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Biology > 8a (mutations/gene expression) > Flashcards

8a (mutations/gene expression) Flashcards

1
Q

what is a mutation?
what can they be caused by?

A

a change in the DNA base sequence
random errors in DNA replication, rate increased by mutagenic agents

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2
Q

what are the 6 types of mutation?

A

substitution- one or more bases swapped for another
deletion- one or more bases removed
addition- one or more bases added
duplication- one or more bases repeated
inversion- sequence of bases is reversed
translocation- sequence of bases is moved from one location in the genome to another (within chromosome or to a diff chromosome)

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3
Q

what could happen if a mutation occurs in a gene?

A

amino acid seq in polypeptide that it codes for changes
may change tertiary structure of protein so doesnt work anymore
can increase likelihood of certain cancers/ genetic disorders

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4
Q

what is a hereditary mutation?

A

gamete containing mutation for type of cancer or genetic disorder is fertilised, mutation will be present in new foetus

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5
Q

why might a mutation not cause a change in amino acid sequence?

A

the genetic code is degenerate

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6
Q

what is a frameshift mutation?

A

number of bases in DNA code changes so shift occurs in base triplets that follow so triplet code is read in diff way.
occurs in additions, duplications, deletions

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7
Q

what are mutagenic agents
e.g.

A

increase rate of mutations
(they occur anyway spontaneously)
eg UV, ionising radiation, some chemicals, some viruses

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8
Q

what are the ways in which mutagenic agents can increase rate of mutations?

A
  • acting as a base- chemicals called base analogs can substitute for a base during DNA replication, changing base sequence in new DNA
  • altering (/deleting) bases- caused by some chemicals
  • changing structure of DNA- caused by some radiation causes problems in DNA replication
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9
Q

what are stem cells?

A

undifferentiated cells that can become specialised or produced more copies of themself

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10
Q

what is totipotent?
multipotent?
pluripotent?
unipotent?

A

totipotent- can become specialised into any type of body cell- present in embryo for first few divisions
pluripotent- specialise into most cells (not placenta)
multipotent- can become few specialised cells- adult stem cells
unipotent- can become one type of specialised cell eg skin cells

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11
Q

where are stem cells found?

A

embryo (become specialised to form foetus), adult tissue (become specialised to replace other cells)

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12
Q

how do stem cells become specialised?

A

stem cells all contain same genes but not all are expressed
under certain conditions, certain genes are switched on and off
genes that are expressed get transcribed into mRNA which is translated into proteins which modify the cell, they determine cell structure and control cell processes

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13
Q

why do cells tend to stay specialised?

A

changes to cell produced by proteins that cause cell to become specialised
these changes arent reversed

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14
Q

what is a cardiomyocyte?

A

heart muscle cells that make up a lot of the tissue in our hearts

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15
Q

why did people believe we arent able to regenerate our own heart cells?
what does recent research suggest?

A

in mature mammals, its though cardiomyocytes cant divide to replicate themselves- problem if heart become damaged

hearts do have some regenerative capabilities, old/ damaged cardiomyocytes replaced by new ones derived from small supply of unipotent stem cells in heart.
some think this constantly occurs but dk how fast. some think its really slow and its possible some arent replaced in someones life. some think its really fast and each is replaced multiple times in a life

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16
Q

what are acquired mutations?

A

mutations that occur in individual cells after fertilisation

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17
Q

what are tumour suppressor genes?
what happens if a mutation occurs in them?

A

slow cell division by producing proteins that stop cells dividing/ cause them to self-destruct (apoptosis)

gene will become inactivated. protein it codes for wont be produced and cells will divide uncontrollably

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18
Q

what are proto-oncogenes?
what happens if a mutation occurs in them?
what is a mutated proto-oncogene called?

A

stimulate cell division by producing proteins that make cells divide

gene can become over-active and stimulate cells to divide uncontrollably resulting in a tumour

oncogene

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19
Q

what are malignant tumours?

A

cancers
grow rapidly and invade and destroy surrounding tissue
break off and spread through lymph/blood

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20
Q

what are benign tumours?

A

not cancerous
grow slower than malignant and are covered by fibrous tissue that stops it invading other tissues
often harmless but can cause blockages
can become malignant

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21
Q

how do tumour cells differ from other cells?

A
  • larger, darker nucleus, maybe multiple
  • irregular shape
  • dont produce all proteins needed to function correctly
  • diff antigens on their surface
  • dont respond to growth regulating processes
  • divide more frequently
22
Q

what is abnormal methylation?

A

methylation of DNA is important in regulating gene expression but only in normal amounts
hypermethylation- too much
hypomethylation- too little
can lead to cancer

23
Q

why does increased exposure to oestrogen increase breast cancer risk?

A
  • oestrogen can stimulate certain breast cells to divide and replicate, more divisions increases chance of mutations
  • oestrogens ability to stimulate cell division means if cells become cancerous, rapid replication is assisted by oestrogen
  • oestrogen is able to introduce mutations directly into DNA of certain breast cells
24
Q

risk factors for cancer

A
  • genetic- inherited alleles can make you more likely to get a specific type of cancer eg BRCA1 gene can increase risk of breast cancer
  • environmental- exposure to radiation, lifestyle choices
25
Q

ways of preventing cancer

A

if a specific cancer-causing mutation is known, you can screen for it
knowing about the increased risk means preventative steps can be taken
more sensitive tests can be developed which can lead to earlier and more accurate diagnosis

26
Q

treatments/ cures for cancer

A

knowing how specific mutations cause cancer means drugs can be developed (page 211- examples)
some mutations require more aggressive treatment so understanding it can help produce best treatment plan
gene therapy- faulty alleles replaced by working versions of those alleles

27
Q

what are bone marrow transplants?

A

replacing faulty bone marrow in patients that produce abnormal blood cells (bone marrow contains stem cells that can specialise into any type of blood cell)

28
Q

what could stem cells be used to treat in the future?

A

spinal cord injuries- replace damaged nerve tissue
heart disease/ damage caused by heart attacks
bladder conditions- grow new bladders to be implanted
respiratory diseases
organ transplants

29
Q

what are the sources of stem cells?

A
  • adult stem cells- from body tissue eg bone marrow, simple operation, painful, not as flexible
  • embryonic stem cells- 4-5 day old embryos from ivf, pluripotent
  • induced pluripotent stem cells (iPS cells)
30
Q

what are induced pluripotent stem cells?
how can they be made?

A

‘reprogramming’ specialised adult body cells to become pluripotent
adult cells made to express a series of transcription factors normally associated w pluripotent stem cells so they express genes associated w pluripotency

can introduce transcription factors to adult cells by infecting them w specially-modified virus which has genes coding for the transcription factors . virus infects cell and passes these genes on

31
Q

ethical considerations of embryonic stem cells

A

embryos are destroyed- could have become a foetus
can artificially make egg cells divide wo sperm- may be more ethical as cells couldnt survive/ produce a foetus

32
Q

why are iPS cells a good option?

A

obtained from adult tissue so less ethical considerations
can be made from patients own cells- less likely to be rejected

33
Q

benefits of stem cell therapy

A
  • save lives eg grow organ for people waiting for transplant
  • make stem cells genetically identical to patients cells- wont reject
  • improve quality of life eg replace damaged cells in blind people
34
Q

what are transcription factors?

A

protein molecules that control the transcription of genes

35
Q

role of transcription factors

A

move from cytoplasm to nucleus where they bind to promotor region of DNA and control expression by controlling transcription

36
Q

what are the 2 types of transcription factor?

A

activators- increase rate of transcription (help RNA polymerase bind)
repressors- decrease rate of transcription (bind to promotor region so RNA polymerase cant)

37
Q

how does oestrogen effect gene expression?

A

binds to transcription factor (oestrogen receptor) forming an oestrogen-oestrogen receptor complex which moves (oestrogen changes its shape allowing it to move into nucleus) into the nucleus and binds to a promotor region

38
Q

what is RNAi (RNA interference)?

A

where small, double stranded RNA molecules stop mRNA from target genes being translated into proteins
similar occurs in prokaryotes

39
Q

describe RNAi

A
  • mRNA transcribed and moves from nucleus- cytoplasm
  • in cytoplasm, double stranded siRNA associates w several proteins and unwinds
  • one of the resulting strands of siRNA is selected- other is degraded
  • single strand siRNA then binds to target mRNA due to complimentary base sequences
  • proteins associated w siRNA cut mRNA into fragments so it cant be translated
  • fragments then move into processing body to be degraded
40
Q

what happens in RNAi in plants?

A
  • same as with siRNA but miRNA is used instead
  • miRNA isnt usually fully complimentary to mRNA so it is less specific than siRNA and can target multiple mRNA molecules
  • instead of miRNA cutting mRNA up, it physically blocks translation of target mRNA, mRNA is removed and taken to a processing body to be stored or degraded
41
Q

how does epigenetic control of gene expression work?

A

attachment/ removal of chemical groups (epigenetic markers) to or from DNA or histone proteins
epigenetic markers dont alter base sequence but alter how easy it is for DNA to be transcribed

42
Q

can epigenetic changes be inherited?

A

most epigenetic markers are removed between generations but some escape removal process and are passed to offspring so expression of some genes can be affected by environmental factors that affected parents

43
Q

what is increased methylation of DNA?
where is the methyl group added?

A

methyl group attached to DNA at CpG site (C and G next to each other)
increased methylation changes DNA structure so transcriptional machinery cant interact w gene so it isnt expressed

44
Q

what is decreased acetylation of histones?
what is the enzyme involved

A
  • acetyl groups removed- chromatin (DNA wrapped around histones) becomes highly condensed and genes cant be transcribed because transcriptional machinery cant access them
  • histone deacetylase
45
Q

development of diseases

A

examples on pages 225-226

46
Q

how can you treat diseases caused by epigenetics?

A

epigenetic changes are reversible so drugs can be used to counteract the changes
however, epigenetic changes take place in lots of cells so drugs need to be as specific as possible to avoid damaging normal cells

47
Q

increased/ decreased acetylation/ methylation of DNA/ histones
which way round?

A

increased methylation of DNA
decreased acetylation of histones

48
Q

definition of epigenetics

A

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

49
Q

what is the epigenome?

A

all of the chemical modifications to all histone proteins and DNA in an organism

50
Q

why do menopausal women have a higher risk of breast cancer despite no longer menstruating?

A

after menopause, more oestrogen is produced from the cells of breast tissues

Biology (20 decks)

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