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Biology > 3.8 Gene expression > Flashcards

3.8 Gene expression Flashcards

1
Q

What 3 chromosomal mutations are there?

A
  • Translocation = copied + inserted on wrong chromosome
  • Duplication = gene copied twice
  • Inversion = gene removed + added backwards
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2
Q

What causes mutations to form?

A
  • Mistakes during DNA replication
  • Mutagenic chemicals
  • High energy, ionising radiation
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3
Q

Name the 5 stem cell types. Explain each one.

A
  1. Totipotent (differentiate to any cell types)
  2. Pluripotent (differentiate to many cell types)
  3. Multipotent (differentiate to some cell types)
  4. Unipotent (differentiate to only one type of cell)
  5. Induced pluripotent (iPS)
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4
Q

Give an example of each of the 4 naturally occuring stem cell types.

A
  1. Totipotent = zygote
  2. Pluripotent = embryonic stem cell
  3. Multipotent = bone marrow
  4. Unipotent = cardiomyogenic cell
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5
Q

Where are stem cells found in humans?

A
  1. Adult stem cells (bone marrow, skin)
  2. Placental stem cells
  3. Umbilical cord blood stem cells
  4. Embryonic stem cell
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6
Q

What are iPS cells, how are they useful?

A

Induced pluripotent stem cells
- Produced from human unipotent stem cells by genetic engineering (transciptional factors)
- Could replace embryonic stem cells (controversial)
- Use in gene therapy, treating disease and research

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7
Q

What is the role of a transcription factor?

A
  • Binds to promoter region of gene
  • Activates RNA polymerase, allowing it run along section of DNA
  • Expresses gene
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8
Q

Describe how oestrogen plays a role in gene expression.

A
  • Oestrogen (lipid based hormone) enters cell by simple diffusion
  • Binds to transcriptional factor in cytoplasm
  • Conformational shape change in transcriptional factor, able to enter nucleus and bind to promoter region on gene
  • Activates RNA polymerase, gene is expressed
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9
Q

Explain why steroid hormones like oestrogen and testosterone can rapidly enter a cell by passing through its cell-surface membrane.

A
  • They are lipid soluble
  • They can diffuse throuh the phospholipid bilayer of the cell membrane
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10
Q

Suggest and explain why testosterone/oestrogen binds to specific transcription factors in the cytoplasm of cells.

A
  • Transcription factor (protein) has a specific tertiary structure
  • This shape is complimentary to oestrogen/testosterone so the two can bind
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11
Q

How can a gene be turned on through the control of transcription?

A

DNA coils less tightly, better access for transcriptional factors and RNA polymerase, genes expressed:

  1. Acetylation of histones - acetyl group added, histone made more -ve so DNA and histones have negative repulsions
  2. Decreased methylation of DNA- methyl group removed from base
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12
Q

How can a gene be turned off through the control of transcription?

A

DNA coils more tightly, less access for transcriptional factors and RNA polymerase, genes not expressed:

  1. Deacetylation of histones- acetyl group removed, histone made more +ve so stronger attraction between -ve DNA and histones
  2. Methylation of DNA- methyl group added to base, attracts proteins that cause deacetylation
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13
Q

What molecule is used in RNA interference?

A

siRNA (small interfering RNA)

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14
Q

How is siRNA produced and how does it control translation?

A
  • Excess mRNA strands form double stranded RNA (dsRNA) form
  • dsRNA is hydrolysed by enzymes into small strands and is split into single strands
  • Forms siRNA-enzyme complex in cytoplasm
  • siRNA binds to mRNA with complimentary base sequence
  • Enzyme bound to siRNA able to cut mRNA, breaking it down so it is unable to bind to ribosomes, gene unable to be translated
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15
Q

What is epigenetics?

A

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

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16
Q

Describe the differences between the two types of tumours.

A
  • Benign has localised symptoms, maligant has systemic symptoms
  • Malignant are cancerous, benign are non-cancerous
  • Malignant grow more rapidly and can form secondary tumours (metastasis)
  • Benign tumours can still cause damage by blockages or growths putting pressure of organs/tissues
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17
Q

What is cancer and how does it form?

A

When tumour cells break away from the primary tumour to form a secondary tumour elsewhere in the body (metastasis).
- Mutation in proto-oncogenes (forming oncogenes), stimulates cell replication
- Mutation in tumour supressor genes, inhibits tumours

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18
Q

Explain why it is important to destroy all the cancer cells in a tumour.

A
  • Cells can metastasise, break off to other parts of the body
  • The remaining cancer cells will divide, forming secondary tumours
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19
Q

How can mutations in proto-oncogenes and tumour supressor genes cause tumours to form?

A
  • If either proto-oncogene mutates it forms oncogenes which stimulate rapid cell division
  • If (both) tumour suppressor genes are switched off tumours are not surpressed and continue to grow
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20
Q

Explain how increased methylation could lead to cancer.

A
  • Increased methylation (on both) tumour supressor genes
  • DNA-histone complex coils more tightly
  • Transcription inhibited as RNA polymerase and transcription factors have decreased access
  • Uncontrolled cell division as tumour suppressor genes are not expressed/are turned off
21
Q

What is the genome and proteome?

A

Genome = all of the genes within an organism
Proteome = all of the proteins coded for by the genome at one time

22
Q

How has the Human Genome Project been used?

A
  • Scientists have been able to see correlations between the presence of certain genes and diseases
  • Application in gene therapy and disease treatment
23
Q

What are the applications of the proteome in science?

A

Identifying potential antigens for use in vaccine production

24
Q

Why is it difficult for scientists to identify the proteome?

A
  • Large amounts of non-coding DNA, hard to identifty proteome from non-coding parts
  • Proteome is larger than genome due to alternative splicing
  • Post-translational modification fo proteins (golgi apparatus)
25
Q

Explain how determining the genome of a virus could allow scientists to develop a vaccine.

A
  • Can identify proteins/sequence proteome
  • Able to identify potential antigens for the vaccine
26
Q

Describe the 3 methods used for DNA fragmentation.

A

Reverse transcriptase
- complimentary DNA (cDNA) produced from isolated mRNA

Restriction endonucleases
- cut at specific recognition sites
- produce blunt/sticky ends (exposed bases)
- DNA ligase forms helix of recombinant DNA (half RNA/DNA)

Gene machine
- artificial, computer

27
Q

Describe how a gene is inserted into a plasmid and how the plasmids are inserted into the bacteria cell.

A
  • Sticky ends are complimentary on RNA and DNA (cut by same restriction endonuclease)
  • Promoter region and terminator region added to gene
  • Heat shock of bacteria cell in calcium chloride solution makes the bacteria cell more permeable so plasmids are able to pass into the bacteria
28
Q

What are the 3 outcomes of transformation?

A
  1. Bacteria transformed
  2. Bacteria not transformed, no plasmid is taken up
  3. Bacteria not transformed, plasmid taken up is not transformed
29
Q

What 3 ways can you identify if a bacteria has been transformed?

A

Insert gene into the following markers:
1. Fluorescent protein
2. Enzymes
3. Antibiotic resistance
Genes not transcribed.

30
Q

Why is antiobiotic resistance a flawed method for identifying a transcribed bacteria?

A
  • Recombinant DNA will make the antibiotic resistance gene non-functional
  • Therefore when testing (adding antibiotic) you will kill the bacteria you require
31
Q

Describe how a scientist can genetically engineer a bacteria to produce an enzyme.

A
  • Cut gene from DNA of a cell using a restriction endonuclease
  • Use same restriction endonuclease enzyme to cut plasmid
  • Produces sticky ends which allow the DNA molecules to join when DNA ligase is added
  • The gene should be inserted into a marker gene (antibiotic resistance)
  • Use heat therapy to increase permeability of bacteria membrane in order to insert plasmid back into the bacterial cell
  • Select bacteria that have been successfully transformed
32
Q

What does PCR stand for and what does it do?

A

polymerase chain reaction
- artificial method of copying small fragments of DNA

33
Q

What 5 components are needed to carry out PCR?

A
  1. Thermocylcer
  2. DNA primers
  3. DNA nucleotides
  4. DNA polymerase
  5. DNA fragment
34
Q

Describe and explain how the polymerase chain reaction is used to amplify a DNA fragment.

A
  • In the thermocycler add the DNA, DNA polymerase, DNA nucleotides and primers
  • Heat to 95°C in order to break the hydrogen bonds between the DNA strands, creating single strands
  • Then decrease temperature to around 50°C to allow primers to bond to the DNA and hydrogen bonds to form between the nucleotides and DNA
  • Then increase temperature to 70°C, allowing the DNA polymerase to join the nuceltides (phosphodiester bond)
35
Q

Describe and explain the change in the number of DNA molecules during PCR.

A
  • Slow increase, then exponential decrease and then increase plateus
  • Only a small number of DNA molecules at the start
  • Exponential increase as it begins to double each time
  • Nucleotide and primer number decreases and runs out
36
Q

What are primers and what are the 2 purposes of them in PCR?

A

Short single-stranded DNA, provide starting sequence for DNA replication

  • Primers stop the two strands of DNA from bonding together again
  • Primers create binding points for DNA polymerase
37
Q

Why does PCR have a low accuracy?

A

Any mistakes that happen during PCR are multiplied quickly

38
Q

What methods are in vivo and in vitro in genome technologies?

A

PCR = in vitro
Transformation of bacteria = in vivo

39
Q

How do you produce a DNA probe?

A
  • Sequence DNA, to find alleles
  • Produce complimentary single strand of DNA fragment and add a marker
  • Use PCR to replicate the probe
40
Q

How do you use a DNA probe to identify the presence of a gene?

A
  • Produce specific DNA probe
  • Extract DNA
  • Seperate strands of DNA using gel electropheresis
  • Treat DNA to form single strands, exposing the bases
  • DNA probe will bind to complimentary gene
  • Use x-ray film or auto-radiography to observe bound DNA probes
41
Q

What are the benefits and negatives of personalised medicine?

A

Benefits:
- Minimise side effects
- Correct and efficient dose
- Reduces risk of disease returning

Negatives:
- Large cost
- Takes a long time and effort

42
Q

What is the purpose of genetic counselling?

A
  • Analyse the risk factors of the results from dna probe
  • Give the patient information to allow them to make an informed decision
43
Q

What are the 4 steps in genetic fingerprinting?

A
  1. Isolation
  2. Fragmentation
  3. Seperation
  4. Comparison
44
Q

What are VNTRs and how do they vary between individuals?

A

Variable number tandem repeats found in introns
1. Number of VNTRs
2. Length of each VNTR

The more closely related two individuals are, the more similar their core sequences will be (VNTRs)

45
Q

Describe fragmentation in genetic fingerprinting.

A

DNA is cut into fragments using restriction endonuclease

46
Q

Describe seperation in genetic fingerprinting.

A

Gel electrophoresis:
- Seperates DNA fragments by mass
- Current passed through agar gel, DNA moves from -ve terminal to +ve terminal
- Smaller DNA fragments travel further than larger fragments

47
Q

How can you use DNA probes in genetic fingerprinting?

A
  • Create single stranded VNTRs by adding alkali
  • Binding of radioactive DNA probe to specific fragments (DNA hybridisation)
  • Wash away unbound DNA probes
  • Add x-ray film (radioactive marker) or UV light (fluorescent marker) to detect fragmentation
48
Q

What does DNA comparison tell you and not tell you?

A
  • Tells you how many VNTRs and the lengths of each
  • Doesn’t tell you anything about a person’s features (comes from introns)
49
Q

What can you use genetic fingerprinting for?

A
  • Identifying criminals
  • Identify microbes
  • Selective breeding of plants and animals
  • Testing genetic variability in a population
  • Paternity tests
  • Medical diagnosis of disease

Biology (10 decks)

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