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2B > Gene Technology > Flashcards

Gene Technology Flashcards

1
Q

What is cell differentiation?

A

The process by which each cell develops into a specialised structure, suited to the role it will carry out.

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2
Q

Why do differentiated cells differ from one another?

A

Mainly because each cell produces different proteins (the proteins of which are coded for by the gene it expresses).

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3
Q

Give an example of a topipotent cell. Why is it topipotent?

A

A fertilised egg. This is topipotent because it can mature into any body cell.

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4
Q

What happens during cell specialisation that means that cells differentiate?

A

During cell specialisation, only some genes are expressed. Meaning that only part of the DNA in a cell is translated into proteins.

The cell therefore only makes those proteins that it requires to carry out that particular function.

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5
Q

How does a specialised cell conserve energy and resources? Why?

A

A specialised cell is still capable of making all proteins, but they’re not needed so would be wasteful to produce them.

Stimuli (controlling factors) ensure genes and proteins aren’t produced. The way in which they’re prevented from being produced are:

  • preventing transcription (and so the production of mRNA).
  • preventing translation.
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6
Q

What are stem cells?

A

Undifferentiated dividing cells that occur in adult animal tissue and need to be constantly replaced. Self renewal.

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7
Q

What are the different types of stem cells?

A
  • topipotent
  • pluripotent
  • multipotent
  • unipotent
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8
Q

Where do stem cells originate from?

A
  • embryonic stem cells
  • umbilical cord “
  • placental “
  • adult cell “
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9
Q

Where are adult cell stem cells found?

A

Found in the body tissues of the fetus through to the adult.

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10
Q

What kind of cells can embryonic cells produce?

A

They can differentiate into any type of cell in the initial type of development.

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11
Q

What kind of cells can placental stem cells produce?

A

They can develop into specific types of cells.

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12
Q

What kind of cells can adult stem cells produce?

A

They’re specific to a particular type of tissue / organ within which they produce the cells to maintain and repair tissue’s throughout an organism’s life.

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13
Q

Outline topipotent stem cells.

A

Found in the early embryo and can differentiate into any type of cell.

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14
Q

How are pluripotent cells formed?

A

(All body cells are formed from a zygote, so zygotes are topipotent)

As the zygote divides and matures, its cells develop into the slightly more specialised pluripotent stem cells.

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15
Q

Where are pluripotent stem cells found?

A

Embryos

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16
Q

Outline pluripotent stem cells.

A

Found in embryos and can differentiate into almost any type of cell.

(An example: embryonic stem cells)

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17
Q

Where are multipotent stem cells found?

A

Found in adults.

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18
Q

Outline multipotent stem cells.

A

Found in adults. And can differentiate into a limited number of specialised cells.

(Example: adult stem cell, umbilical cord blood stem cell).

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19
Q

Outline unipotent stem cells.

A

Can only differentiate into a single type of cell.

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20
Q

How are unipotent stem cells made?

A

Derived from multipotent stem cells and made in adult tissue.

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21
Q

Where are topipotent stem cells found?

A

The early embryo.

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22
Q

What are induced pluripotent stem cells (iPS)?

A

A pluripotent cell that is produced from a unipotent cell. The unipotent cell may be any type of body cell, of which these body cells are altered in the lab to make them acquire the characteristics of embryonic stem cells (which are a type of pluripotent cell).

Genes that were off are now turned on.

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23
Q

What is the main difference between embryonic cells and iPS cells?

A

iPS cells are capable of self-renewal menacing they can divide indefinitely to provide a limitless supply.

Therefore they could replace embryonic cells and their surrounding ethical issues.

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24
Q

Give examples of what pluripotent cells can be used for.

A

Blood cells - leukaemia
B cells of the pancreas - type 1 diabetes
Heart muscle cells - heart damage (eg from heart attack)
Nerve cells - stroke

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25
Q

Outline some ethical issues of stem cell therapy?

A
  • obtaining embryonic stem cells created by IVF raises ethical issues because the procedure results in the destruction of an embryo which could develop into an embryo if placed in the womb.
  • some people believe that at the moment of fertilisation, an individual is formed who ha the right to life; so many people believe that it’s wrong to destroy embryos.
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26
Q

What are the benefits of stem cell therapy?

A
  • they can save many life (eg many people waiting for organ transplants die before and organ donor becomes available. But stem cells could be used to grow organs).
  • they can improve the quality of life for many people (eg stem cells could be used to replace damaged cells in the eyes of blind people).
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27
Q

What is a mutation?

A

Any change to one or more nucleotide base, or any rearrangement of the bases.

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28
Q

What can cause mutations?

A

Errors during DNA replication.

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29
Q

What are the 6 types of mutation?

A

Substitution, deletion, addition, duplication, inversion, translocation.

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30
Q

What is the mutation: substitution?

A

When one or more bases are swapped for another base.

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31
Q

What is the mutation: deletion?

A

When one or more bases are removed.

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32
Q

What is the mutation: addition?

A

When one or more base is added.

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33
Q

What is the mutation: duplication?

A

One or more bases are repeated.

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34
Q

What is the mutation: inversion?

A

When a sequence of bases is reversed.

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35
Q

What is the mutation: translocation?

A

When a sequence of bases is moved from one location in the genome to another.

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36
Q

What happens if a mutation occurs?

A

Because the order of DNA bases in a genome determines the sequence of amino acids in a polypeptide.
So, if a mutation occurs in a gene, the sequence of amino acids in the polypeptide that it codes for changes.

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37
Q

How could mutations affect enzymes?

A

Polypeptides make up proteins. Therefore a change in the amino acid sequence of the polypeptide may change the 3D shape of the protein, meaning it doesn’t function properly.

Eg a mutation in the polypeptide that makes up an enzyme may change the active site shape, stopping substrates from being able to bind to the active site, so the enzyme cannot catalyse a reaction.

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38
Q

What happens if a fertilised gamete has a mutation?

A

If a gamete contains a mutagen for a genetic disorder is fertilised, the mutation will be present in the new fetus formed (aka hereditary mutations)

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39
Q

Why do not all mutations result in the change in amino acid sequence of a polypeptide?

A

The degenerate nature of the genetic code means that some amino acids are coded for by more than one DNA triplet. Meaning not all types of mutations will result in a change to the amino acid sequence of a polypeptide.

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40
Q

Why do additions, duplications and deletions almost always change the amino acid sequence of a polypeptide?

A

Because these mutations change the number of bases in the DNA code. This causes a frame shift in the flowing base triplets that follow so that a triplet is read in a different way.

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41
Q

How often do mutations occur?

A

They occur spontaneously.

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42
Q

What are the 3 ways in which mutagenic agents increase the rate of mutations?

A

By:

  • acting as a base
  • altering bases
  • changing the structure of DNA
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43
Q

What are the costs vs benefits of mutations?

A
  • they produce genetic diversity; necessary for natural selection and speciation
    However,
  • mutations that occur in body cells rather than gametes disrupt normal cell activities eg cell division
  • they’re almost always harmful
  • produce an organism that’s less well suited to its environment
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44
Q

What does frame shift mean?

A

The reading frame (that consists of three letters of the code) ha been shifted to the left by one letter.

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45
Q

What does RNA polymerase do?

A

It is the enzyme responsible for synthesising mRNA to DNA.

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46
Q

Basically, what happens in transcription?

A

A gene is copied from DNA into mRNA.

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47
Q

All organisms carry the same genes (DNA). So why does the structure and function of different cells vary?

A

Because not all the genes in a cell are expressed (transcribed and used to make a protein).

48
Q

What is a transcription factor?

A

A protein molecule that controls the transcription of genes.

49
Q

In eukaryotes, transcription factors move from the _________ to the _________.

A

From the cytoplasm to the nucleus

50
Q

Outline transcription factors in the transcription of genes.

A
  1. In eukaryotes, TFs move from the cytoplasm to the nucleus.
  2. In the nucleus, they bind to a specific base sequence of DNA.
  3. When it binds, it causes this region to begin the process of transcription.
  4. mRNA is produced and the info it carries is translated into a polypeptide.
  5. When a gene is not being expressed (i.e. it’s switched off), the site on the TF is not active. Therefore cannot cause transcription.
51
Q

Give an example of a molecule that can affect the expression of a gene.

A

Oestrogen.

52
Q

Outline how oestrogen can initiate the transcription of target genes.

A
  1. In the cytoplasm, oestrogen binds with a complementary receptor site on the transcription factor, forming an oestrogen-oestrogen complex.
  2. This causes the oestrogen to change the shape of the DNA binding site on the TF, which can now bind to DNA (it’s activated).
  3. The TF enters the nucleus and binds to specific base sequences on DNA.
  4. The complex acts as an activator, stimulating the transcription of the gene.
53
Q

Define genome.

A

All of the genes in an organism.

54
Q

Define proteome.

A

The full range of proteins that a cell is able to produce.

55
Q

What did the human genome project do?

A

Completed in 2003, the HGP mapped the entire sequence of the human genome for the first time.

56
Q

What does sequencing the genome of simple organisms help to identify?

A

Their proteins.

57
Q

Why is it relatively easy to determine the proteome of bacteria?

A

Because they don’t have much non-coding DNA. Therefore it’s relatively easy to determine their proteome from the DNA sequence of their genome.

58
Q

How can sequencing the genome of simple organisms be useful?

A

It’s relatively easy to determine the proteome from the DNA sequence of a bacteria’s genome because it doesn’t have much non-coding DNA.

Thus proteome can be useful in medical research and development. Eg identifying the protein antigens on the surface of disease causing bacteria and viruses can help in the development of vaccines to prevent the disease.

59
Q

Why is it harder to translate the genome if complex organisms?

A

Because they contain large sections of non-coding DNA.

They also contain regulatory genes which determine when the genes that code for particular proteins should be switched on and off. Making it more difficult to translate their genomes into their proteome, because it’s hard to find the bits that code for the protein amongst the non-coding and regulatory DNA

60
Q

How can scientists now translate whole genomes more quickly?

A

Due to automated, newer, faster techniques (as opposed to labour intensive, expensive and small scale) e.g. pyrosequencing now available.

61
Q

What are the applications of the proteome of a simple organism being discovered?

A

The identification of potential antigens for use in vaccine production.

62
Q

What is recombinant DNA technology?

A

This involves the transfer of fragments of DNA from one organism, or species, to another.

63
Q

In recombinant DNA technology, how can the transferred DNA be used to produce a protein in the cells of the recipient organism?

A

Because the genetic code is universal, as are transcription and translation mechanisms.

64
Q

What are the three ways in which DNA fragments can be produced?

A
  • using reverse transcriptase to convert mRNA -> cDNA
  • using restriction endonuclease enzymes to cut a fragment
  • using a gene machine
65
Q

Outline how using reverse transcriptase can be used to make DNA fragments.

A

mRNA molecules found in cells which are complementary to the target gene can be used as templates to make lots of DNA.

Reverse transcriptase then makes DNA from the RNA template. This produces cDNA. DNA polymerase can then build up the complementary nucleotides on the cDNA template. Producing a double strand.

66
Q

Give an example of the use of reverse transcriptase in the prices of making DNA fragments.

A
  1. B cells from the isles of Langerhans are specialised to produce insult, so also make a lot of mRNA that codes for insulin.
  2. Reverse transcriptase then makes cDNA (single stranded) from insulin mRNA.
  3. The cDNA (single stranded) is isolated by the hydrolysis of the mRNA with an enzyme.
  4. Double stranded DNA is then formed on the template of the cDNA using DNA polymerase. Producing a copy of the human insulin gene.
67
Q

What does a palindromic sequence of nucleotides mean,

A

The sequences consist of antiparallel base pairs (which read the same in opposite directions).

68
Q

What are restriction endonucleases?

A

Enzymes which recognise specific palindromic sequences (recognition sequences) and cut (digest) the DNA at these sites.

69
Q

Why do different restriction endonucleases cut at different recognition sequences?

A

Because the shake of the recognition sequence is complementary to the enzyme’s active site.

70
Q

Outline how restriction endonucleases enzymes work?

A
  1. If recognition sequences are present at either side of the DNA fragment you want, you can use restriction endonucleases to separate it from the rest of the DNA.
  2. The DNA sample is then incubated with the specific specific restriction endonucleases which cuts the DNA fragment out via a hydrolysis reaction.
  3. This can sometimes leave sticky ends. Which can be used to bind the DNA fragment to another ounce of DNA that has sticky ends with complementary sequences.
71
Q

What are sticky ends?

A

Small tails of unpaired bases at each end of the fragment. These can be used to bind the DBA fragment to another piece of DNA that has sticky ends with complementary sequences.

72
Q

In one sentence, what does a gene machine do?

A

Fragments of DNA can be synthesised from scratch without the need for a pre-existing DNA template; instead, a database contains the necessary information to produce the DNA fragment.

73
Q

How does a gene machine work?

A
  1. The sequence needed is produced.
  2. The first nucleotide in the sequence is fixed to some form of support eg a bead.
  3. Nucleotides are added in step by step in the correct order, in a cycle which includes adding protecting groups (these make sure the nucleotides are joined at the right points to prevent unwanted branching).
  4. Oligonucleotides are produced. Once these are complete, they’re broken off from the support and all the protecting groups are removed. The oligonucleotides can then be joined together to make longer DNA fragments.
74
Q

What is an oligonucleotide?

A

A short section of DNA, roughly 20 nucleotides used in the gene machine.

75
Q

What happens once you’ve made DNA fragments?

A

You need to amplify it. So that you have a sufficient quantity.

76
Q

What are the two ways in which DNA fragments can be amplified?

A

In vivo and in vitro.

77
Q

Vector DNA is used in in vivo amplification. What is it?

A

Something that is used to transfer DNA into a cell. They can be plasmids (small molecules of DNA in bacteria) or bacteriophages (viruses that infect bacteria).

78
Q

DNA ligase is used in in vivo amplification. What does it do?

A

It joins the sticky ends of the DNA fragment to the sticky ends of the vector DNA.

79
Q

What is ligation?

A

DNA ligase joins the sticky ends of the DNA fragment to the sticky ends of the vector DNA.

80
Q

In in vivo amplification, what is recombinant DNA?

A

The new combination of bases in the DNA (vector DNA + DNA fragment).

81
Q

In in vivo amplification, what happens if a plasmid vector is used?

A

Host cells have to be persuaded to take in the plasmid vector and its DNA.

82
Q

In in vivo amplification, what happens with a bacteriophage vector?

A

The bacteriophage will infect the host bacterium by injecting its DNA into it. The phage DNA (with the target gene in) will then integrate into the bacterial DNA.

83
Q

In in vivo amplification, what do marker genes do?

A

Marker genes can be used to identify the transformed host cells.

84
Q

In in vivo amplification, how are marker genes used?

A

Marker genes can be inserted into vectors at the same time as the gene to be cloned. Meaning any transformed host cells will contain the gene to be cloned and the marker gene too.

85
Q

In in vivo amplification, what are promoter regions?

A

DNA sequences that tell RNA polymerase when to start producing mRNA.

86
Q

In in vivo amplification, what are terminator regions?

A

DNA sequences that tell RNA polymerase when to stop producing mRNA.

87
Q

In in vivo amplification, are promoter and terminator regions always present in vectors?

A

They may be present or may have to be added along with the fragment.

88
Q

In vitro amplification uses…

A

The polymerase chain reaction (PCR).

89
Q

In a sentence, what happens in in vitro amplification (using the polymerase chain reaction)?

A

Copies of the DNA fragments are made outside of the living organism using the PCR. This can be used to make millions of copies of a fragment of DNA in a few hours.

90
Q

In vitro amplification requires DNA polymerase. What is this?

A

An enzyme capable of joining together tens of thousands of nucleotides in minutes.

91
Q

In vitro amplification requires primers. What are these?

A

Short sequences of nucleotides which have a set of bases complementary to those at one end of the two DNA fragments.

92
Q

In vitro amplification requires thermocyclers. What is this?

A

A computer controlled machine that varies temperatures precisely over a period of time.

93
Q

What is an acquired mutation?

A

Mutations that occur in individual cells after fertilisation.

94
Q

What happens if there is an acquired mutation in a gene that controls cell division?

A

It can cause uncontrolled cell division (by mitosis).

95
Q

What is a tumour?

A

A mass of uncontrolled cells, due to a cell dividing uncontrollably.

96
Q

What are the two types of gene that control cell division?

A

Tumour suppressor genes and proto-oncogenes.

97
Q

How can a mutation in the gene sequence of a tumour surpressor cause a tumour?

A

Normally, tumour suppressor genes slow cell division by producing proteins that stop cells dividing or cause them to self destruct (apoptosis).

Therefore, if a mutation occurs in the TS gene, the protein isn’t produced. So cells divide uncontrollably; resulting in a tumour.

98
Q

What is an oncogene?

A

A mutated proto-oncogene.

99
Q

How can a mutation in the DNA sequence of a proto-oncogene cause a tumour?

A

Normally, PO stimulate cell division by producing proteins that make cells divide.

If a mutation occurs, the gene becomes overactive. This stimulates the cells to divide uncontrollably, resulting in a tumour.

100
Q

What is the difference between malignant and benign tumours?

A

Malignant - metastasise, but benign - localised.

101
Q

Outline a few differences between tumour cells and normal cells.

A
  • tumour cells divide by mitosis more frequently.
  • tumour cells have different antigens on their surface.
  • tumour cells have a larger and darker nucleus.
102
Q

In one sentence, what is methylation?

A

Adding a methyl group (-CH3) onto a molecule.

This is a method of regulating gene expression.

103
Q

How does methylation normally inhibit the transcription of genes?

A
  • preventing the binding of TFs to the DNA.

- attracting proteins that condense the DNA-histone complex making the DNA inaccessible to TF.

104
Q

How can increased methylation cause the growth of tumours?

A

When tumour suppressor genes are hypermethylated, the genes are not transcribed - so the proteins they produce (to slow division) aren’t made.
This means that cells are able to divide uncontrollably by mitosis and tumours can develop.

105
Q

What does the hypomethylation of PO genes do?

A

Causes them to act as oncogenes; increasing the production of the proteins that encourage cell division.
This stimulates cells to divide uncontrollably, which causes the formation of tumours.

106
Q

In a sentence, what is acetylation?

A

The process whereby an acetyl group is transferred to a molecule.

107
Q

How can decreased acetylation switch a gene off?

A
  • decreased acetylation increases the +ve charges on histones, and therefore increases their attraction to the phosphate groups of DNA.
  • the association between DNA and histones is stronger, and the DNA is not accessible to TFs.
  • these TFs can now no longer initiate mRNA production from DNA (the gene is switched off).
108
Q

What is the problem of increased oestrogen?

A

It is thought to increase the risk of developing breast cancer.

109
Q

In what ways can oestrogen contribute to the development of some breast cancers?

A
  • oestrogen can stimulate certain breast cells to divide and replicate. This naturally increases the chance of mutations occurring, and is increases the chance of cells becoming cancerous.
  • the ability to stimulate division could also mean that is cells do become cancerous, their rapid replication could be further assisted by oestrogen, helping tumours to form quickly.
110
Q

What is a tumour suppressor gene?

A

A type of gene that controls cell division, by slowing it down by producing proteins which stop cells dividing and cause them to self destruct (apoptosis).

111
Q

What is the difference between tumour suppressor genes and oncogenes?

A

Oncogenes cause cancer as a result of the activation of proto-oncogenes. Whereas TS genes cause cancer when they are inactivated.

112
Q

What does the hypermethylation of TS genes do?

A
  • in hypermethylation, the TS gene is inactivated, so genes aren’t transcribed so the TS gene is switched off.
  • because TS genes normally slow down the rate of cell division, its inactivation leads to increased cell division and the formation of a tumour.
113
Q

What is the difference between a proto-oncogene and oncogene?

A

An oncogene is just a mutated proto-oncogene (which controls cell division by stimulating cell division, whereas the oncogene stimulates the cells to divide uncontrollably).

114
Q

Outline genetic factors involved in the development of cancer.

A

Some cancers are linked with specific inherited alleles. If you inherit that allele, you’re more likely to get that type of cancer.

115
Q

Outline environmental factors involved in the development of cancer.

A

Ionising radiation, smoking, high fat diet.

116
Q

Define epigenetics.

A

Heritable changes in gene function, without changes to the base sequence of DNA.

2B (26 decks)

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