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The Control of Gene Expression Flashcards

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1
Q

What is substitution when it comes to gene mutations and why may it have no effect on the DNA sequence?

A

When a base is swapped for another base.
No effect on DNA sequence because codon is degenerate.

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2
Q

What is deletion when it comes to a gene mutation?

A

A base is removed, this causes a frame shift to the left.

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3
Q

What is addition when it comes to a gene mutation?

A

When a base is added into the DNA sequence, this causes a frame shift to the right after mutation.

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4
Q

What is duplication when it comes to a gene mutation?

A

When a base is repeated.

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5
Q

What is inversion when it comes to a gene mutation?

A

When a section of bases detach and re attach reversed.

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6
Q

What is translocation?

A

When part of chromosome is removed and moves to the same or another chromosome.

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7
Q

What are mutagenic agents?

A

They increase mutation rate.

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8
Q

How can a mutation affect the DNA sequence?

A
  1. A change in amino acids sequence may affect the tertiary structure of protein due to change of bonds between R groups. No longer complementary.
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9
Q

What are stem cells?

A

Stem cells are unspecialised cells that continually divide and can develop into other types of cells.

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10
Q

What are features of totipotent stem cells?

A
  1. Only present for a limited amount of time.
  2. Produce any type of body cell.
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11
Q

What are features of pluripotent stem cells?

A
  1. Embryonic.
  2. Divide in unlimited numbers.
  3. Develop into most of the body’s cell types.
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12
Q

What are features of multipotent stem cells?

A
  1. Adult cells.
  2. Develop into limited number of cell types.
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13
Q

What are features of unipotent stem cells?

A
  1. Only differentiate into one type of body cell.
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14
Q

How are induced pluripotent stem cells (iPs cells) used in research?

A
  1. Take somatic adult specialised cells and infect them with a modifying virus with genes coding for transcription factors so that the cells become pluripotent.
  2. Transcription factors attach to the promoter region of DNA and stimulate RNA polymerase to stimulate transcription.
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15
Q

What are transcription factors and what do they do?

A

Transcription factors control the transcription of target genes.
They move from the cytoplasm to the nucleus.
They bind to the specific DNA sites near the start of their promoter region of target genes.

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16
Q

What is an activator?

A

They increase the rate of transcription.

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17
Q

What are repressors?

A

They decrease the rate transcription.

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18
Q

How can oestrogen initiate the transcription of target genes?

A
  1. Oestrogen can diffuse through the phospholipid bilayer of membranes into cells.
  2. It binds to the transcription factor (receptor), where it changes shape and releases.
  3. The receptor enters nucleus and binds to promoter region of target gene.
  4. RNA polymerase stimulated to transcribe target gene.
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19
Q

What is RNA interference (RNAi).

A

It can inhibit the translation of mRNA.

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20
Q

What is siRNA?

A

It is double stranded RNA found in the cytoplasm.

21
Q

What is the function of siRNA and describe the process?

A
  1. It associates with some proteins and unwinds to form single strands.
  2. The single strands now binds to target mRNA by complementary base pairing.
  3. The protein associated with the siRNA the cut the mRNA into pieces so it can no longer be translated.
22
Q

Define epigenetics.

A

Heritable changes in gene expression, without change to the base sequence.

23
Q

How does increased methylation inhibit transcription?

A
  1. Methyl groups attaches to DNA.
  2. Changes structure, so RNA polymerase cannot bind.
  3. This may result in the growth of a tumour.
24
Q

How does decreased acetylation of associated histones inhibit transcription?

A
  1. Acetyl groups are removed from the associated histones, which condenses chromatin.
    This means it cannot be transcribed.
25
Q

Why are epigenetic changes good targets for drugs?

A

Epigenetic changes are reversible.

26
Q

What is a tumour?

A

A mass of abnormal cells if a cell divides by mitosis uncontrollably.

27
Q

What is a tumour suppressor gene?

A

They can be inactivated by mutations, or by increased methylation. Mutation or hypermethylation causes uncontrollable cell division.

28
Q

What is proto-oncogene?

A

They stimulate cell division, effect can be increased by mutations, or by decreased methylation, becoming oncogenes.

29
Q

Describe how altered DNA may lead to cancer.

A
  1. DNA altered by mutation.
  2. Mutation changes base sequence of gene controlling cell growth of tumour suppressor gene.
  3. Change protein structure.
  4. Produces proteins that inhibit cell division (mitosis).
  5. Uncontrollable cell division leads to formation of malignant tumour.
30
Q

What is a benign tumour?

A

Not cancerous. They grow slow and are often harmless and do not spread but can cause blockages and put pressure on organs.

31
Q

What are malignant tumours?

A

Grow rapidly and invade and destroy surrounding tissue.
Cells can break off and spread to other parts of the body in the blood or lymph.

32
Q

How may increased oestrogen contribute to some breast cancers?

A
  1. Breast cells may be stimulated to divide.
  2. Introduces mutations directly into DNA of breast cell.
33
Q

Define genome.

A

The entire set of DNA, including all the genes of a cell or organism.

34
Q

Define proteome.

A

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

35
Q

How can genes be copied in terms of recombinant DNA technology?

A
  1. Isolate gene.
  2. Extract mRNA and add reverse transcriptase, which makes complimentary copy of single stranded DNA.
  3. Add DNA polymerase to make it double stranded.
36
Q

How can genes be removed using restriction endonuclease?

A
  1. Restriction endonuclease recognise and cut recognition sequence in DNA.
  2. Active site is complementary to recognition sequence.
  3. This leaves sticky ends, which will easily bind to other DNA fragment using same restriction endonuclease.
37
Q

How can a gene be made in a ‘gene machine’?

A
  1. Design new sequence of desired amino acids of new protein.
  2. Attach the first nucleotide to a bead then add others step by step.
38
Q

What is an advantage using the gene machine?

A

It is faster than the enzyme-catalysed reactions.

39
Q

Describe the method of in-vivo cloning with the use of an antibiotic resistant marker gene.

A
  1. Isolate wanted gene from another organism.
  2. Using restriction endonuclease to get DNA and produce sticky ends.
  3. Use ligase to join wanted gene to plasmid. 5. Add plasmid to bacteria to grow (colonies) then (replica) plate onto medium where the marker gene is expressed. 6. Not killed have antibiotic resistance gene and (probably) the wanted gene.
40
Q

Define promoter region?

A

DNA sequences indicating to RNA polymerase when to start producing mRNA.

41
Q

Define terminator region?

A

DNA sequences indicating to RNA polymerase when to stop producing mRNA.

42
Q

Define primer.

A

Short lengths of single stranded DNA, to mark beginning or end of DNA needed for attachment of enzymes or nucleotides.

43
Q

Describe how PCR is carried out.

A
  1. DNA is heated to 95C and breaks hydrogen bonds, which becomes templates for new complementary strands.
  2. Cooling to 55C causes primers to attach to DNA template strands at complementary base pairing as hydrogen bonds reform.
  3. Raise temperature to 70C, optimum for DNA polymerase, which attaches to primer and adds new complementary bases to template.
44
Q

Define DNA probe.

A

Short strands of DNA that have specific sequence, which is complementary to part of a target allele.

45
Q

What can DNA probes be used for?

A

To locate specific alleles of genes to identify health risks.

46
Q

What are VNTRs?

A

Non-coding sequences of DNA in a genome. They repeat a different number of times.

47
Q

What is electrophoresis?

A

Separates DNA fragments to make a genetic fingerprint.

48
Q

Describe the process of electrophoresis.

A
  1. A fluorescent DNA is added to DNA in order to be viewed under UV light.
  2. DNA fragments undergo electrophoresis.
  3. An electrical current is passed through the well.
  4. DNA fragments are negatively charged so move towards positive electrode.
  5. Smaller fragments move faster and further than longer fragments.
49
Q

Name uses of genetic fingerprinting.

A
  1. Determining genetic relationships.
  2. Determining genetic variability.
  3. Forensic Science.
  4. Medical diagnosis for cancers and genetic disorders.

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