Inheritable Diseases Flashcards
how to investigate a congenital dysfunction?
detailed history of family, pregnancy, examination
find out possible cause.
is it de novo, or syndromic, is it familial or sporadic?
when to use karyotyping vs chromosome microarray
usually do CMA first then if abnormality found, do karyotyping. CMA is faster, but doesn’t tell you about balanced translocations. karyotyping takes 14 days
what is the challenge with whole exome sequencing?
finding out which variants are significant in causing phenotype
what are the rules of inheritance in X linked diseases?
affected males cannot pass it to their sons
carrier moms have 1/4 chance of passing it onto their children
all affected males will pass it onto their daughters
how can women be affected by X linked diseases?
thru random X inactivation
what are the steps in invesigating familial diseases
make the right clinical diagnosis draw the pedigree choose the right genetic test do molecular genetic diagnosis if necessary do cascade genetic test
how many % of x linked diseases happen de novo and how many are inherited?
1/3 are de novo
2/3 are from carrier mothers
(if from father, will know)
if a male child is affected, what are the chances that his grandmother was a carrier?
2/3 chance his mother was carrier
2/3 chance her mother was carrier, therefore 4/9 chance grandma was carrier
if a mother carries an X linked recessive gene has a daughter, what are the chances that the daughter will also be a carrier?
1/2, because the father will pass on healthy copy
what does imprinting mean?
means that depending on maternal or paternal derived copy, the gene can be silenced or unsilenced, thus masking the true status of the gene. even if it was faulty
what do oncogenes generally do?
promote cellular proliferation
when are oncogenes usually switched on and off?
usually on during embryogenesis and off by adulthood.
what happens if the RET oncogene is switched off in fetal stage?
Hirschsprungs disease
what is the APC gene associated with?
FAP
what is the RB1 gene associated with
retinoblastoma
what gene is associated with breast and/or ovarian cancer?
brca1 and brca2
what gene is li fraumeni syndrome associated with?
TP53
what are the two common pathways of colorectal carcinogenesis?
mutator pathway or suppresor pathways
what disease is associated with mutator pathway route of CRC and what disease is associated with the suppresor pathway of CRC?
mutator: Lynch syndrome
suppresor: FAP
describe classical FAP
thousands of adenomas in the colon
how does lynch syndrome compare with FAP?
LSd onset is usually younger, fewer adenomas, malignancy can appear anywhere in the body, commonly colon and endometrium
FAP has more polyps usually in colonc
describe MSI in LSd and how it causes disease
micro satellite instabilities
due to mutations in gene responsible for replication/correcting errors in copying repetitive genes.
this leads to frameshift errors in translation and production of novel peptides, triggering immune response
how to differentiate sporadic CRC from lynch Sd?
amsterdam 3 2 1 criteria
presence of BRAF mutation
and IHC proteins
what is the amsterdam 321 criteria?
3 colorectal tumours in the family
2 generations across
1 diagnosed <50 y/o
why is aspirin given to someone with lynch Sd?
shown to reduce polyp growth
what gene is li fraumeni syndrome associated with
p53
what is a tumour suppresor gene, how many mutations required for disease?
suppresses proliferation, 2 mutations required
what is an oncogene, how many mutations required for disease?
promotes cell proliferation, usually switched off in adulthood. 1 mutation required
what does P53 do?
induce apoptosis
list the 10 hallmarks of cancer
self sufficiency in growth signal insensitivity to anti-growth signals evading apoptosis limitless replicative potential sustained angiogenesis tissue invasion/metastasis deregulated metabolism evading immune system genome instability inflammation
what cancer is the philadelphia translocation associated with?
chronic myeloid leukaemia
what is the difference between germ line mutations and somatic mutations
germ line mutations are present in embryogenesis and are inheritable
somatic mutations occur later in life and are implicated in sporadic cancers
what cancers is alcohol associated with
liver
gut
breast
ovary
how does alcohol cause cancer?
prolonged exposure to acetyldehyde causing oxidative stress
difference between metaplasia and dysplasia
metaplasia is the replacement of one type of cell by another fully specialised cell type
dysplasia is the derangement of cell growth including failure of cells to mature, usually considered pre-cancerous
what are some causes of carcinogenesis?
chemical, physical (radiation), biological (virus/bacteria/parasites), drugs/hormones, nutrition, lifestyle, genetic factors
most common cause of human cancer?
chemicals e.g. smoking
what cancers is smoking associated with? other than lung
oropharynx, osephagus, pancreas, bladder, renal, AML
ovarian and skin cancer are associated with smoking, T or F?
False
how does ionising radiation cause cancer?
causes damage to cellular structures and DNA by displacing electrions and creating ion pairs
what tissue are more prone to ionising radiation?
breast, bone marrow, thyroid
what kind of radiation is UV light?
non-ionising
most common cause of non-ionising radiation cancers?
sun exposure
chronic inflammation has no role in cancers, T or F
F - it plays a central role in biologically caused cancers
what are some viruses that are associated with cancer?
HHV 6 7 and 8 HSV CMV EBV HBV HCV HPV
what cancer are HIV patients more prone to getting?
HHV 8 - kaposi’s sarcoma
what cancer conditions is EBV associated with
hodgkins or burkitts lymphoma
example of bacteria associated with cancer
helicobacter pylori
what is the likelihood of autosomal dominant inheritance in offspring
1/2
eg of triple repeat disorders
huntington’s disease, myotonic dystrophys, fragile x
5 ways to diagnose an autosomal dominant disorder
1) clinically
2) specific gene test
3) gene panel test
4) predictive genetic testing
5) from family history/pedigree