerous, they dont spread to other tissues bc the tumour is enclosed by fibrous tissue
  • cells remain differentiated (specialised)
  • nucleus has a normal appearance
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12
Q

Describe a Malignant Tumour

A
  • grow faster than benign
  • cancerous cells break off and spread to other parts of the body bc tumour isn’t enclosed
  • cells become undifferentiated (not specialised)
  • nucleus is larger and darker
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13
Q

What are stem cells?

A

undifferentiated cells that can divide by mitosis and differentiate into different types of cells

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14
Q

What are Totipotent stem cells?

A

occur for a limited time in early manmalian embryos

can differentiate into any type of cell

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15
Q

What are pluripotent stem cells?

A
  • found in embryos and develop from totipotent stem cells
  • can differentiate into almost any type of cell
  • cant produce cells of embryonic tissue
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16
Q

What ate the two embryonic stem cells

A

Totipotent

Pluripotent

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17
Q

What are multi-potent stem cells?

A

adult stem cells

found in mature aminals

differentiate into few limited types of specialised cells

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18
Q

What are unipotent stem cells?

A

found in mature animals

can only differentiate into one type of cell

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19
Q

What are induced pluripotent stem cells (iPS)?

A

type of pluripotent cell produced from unipotent stem cells

appropriate transcription factors make the unipotent cell pluripotent

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20
Q

What is the function of iPS cells?

A

develop into a wide range of different types of tissue which could be used to treat people with certain diseases

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21
Q

What is the function of a transcription factors?

A

proteins that bring about expressions of some genes and inhibit other genes so that these cells differentiate a particular cell

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22
Q

Describe the role of oestrogen and gene expression

A
  • oestrogen is lipid soluble and diffuses across the cell membrane
  • oestrogen specifically bind to a receptor protein that is part of a transcription factor
  • transcription factor enters nucleus
  • binding change of shape of TF and allows it to bind to promoter sequence of a gene
  • allows RNA polymerase to attach to gene and catalyse transcription
  • mRNA then subscribed then translated into a protein
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23
Q

how can oestrogen lead to cancer?

A

In some tissues oestrogen increases the expressions of genes

so high concentrations can increase uncontrollable cell division

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24
Q

How does Tamoxifen treat some breast cancer?

A

it is converted into endoxifen which is a molecule of a similar structure to oestrogen

It competes with oestrogen for biding to an oestrogen receptor

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25
Q

what is siRNA?

A

short double stranded sections of RNA
Usually 20 to 25 base pairs long

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26
Q

what is the function of siRNA?

A

Regulates gene expression by causing mRNA to be broken down after transcription thus preventing translation

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27
Q

How does siRNA prevent translation?

A
  • double trended RNA is hydrolysed into short molecules
  • RNA becomes single stranded siRNA
  • siRNA binds to an enzyme that hydrolyses mRNA
  • it then binds to a specific molecule of mRNA by complementary base pairing and guides to hydrolytic enzyme to a target molecule of mRNA
  • The enzyme hydrolyses the mRNA this prevents the translation
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28
Q

What is epigenetics?

A

change in gene function without changes in the base sequence DNA

heritable

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29
Q

What causes epigenetics?

A

aspects if the environment
e.g stress diet

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30
Q

What are. two epigenetic changes?

A

increased methylation of DNA

decreased acetylation of associated histones

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31
Q

How does increased methylation occur?

A
  • methyl group attaches to the DNA sequence of a gene
  • attaches to CpG site
  • prevents binding of transcription factors to promoter sequence so gene isn’t expressed
  • thus preventing transcription
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32
Q

How does acetylation increase transcription?

A

histones are more acetylated meaning the chromatin is less condense

so transcription is more likely as genes are more accessible to transcription factors

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33
Q

How does acetylation decrease transcription?

A

histones are less acetylated so the chromatin is more condensed

This inhibits transcription as genes are not accessible to transcription factors

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34
Q

how can epigenetic changes lead to disease?

A

By causing abnormal activation/inhibition of genes

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35
Q

How can cancer develop from hypermethylation?

A

too much methylation of tumour suppressor genes so they are not transcribed

the proteins that slow down cell division are not produces causing rapid cell division

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36
Q

How can Hypomethylation cause cancer?

A

too little methylation of proto-oncogenes so they’re continually transcribed

this increases production of proteins involved in stimulating cell division causing rapid cell division and to development

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37
Q

What are the function of restriction endonucleases?

A

hydrolyse phosphodiester bonds in DNA/RNA producing smaller fragments

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38
Q

Where do restriction enzymes hydrolyse DNA/RNA?

A

at specific base sequences AKA recognition sequences

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39
Q

How are sticky ends made

A

when restriction enzymes hydrolyse DNA at different locations other then the recognition sites

40
Q

How are blunt ends made?

A

When restriction enzymes hydrolyse DNA at the same position in both strands

41
Q

What is the function of sticky ends?

A

enable DNA to be joined or spliced onto a different piece of DNA more easily

because complementary base pairing occurs between sticky ends

42
Q

What is gel electrophoresis?

A

Separates DNA/RNA fragments from

  • small fragments will travel faster/further thru the gel when an electric charge is applied
43
Q

Where do fragments move in gel electrophoresis?

A

Negatively charged DNA fragments move towards positively charged terminals

44
Q

Outline gel electrophoresis

A
  • DNA samples placed in well at top of gel
  • DNA fragments in the each sample separate according to size
  • fragments are then transferred to a nylon membrane then radioactively labelled probes are added
  • nylon membrane is placed on X-ray and position of radioactivity labelled fragments are revealed as dark bands (autoradiography)
45
Q

What are DNA ladders?

A

has DNA fragments of known size and are used to calculate the size of unknown samples

46
Q

What is a polymerase chain reaction?

A

enables multiple copies of identical fragments of DNA/genes to be produced from a small sample

47
Q

outline a polymer chain reaction

A
  • Primers and DNA are mixed and heated at 95°/ 5 minutes (breaks hydrogen bonds s)
  • cool to 55°/2 minutes allows primers to anneal to specific target sequence
  • free DNA nucleotide align to DNA strands by CBP
  • temperature is increased to 72° (optimum for DNA polymerase) enzyme joins nucleotides to form new complementary strand
48
Q

how do you calculate the number of molecules produced in PCR?

A

2^n

n= number of cycles

49
Q

What is a DNA primer?

A

short single standard molecules of DNA

Provide starting sequence for DNA polymerase
- Important because DNA polymerase can’t begin at a single stranded starting point

Prevent original DNA strands joining back together

50
Q

What is a DNA probe?

A

short single standard molecules of DNA that are radioactively/fluorescently labelled

Used to identify/locate known sequences of DNA

51
Q

What is recombinant DNA technology?

A

transfer of fragments of DNA from one organism/species to another

52
Q

What is a transgenic organism?

A

organism that has received transferred DNA

53
Q

how can you obtain a required fragment/gene using reverse transcriptase?

A
  • mRNA uses as a template to produce required chain/fragment of DNA
  • mRNA is mixed with free nucleotides and reverse transcriptase
  • free DNA nucleotides align next to
    complementary bases on mRNA
  • reverse transcription joints, DNA nucleotide together triple produce a fragment/gene
  • DNA strand produced by this is called complementary DNA
  • Double stranded DNA is produced from cDNA using DNA nucleotides and DNA polymerase
  • No introns
54
Q

How can you obtain a fragment using restriction enzymes?

A

required gene/fragment can be removed from the DNA using restriction endonuclease enzymes

-Contains introns

55
Q

How can you produce fragments using a gene machine?

A
  • doesn’t need pre-existing DNA or mRNA as a template
  • amino acid sequence of a protein is used as a template to determine the sequence of DNA nucleotides for a specific gene
  • automated process — required nucleotide sequence is programmed into the gene machine

No introns

56
Q

Why must introns not be present in gene transfers?

A

If the source of the gene is eukaryotic and the recipient is prokaryotic introns can’t be present

57
Q

what are promoter and terminator regions?

A

sections of DNA which must be added to the gene/fragment of DNA for successful transcription of the transferred genes in the recipient cells

58
Q

What is a promoter region?

A

initiate transcription by promoting the binding of RNA polymerase

59
Q

What is a terminator region?

A

marks the end of a gene and triggers release of the mRNA transcribed

60
Q

What does it mean to amplify fragments of DNA?

A

Increase the number by replication

61
Q

what is invivo?

A

copies are made inside the living organism

62
Q

What is invitro?

A

copies are made outside a living organism

Usually by PCR

63
Q

What are the two techniques of amplification?

A

in vivo
In vitro

64
Q

What is a vector used for?

A

Transfers genes

65
Q

What vector is used in bacteria?

A

plasmid

66
Q

What are some other vectors?

A

Viruses and liposomes (phospholipid sack)

67
Q

What is bacteria used for?

A
  • producing a protein code for by a transferred gene
  • clone genes/fragments (invivo cloning)
68
Q

How does bacteria clone gene/fragments?

A

in vivo cloning

the rapid reproduction rate of bacteria allows a transferred gene to be quickly copied so a large amount of gene product can be obtained

69
Q

How is the plasmid used to transfer a fragment/gene?

A

• plasma is caught using the same restriction endonuclease that cut the gene

• plasma DNA and foreign DNA join by base pairing
as they have complementary sticky ends

• ligase is used to form the phosphodiester bonds

• the plasma with the phone DNA is referred to as a recombinant plasmid

70
Q

What is transformation?

A

process in which bacteria take up the recombinant plasmid

This allows these plasma vectors to be added to a culture of bacteria

71
Q

Why may the use of vectors not work?

A
  • cells may not take up the vector
  • Cells may take up the vector with the vector might not contain the gene
    (plasma may have joined back together without the foreign DNA being taken up)
72
Q

What is marker gene?

A

Allows successfully transformed bacteria/eukaryotic cells to be detected and isolated for subsequent culturing

73
Q

How does GFP gene detect bacteria/eukaryotes?

A

GFP gene codes for the production of green fluorescent protein

GFP gene added to the gene being transferred

bacterial/eukaryotes can be identified as they fluorescence when viewed with UV light under a microscope

74
Q

What are some humanitarian benefits of using recombinant DNA technology?

A
  • Reducing famine and malnutrition by developing GM plants/animals which produce high yields and are resistant to disease
  • producing vaccines and drugs
  • Treating genetic diseases by gene therapy
75
Q

what are some drawbacks of using recombinant DNA that come from environmentalists and anti globalisation activists?

A
  • possible transfer of foreign genes to non target organisms
  • An irreversible process with no certainty of economic benefits
  • Ethical considerations with regard to permanently altering the genome of animals
  • Long-term ecological and evolutionary consequences are unknown
76
Q

what is gene therapy?

A

Uses recombinant DNA technology for the treatment of genetic diseases

77
Q

How does gene therapy work?

A

Involves the introduction of functional copies of an allele into an organism which possesses defective alleles of the same gene

78
Q

What are the stages of gene therapy?

A

• identify gene causing the disease

• obtaining and cloning copies of the functional allele

• transferring these functional values into the patient (by use of a vector)

• ensuring that the values reached the target cells and function normally

79
Q

What is DNA sequencing?

A

involves technique to determine the sequence of DNA nucleotide bases (genome)

This allows the sequence of proteins (protein) to be determined

80
Q

what are applications of DNA sequencing?

A

Can identify potential antigens for use vaccines

81
Q

Why can the genome not be translated into proteom in some organisms?

A

these organisms are more complex

presence of non coding DNA and regulatory genes means the genome can’t easily be translated into the proteome

82
Q

What is used to screen people for specific alleles

A

DNA probes and DNA hybridisation

83
Q

What is the procedure for screening?

A

• a DNA probe is made that is complementary to the DNA sequence of the all being investigated

• multiple copies of the DNA probe are made using PCR

• the sample of DNA is obtained from the person/organism being tested

84
Q

Outline screening

A
  • The DNA that’s being tested is fragmented by restriction endonucleases
  • Fragments are separated by gel electrophoresis
  • Fragments are treated and split into single strands
  • Single strands are transferred to nylon membrane and probes are added
  • Membrane is washed remove unattached probes
  • If allele is present labelled DNA probe will bind to a complementary base on one of its strands

presents for as position of probe can be identified by the radioactivity/fluorescence it admits

85
Q

what can patients be screened for?

A
  • Heritable conditions
  • individual drug responses
    people respond differently to particular drugs due to differences in their alleles — this leads to personalised medicine
  • Health risks
86
Q

what is genetic counselling?

A

uses information concerning the presence of identified mutant alleles

87
Q

What is genetic counselling used for?

A
  • understand the probability of people developing a disease
  • Advise parents who may be carriers of a disease causing allele
  • decide the best course of drug treatment for genetic diseases
88
Q

What is a variable number Tandem Repeat

A

many repetitive non-coding sequences of nucleotide bases in a genome

89
Q

what are VNTRs used for?

A

Analysis of these can be used to:

  • determine the relatedness between individuals
  • match the identity of a DNA sample to an individual
90
Q

Outline the procedure of genetic fingerprinting

A
  1. PCR is used to amplify the sample DNA
  2. It’s then cut into fragments using restriction endonucleases
    cut DNA at sites close to, but not within the VTNRs giving a large number of DNA fragments
    (some fragments will be the same length others different)
  3. fragments are separated by gel electro forces.
  4. Fragments are treated using alkali to form single strands
  5. Singles strands are transferred to a nylon membrane
  6. Radioactive probes are added that are complimentary to the repeated sequences.
    Many probes are used and each bind with the VNTRs by DNA hybridisation
  7. Radioactive probes allowed the position of fragments to be identified when the membrane is placed onto an x-ray film (the genetic fingerprint is obtained).
91
Q

How can genetic fingerprints be compared?

A

if fingerprints have bands at the same position on the gel it means they have the same number of nucleotides and repetitive sequences

92
Q

How is genetic fingerprint used in forensic science?

A

By comparing DNA samples from crime scene with DNA of suspects

93
Q

How is genetic fingerprinting used to diagnose?

A

Certain diseases involve unique patterns of several areas and can be identified by fingerprinting

94
Q

How is genetic fingerprinting used to determine genetic relationships?

A

it can determine genetic relationship relationships and genetic variability in a population as more closely related species have more similar VNTRs

95
Q

how is genetic fingerprinting used in animal and plant breeding?

A

Insuring genetic diversity is maintained by screening organisms to prevent inbreeding between closely related individuals

Biology Paper 2 (3 decks)

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