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Biology- topic 8 > Mutations and control of gene expression > Flashcards

Mutations and control of gene expression Flashcards

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1
Q

What is a gene mutation?

A

a change in the base sequence of DNA

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2
Q

When do gene mutations happen?

A

during DNA replication

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3
Q

What types of gene mutation are there?

A

addition, deletion, substitution, inversion, duplication, translocation

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4
Q

What is a mutagenic agent and give 2 examples?`

A

chemical or radiation that increases the rate of mutation - xrays/benzene deriviatives

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5
Q

What happens during addition mutation?

A

one extra base is added, causes frameshift

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6
Q

What happens during a deletion mutation?

A

one base is deleted, causes frameshift

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7
Q

What happens during a substitution mutation?

A

one base is changed/swapped, doesn’t cause frameshift

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8
Q

Why may a substitution mutation not have an impact?

A

genetic code is degenerate

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9
Q

What is frameshift?

A

a change in all the codons after the point of mutation. can be to the left or right

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10
Q

What happens during an inversion mutation?

A

a section of bases detach from the DNA sequence and rejoin inverted, results in different amino acids being coded for

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11
Q

What happens during a duplication mutation?

A

one base is duplicated at least once, causing frameshift to the right

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12
Q

What happens during a translocation mutation?

A

a section of bases on one chromosome detached and attaches to a different chromosome

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13
Q

What is a non-functioning protein?

A

a protein with a different primary and hence different tertiary structure. the shape is changed so it can no longer carry out it’s function

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14
Q

What is a tumour?

A

a mass of cells as a result of uncontrolled cell division, can be benign or malignant

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15
Q

What is a benign tumour?

A

non-cancerous, grows at a slower rate, surrounded by a membrane so don’t spread/metastasise

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16
Q

What is a malignant tumour?

A

cancerous tumour, grows rapidly, can grow projections and hence metastasise, can develop own blood supply

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17
Q

What is cancer?

A

malignant tumours that form due to uncontrolled cell division

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18
Q

What is metastasis?

A

when cancer cells break off from the tumour, spreading to form secondary tumours in different tissues/organs

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19
Q

What are tumour suppressor genes?

A

genes that produce proteins to slow down cell division and cause cell death is DNA copying errors are detected

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20
Q

What is epigenetics?

A

the heritable change in gene function without changing the DNA sequence. caused by changes in the environment - change in phenotype without changing genotype

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21
Q

What is hypermethylation?

A

an increased number of methyl groups attached to a gene, resulting in the gene becoming deactivated

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22
Q

What is the methylation of DNA and how does it inhibit transcription?

A

methyl groups attach to the cytosine base on DNA, which prevents transcriptional factors from binding by making the DNA-histone complex more tightly bound

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23
Q

How can oestrogen increase the risk of breast cancer?

A

oestrogen binds to a receptor site on a transcriptional factor, causing a change in shape so it can bind to the DNA to initiate transcription which can result in uncontrolled cell division, causing cancer

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24
Q

What is a stem cell?

A

undifferentiated cells that can continually divide and become specialised

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25
Q

Why are cells specialised?

A

to save energy - if all genes turned on in all cells the production of the proteins would waste lots of energy

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26
Q

What is a totipotent stem cell?

A

are found in early mammalian embryos, can differentiate into any type of body cell

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27
Q

What is a pluripotent stem cell?

A

found in embryos and can differentiate into nearly any type of body cell

28
Q

What are pluripotent cells used for?

A

in research to help treat genetic disorders - ethical debates as embryo used is destroyed

29
Q

What is a multipotent stem cell?

A

found in mature mammals in bone marrow, can differentiate into a limited number of cells

30
Q

What is a unipotent stem cell?

A

found in mature mammals, can only differentiate into one type of cell

31
Q

What is an oncogene?

A

a mutated version of a proto-oncogene, resulting in the constant initiation of DNA replication and mitosis, causing a tumour

32
Q

Where can you find stem cells?

A

umbilical cord blood, placenta - multipotent stem cells
bone marrow - adult stem cells

33
Q

How do you obtain stem cells from IVF?

A

you can use spare embryos from IVF that aren’t implanted - remove stem cells from inner blastocyst

34
Q

What is an induced pluripotent stem cell?

A

produced from adult somatic cells using protein transcriptional factors

35
Q

What is therapeutic cloning?

A

-producing genetically identical cells
-nucleus of an ovum is removed and replaced with the nucleus of a cell from a patient, the cell is then delivered a small electric shock to start it dividing, then can be removed and cultured to produce genetically identical tissues for the patient

36
Q

Why is it better to use embryonic stem cells instead of adult stem cells?

A

although they don’t have ethical controversies, they are harder to extract and are not pluripotent so are limited

37
Q

What is a transcriptional factor?

A

proteins that can bind to different base sequences on DNA that initiate transcription of genes

38
Q

What is RNA interference?

A

the inhibition of the translation of mRNA, mRNA gets destroyed so it cannot be translated

39
Q

How is RNAi used in medicine?

A

can be used to silence harmful genes

40
Q

What is siRNA and what does it do?

A

small interfering RNA, cleaves mRNA molecules to prevent translation

41
Q

How do cells become specialised?

A

by turning on/off particular genes so only certain proteins are produced

42
Q

How does oestrogen regulate transcription?

A

-oestrogen is a lipid soluble molecule, and therefore diffuses easily through the phospholipid bilayer cell membrane
-once inside the cytoplasm of the cell, oestrogen binds with a site on a receptor molecule of the transcriptional factor, as they are complementary
-by binding with the site, the oestrogen activates it by changing the shape of the DNA binding site on the transcription factor to become complementary to the DNA
-the transcriptional factor can now enter the nucleus through a nuclear pore and bind to specific base sequences on DNA at the promoter region
-the combination of the transcription factor with DNA stimulates transcription of the gene by allowing RNA polymerase to bind

43
Q

Describe siRNA

A

small, double stranded RNA molecules, used by protein complexes to break mRNA down

44
Q

Name two key features of stem cells?

A

-can differentiate into specialised cells
-can self replicate indefinitely

45
Q

How does siRNA interfere with gene expression?

A

the enzyme dicer splits double stranded RNA into smaller pieces, then one strand forms a complex (RISC) with protein, the other is destroyed, the siRNA-protein complex binds to mRNA where it then cuts/cleaves it, leaving the mRNA strand to disintegrate, preventing translation and hence proteinsynthesis

46
Q

What factors can affect epigenetics?

A

drugs, diet, stress, exercise, aging

47
Q

How does epigenetic control work?

A

works through the attachment or removal of chemical groups to or from DNA or histones

48
Q

Where does methylation occur?

A

DNA, to the cytosine bases

49
Q

What affect does increased methylation of DNA have?

A

-inhibits the transcription of genes
-prevents the binding of transcriptional factors to DNA, by attracting proteins that condense the DNA-histone complex, making the DNA inaccessible to transcriptional factors

50
Q

Where does acetylation occur?

A

histones

51
Q

What affect does decreased acetylation of histones have?

A

-inhibits transcription
-increases the positive charges on histones and hence increases their attraction to the phosphate groups in DNA, so there is a stronger association between DNA and histones, so the DNA is not accessible to transcription factors

52
Q

Where does the acetyl group come from?

A

the group donating the acetyl group is acetylcoenzyme A (involved in link reaction)

53
Q

Are epigenetic changes permanent?

A

no

54
Q

Can epigenetic changes be inherited?

A

yes if they occur in the germ cells

55
Q

Why is epigenetics important in cancer research?

A

changes in tumour suppressor genes or proto-oncogenes can cause cancer

56
Q

Evaluate the use of epigenetics in treating disease?

A

epigenetic changes are easier to treat than DNA sequence mutation as drugs can counteract the epigenetic changes that caused the disease by inhibiting certain enzymes involved histone acetylation or DNA methylation - but need to be very specific

57
Q

How can epigenetic changes cause cancer?

A

DNA in promoter regions do not tend to have methylation, but in cancerous cells, sometimes the DNA there can become highly methylated, inhibiting transcription, leading to some protective genes being switched off leading to cancer

58
Q

How may epigenetics be used to diagnose cancer?

A

identify acetylation and methylation relative to normal levels

59
Q

How is SiRNA able to bind to mRNA?

A

SiRNA is only complementary to part of the base sequence of mRNA but it is enough to enable the protein-complex to bind with and destroy the target mRNA

60
Q

How is SiRNA produced?

A

dicer cleavage of long double stranded RNA

61
Q

What is the benefit of SiRNA not being completely double stranded?

A

they contain overhangs of approximately two nucleotides at each end which allows siRNAs to be recognised by a protein complex

62
Q

What is a proto-oncogene?

A

stimulates cell division

63
Q

What is a tumour suppressor gene?

A

slows/inhibits cell division

64
Q

What can happen if there is a mutation in a proto-oncogene?

A

if a point mutation occurs, it can form an oncogene which stimulates excessive cell division leading to the formation of a tumour

65
Q

What can happen if there is a mutation in a tumour suppressor gene?

A

if a point mutation occurs, it can cause the gene to become inactivated which allows the rate of cell division to increase unregulated

66
Q

What is the difference between malignant and benign tumours?

A

malignant - rapid growth, tends to spread and form secondary tumours, can grow finger-like projections into surrounding tissue, more likely to reoccur
benign - slow growth, doesn’t usually spread, cells stick together as a primary tumour, very rare if reoccurs

Biology- topic 8 (2 decks)

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