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Yr 2 - EMS > Gene to Function to Clinic > Flashcards

Gene to Function to Clinic Flashcards

1
Q

What are the breast cancer genes?

A

BRCA1 and BRCA2: The most common cause of hereditary breast cancer is an inherited mutation in the BRCA1 or BRCA2 gene. In normal cells, these genes help make proteins that repair damaged DNA. Mutated versions of these genes can lead to abnormal cell growth, which can lead to cancer.

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2
Q

What % of breast cancers do mutations in BRCA1 and BRCA2 count for?

A

5-10%

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3
Q

The average woman has 12% risk of developing breast cancer (by the time she is 90). How much does having the BRCA1 or BRCA2 mutation increase this risk?

A

Increases risk of breast cancer to 85% (70 years) ALSO Increases risk of developing ovarian cancer from <2% to 55% (BRCA1) and 25% (BRCA2)

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4
Q

What is prophylactic surgery?

A

A form of surgery whose purpose is to minimise or prevent the risk of developing cancer in an organ or gland that has yet to develop cancer and is known to be at high risk of developing cancer. - Removing ovaries after family - Preventative mastectomy

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5
Q

What is effect of removing ovaries on cancer risk?

A

Reduces risk by 85%

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6
Q

What is effect of preventative mastectomy?

A

Reduces risk by 90%

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7
Q

What is presymptomatic screening?

A

Types of testing are used to detect gene mutations associated with disorders that appear after birth, often later in life

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8
Q

What type of diseases are screened for in presymptomatic screening?

A

Late onset disorders: - Huntington’s disease - Retinitis pigmentosa - Breast cancer - Colon cancer

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9
Q

What is ‘penetrance’?

A

Penetrance refers to the proportion of people with a particular genetic change who exhibit signs and symptoms of a genetic disorder. Reduced penetrance –> people with the mutation do not develop features of the disorder

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10
Q

What is non-penetrance?

A

People who have the mutation but don’t show the disease

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11
Q

What is Treacher Collins Syndrome?

A

Craniofacial disorder (genetic) –> characterised by deformities of the ears, eyes, cheekbones, and chin. The degree to which a person is affected may vary from mild to severe (different penetrance)

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12
Q

What is an amniocentesis? When is it performed?

A

Amniocentesis is a procedure in which amniotic fluid is removed from the uterus for testing or treatment. Carried out at around 17 weeks of pregnancy.

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13
Q

What is chorionic villus sampling? When is it performed?

A

A test you may be offered during pregnancy to check if your baby has a health condition or chromosome condition. It involves removing and testing a small sample of cells from the placenta. Carried out at around 11 weeks.

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14
Q

What is NIPD? When is it carried out?

A

New non-invasive method based on next-generation sequencing (NGS) of mothers blood. Can be used to identify whether a foetus has a single gene condition, such as cystic fibrosis or Huntington disease, by testing the foetal DNA in the mother’s blood. Carried out at around 10 weeks.

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15
Q

How does NIPD work?

A
  • Maternal serum contains placental DNA that matches the foetus genome - NGS genome sequencing is performed on the cell-free DNA
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16
Q

What is NIPD also known as?

A

Cell free DNA screening

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17
Q

Benefits of NIPD?

A

Results are far more accurate than current methods (>99% compared to 85% for Downs) and have a much lower false positive rate (0.06% compared to 5.4% for Downs)

18
Q

What does cell free DNA mean?

A

DNA is not in any cells, can just extract from blood sample

19
Q

What are potential dark sides to NIPD?

A

Since test introduced in Iceland, nearly no Down’s Syndrome babies are being born

20
Q

What is preimplantation diagnosis?

A

Refers specifically to when one or both genetic parents has a known genetic abnormality and testing is performed on an embryo to determine if it also carries a genetic abnormality. Would then only implant embryos without mutation.

21
Q

What is preimplantation diagnosis currently used for in UK?

A

HLA typing to match cord blood stem cells for siblings –> ‘saviour sibling’ Also used for single gene disorders Also used for non-disclosure testing (e.g. for Huntington’s disease)

22
Q

What is HLA typing?

A

HLA typing is a kind of genetic test used to identify certain individual variations in a person’s immune system. Critical for identifying who can safely donate bone marrow, cord blood, or an organ to a person who needs a transplant.

23
Q

What is non-disclosure testing?

A

Can perform screening of embryos without knowledge of disease status of parents

24
Q

How is non-disclosure testing used here?

  • Woman has come to clinic
  • Her mum died of Huntington’s
  • She wants to make sure her baby does not get Huntington’s but does not want to know if she carries the gene herself
A
  • Embryos with alleles ‘cc’ are discarded –> chance that one ‘c’ came from the grandma and potentially puts baby at risk of Huntington’s
    • Due to mum being ‘cd’
  • Embryos with ‘cd’ are implanted –> ‘d’ allele must have come from mum therefore ‘c’ must come from dad (no Huntington’s)
25
Q

What is precision therapy?

A

A strategy that integrates molecular information with clinical data to select the best therapeutic intervention.

Lots of different terminology used to describe the same thing

  • genetically-guided therapy
  • personalized medicine
  • stratified medicine
26
Q

What is gene therapy?

A

The use of genetic material (DNA or RNA) as a medicine

  • Introduction of functional genes, in the form of DNA, to replace mutated genes
  • Using gene technology to repair mutated genes, silence overactive genes and to also provide our immune cells with the tools they need to recognise and kill cancer cells and infections
27
Q

What is Leber’s congenital amaurosis (LCA)?

A
  • Rare inherited eye disorder that causes blindness at birth or infancy
  • Accounts for 10-18% of congenital blindness
  • Over 22 genes implicated
  • Recessive inheritance pattern
28
Q

Why is the eye ideal for gene therapy?

A
  • Eye is immune privileged
  • Eye is accessible for subretinal injection
29
Q

What is gene editing?

A

A group of technologies that give scientists the ability to change an organism’s DNA

30
Q

What is pharmacogenetics?

A

Correlation between the effect of drugs and the genetic constitution of patients

31
Q

Why is pharmacogenetics important?

A
  • 100,000 deaths & 2 million serious adverse drug reactions each year in USA
  • 5-7% of hospital admissions due to adverse drug responses
32
Q

What are the cytochrome P450 enzymes? What are they responsible for?

A
  • Multigene family of enzymes found predominantly in the liver
  • Responsible for the metabolic elimination of most drugs currently used (~75%)
  • Also important for converting pro-drugs to their active forms (eg codeine)
33
Q

What is CYP2D6?

A

A highly important polymorphic member of the cytochrome 450 family –> metabolises 25% of drugs

34
Q

What are the potential results of the polymorphism of this enzyme?

A

Results in poor, intermediate, efficient or ultrarapid metabolisers (UMs) of CYP2D6 drugs.

  • 6-10% of Caucasians are non-metabolisers (no active CYP2D6)
  • 7% of Caucasians are ultra-rapid metabolisers (multiple copies of CYP2D6)
35
Q

What problems arise due to polymorphism of CYP2D6?

A

Same drugs will not work on everyone

  • Some won’t be metabolised at all
  • Some will be metabolised too fast
36
Q

How is CYP2D6 involved in tamoxifen metabolism? How can polymorphisms affect this?

A
  • CYP2D6 is the rate limiting step converting tamoxifen to its active metabolite endoxifen
  • Poor metabolizers due to CYP2D6 polymorphisms are associated with worse survival
37
Q

What is preventative medicine?

A

Information about a persons genotype or gene expression profile used to tailor medical care to prevent disease

GP’s will have access to genotyping tests

  • prescribe depending on the results (eg CYP2D6)
  • change lifestyles to fit results
38
Q

Which embryos would be safe to implant?

A

ac, ad

39
Q

What are incidental findings?

A

Previously undiagnosed medical or psychiatric conditions that are discovered unintentionally and are unrelated to the current medical or psychiatric condition which is being treated

40
Q

How are incidental findings dealt with?

A

ACMG (American College of Medical Genetics and Genomics) guidelines –> only report back on actionable results (called secondary findings)

E.g. BRAC1 and long QT syndrome (cardiac defect leading to sudden death)

Untreatable disorders, carrier status etc are not fed back

Yr 2 - EMS (60 decks)

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