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biology factual recall questions > the control of gene expression > Flashcards

the control of gene expression Flashcards

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1
Q

Give six examples of gene mutations

A 
Substitution
Deletion
Addition
Duplication
Inversion
Translocation
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2
Q

What effects do mutagenic agents have on the rate of mutation

A

Increase

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3
Q

What can mutations result in

A

A change in the sequence of amino acids

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4
Q

When mutations only change one codon, why does this sometimes have no effect on the polypeptide coded for

A

DNA code is degenerate

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5
Q

What is a frame shift

A

When a mutation causes all the amino acids after the site of mutation to change

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6
Q

What are base analogues

A

A chemical that can substitute for base in DNA

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7
Q

What are totipotent cells

A

Cells that can specialise into any type of body cell

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8
Q

What are pluripotent cells

A

Cells that specialise into any type of body cell, except placental cells.

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9
Q

What are multipotent/unipotent cells

A

Multipotent Cells can become more than one cell type eg adult stem cells

Unipotent - specialised, can only become one type of cell eg epidermal skin cells

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10
Q

What causes cell specialisation

A

Only part of the DNA is transcribed and translated

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11
Q

how often can pluripotent cells divide

A

unlimited number of times

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12
Q

How are unipotent cells involved in the heart

A

The heart has a supply which are used for repair (Cardiomyocyte)

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13
Q

How are iPS cells created in the lab

A

Scientist take specialised adult cells and “reprogram” them to express transcription factors normally associated with pluripotent stem cells

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14
Q

What is the name of the site at which activators and repressors bind

A

promotor sites

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15
Q

How do Activators effect RNA polymerase binding

A

they make it easier

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16
Q

How do repressors effect RNA polymerase binding

A

they make it more difficult/stop it happening

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17
Q

What type of transcription factor is oestrogen

A

Activator

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18
Q

Give two examples of epigenetic control of gene expression and briefly outline each

A

Increased Methylation - Methyl group attaches to CpG site. This changes DNA structure so the gene is not expressed.
Decreased Acylation - when histone proteins are acylated it is easier for the DNA to be transcribed and the genes to be expressed. Less acylation means the DA is more tightly bound and thus it is harder for the DNA to be transcribed

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19
Q

Can epigenetic changes be passed to offspring

A

Yes

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20
Q

What causes epigenetic changes to DNA

A

Environmental factors

Disease

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21
Q

How does an error in epigenetic control of gene expression link to cancer

A

Abnormal methylation of tumour suppressor genes/protooncogenes prevents them from functioning as they should and allows uncontrolled cell division

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22
Q

Why are epigenetic causes of disease a good target for drugs

A

They are reversible

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23
Q

What is the role of RNAi

A

RNAi prevents m RNA strands from being translated into proteins. It does this by physically blocking translation, before moving the mRNA to a processing body to be degraded or stored

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24
Q

Where in cells does RNAi target the mRNA

A

Cytoplasm

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25
Q

What is a tumour

A

A mass of abnormal cells

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26
Q

What do tumour suppressor genes and protooncogenes both do

A

Tumour suppressor genes produce a tumour suppressor protein that prevents cell division or causes apoptosis.

Protooncogenes produces a protein that enables cells to divide at a controlled rate

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27
Q

if a mutation occurs in the protooncogene, what happens

A

The gene becomes over active and produces lots of proteins that cause uncontrolled cell division

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28
Q

What is a mutated protooncogene called

A

A mutated protooncogene is called an Oncogene

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29
Q

What are the differences between malignant and benign tumours

A

Malignant tumours are cancerous, grow rapidly and invade surrounding tissue. Cells can break off and spread through the body

30
Q

If the tumour suppressor genes become hyper methylated, what happens and how does this link to tumour formation

A

The genes that code for tumour suppressor protein are not transcribed. This means cells division increases

31
Q

Give two theories as to how increased oestrogen levels link to breast cancer

A

It stimulates breast cells to divide. More divisions mean more chance of cancerous cells forming. oestrogen may be able to induce mutations directly in cells

32
Q

How does sequencing the proteome of pathogens help with the formation of vaccines

A

It allows identification of the antigens on the pathogens surface

33
Q

Why is it harder to determine the proteome of humans than of bacteria

A

Humans have introns and regulatory genes

34
Q

What feature of the genetic code, as well as transcription and translation mechanisms means that recombinant DNA technology only requires the transfer of DNA fragments

A

They are universal

35
Q

Give three methods of manufacturing DNA fragments

A

Using reverse transcriptase
Using restriction endonuclease enzymes
using a gene machine

36
Q

What enzymes cut DNA strands and leave sticky ends

A

restriction endonuclease

37
Q

Why is it beneficial for DNA strands to have sticky ends

A

To enable them to be inserted into a complementary section of a vector

38
Q

What is the difference between in Vivo and in vitro gene cloning

A

In vivo cloning is where copies of the DNA fragment are made inside a living organism. This is done by transforming the host cell and then identifying the host cells which have taken up the DNA.

In Vitro uses the Polymerase Chain Reaction to make millions of copies in just a few hours

39
Q

What is a vector

A

Something used to transfer DNA into a cell

40
Q

Give two examples of vectors

A

Plasmids

Bacteriophages

41
Q

Name the enzyme used to stick the DNA fragment to the vector DNA

A

DNA ligase

42
Q

Outline a method for identifying which cells have taken up a vector and its DNA

A

Insert a marker gene for GFP into the vector DNA. Transformed bacteria will possess the green florescent protein and subsequently will glow florescent green

43
Q

Why are promotor and terminator regions added to the DNA of vectors

A

To allow the transformed host cells to produce proteins coded for by the DNA fragment

44
Q

Outline the polymerase chain reaction

A

A mixture is set up containing DNA sample, free nucleotides, primers and DNA polymerase.
heated to 95 degrees C to break the hydrogen bonds between the DNA strands cooled to 50-60 degrees C so primers can bind.
The mix is heated to 72 degrees C so DNA polymerase can line up free nucleotides alongside the template and form new complementary strands
2 new copies of the fragment of DNA are formed and one cycle of PCR is complete

45
Q

Give a benefit of transformed organisms in agriculture

A

Increased crop yield

Crops produce more vitamins/nutrients

46
Q

What is the difference between somatic and germ line gene therapy

A

Germ line is done on sex cells. This means every cell of any offspring produced from these cells will be affected and they will NOT suffer from the disease. This is currently illegal in humans
Somatic is done on adult cells particularly targeting the cells that are most affected by the disorder. Eg cystic fibrosis is damaging to the respiratory system so somatic therapy for CF targets the epithelial cells lining the lungs. This therapy does not affect the sex cells so any offspring could still inherit the disease

47
Q

If a disease is caused by a dominant allele, how would you use recombinant DNA technology to prevent it being expressed

A

Insert “junk” DNA into the dominant allele to prevent it form functioning

48
Q

What are DNA probes

A

Short strands of DNA. They have a specific base sequence that is complementary to the base sequence of part of the target allele so can be used to locate specific alleles of genes eg on chromosomes

49
Q

What is attached to a DNA probes

A

A label

50
Q

List 3 uses of screening with DNA probes

A

Identify inherited conditions
determine how a patient will respond to drugs
Identify health risks

51
Q

What is a VNTR

A

A non-coding base sequence that repeats over and over

52
Q

Why do different VNTRs travel different distances in gel electrophoresis

A

Longer ones are heavier and so travel less distance

53
Q

List two uses of genetic fingerprints

A

Determining who the father of a child is

identifying if a person committed a crime

54
Q

Name the steps involved in In Vivo amplification

A

Copies are made inside a living organism

1) The DNA fragment is inserted into a vector
2) The vector transfers the DNA fragment into Host Cells
3) identifying transformed host cells (only 5% host cells take up vector /dna so important. Markers are antibiotic resistance or flurescence

55
Q

How does In Vitro amplification work

A

Done outside a living organism using the polymerase chain reaction

56
Q

How much dna is made during each PCR cycle

A

Each cycle doubles the amount made ie 1st 2x2=4 dna fragments. 2nd 4 x2 = 8 dna fragments etc

57
Q

If a disease is caused by two mutated recessive alleles how do you alter the genes using gene therapy

A

You add a working dominant allele to make up for them - you supplement the faulty ones

58
Q

Give examples of how DNA probes are used in screening

A

Inherited conditions - Huntington’s disease or cystic fibrosis
Determine how a patient will respond to drugs - breast cancer caused solely by mutation in HER2 protooncogene can be treated with Herceptin
Helps identify health risks - which helps people make informed choices that could reduce the risk of them developing the disease

59
Q

Ethical problems with screening using DNA probes

A

It might lead to discrimination by insurance companies or employers if people are know to have a high risk of developing a condition

60
Q

What is a primer

A

A short piece of DNA that is complementary to the base at the start of the fragment you want

61
Q

How might using recombinant DNA technology benefit people

A

1) Agricultural crops could be produced more efficiently to reduce the risk of famine - drought resistant
2) Transformed crops could be used to produce useful pharmaceutical products eg vaccines available in areas where refrigeration’s (usually needed to store vaccines is not available)
3) medicines could be produced more cheaply and in large quantities and without using animals eg insulin used to come from animals but now human insulin is made using a cloned human insulin gene
4) it has the potential to treat human diseases using gene therapy

62
Q

What are some of the concerns about using recombinant DNA technology in agriculture

A

monoculture - where a farmers only plants one type of crop making them vulnerable to the same disease as all the plants are genetically identical.
Reduction in biodiversity
Possibility of super weeds if transformed crops interbreed with wild plants
Contamination of organic crops by wind blown seeds which would mean organic farmers would not be able to sell their crops

63
Q

What are some of the concerns about using recombinant DNA technology in Industry

A

A few large biotech firms control some forms of genetic engineering. As the use of this technology increases these companies get bigger making it harder for small companies to compete. Anti globalisation protesters think this is bad
Without proper labelling consumers may not have a choice as to whether or not they eat GM food

64
Q

What are some of the concerns about using recombinant DNA technology in medicine

A

Companies who own genetic engineering technologies may limit the use of technologies that could be saving lives
Some people worry that this technology could be used unethically eg making designer babies - currently illegal.

65
Q

What does VNTR stand for

A

Variable number tandem repeats

66
Q

What is a VNTR

A

Base sequences that don’t code for proteins and repeat over and over

67
Q

The number of times a persons VNTR sequences repeats is unique, how does this relate to nucleotides

A

The length of these sequences in nucleotides differs too

68
Q

What is a genetic fingerprint

A

A unique way of identifying someone using patterns in their DNA from VNTR

69
Q

How to make a genetic fingerprint (simple)

A 
Sample of dna taken
PCR used to produce DNA fragments 
Fluorescent tag added 
DNA fragments undergo electrophoresis
DNA fragments are then viewed as bands under UV light
70
Q

Define Electrophoresis

A

Separates DNA Fragments to make a genetic fingerprint

71
Q

Steps of electrophoresis

A

DNA mixture is placed into a well in a slab of gel and covered in a buffer solution that conducts electricity
An electrical current is passed through the gel. DNA fragments are negatively charged so they move towards the positive electrode at the far end of the gel
Small DNA fragments move faster and travel further through the gel so the DNA fragments separate according to size

72
Q

Are DNA fragments positively or negatively charged

A

Negative

biology factual recall questions (9 decks)

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