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Flashcards in G9 Deck (15):

give an example of partial monosomy

cri du chat syndrome
characterised by intellectual disabiluty, small head and high pitched cry like a cat


what is chronic myeloid leukaemia due to?

reciprocal translocation between chromosome 9 and 22.


What is fragile x syndrome associated with

expansion of trinucleotide repeat CGG in the 5' UTR of the FMR1 gene.
normal no repeats = 6-60 = no effect
premutation can lead to 55-200 which leads to late onset neurodegeneration in males and 2% risk of premature ovarian failure in females.
full mutation>200 repeats =80% of males being affected by mental retardation and 30% of females


what can cause resistance to HIV infection?

homozygosity for sequence variant in CCR5 (an internal 22bp deletion.)


what does penetrance express?

whether a particular gene can cause a condition, actually does so and at what stage in life, some monogenic conditions are fully penetrant at or before birth.
individual who has genotype but not yet delvetoped is said to be non penentrant.


what is a complex trait?

gene plus environment, no single cause for dieases, low penetrance, epistasis etc.


how many people have monogenic disease CF and DMD

CF = 7000 people
DMD = 3000 people


what are examples of complex diseases and number of people with them

hypertention: 5 mil
cancer 1.5 mil
ischaemic heart diease 1.25 mil
diabetes: 1 mil


What is important to bare in mind when doing genetic testing

dont expect all disease causing sequence variants will be found, not found, doesnt mean not present.
variant may not be disease causing - found doesnt mean responsible


what kinds of genetic screens are there

prenatal screens (high risk)
neonatal screening (treatable inborn errors of metabolism) (reccommended for all new born babies)
prospective parental screens (if both from high risk pops)
pre symptomatic testing for serious late onset disease eg. huntingtons
pre symptomatic testing for genes predisposing to other diseases.


what are the potential harms of genetic screening

psychological distress
risk for employment and insurance
diagnosis of child diagnoses parent without their consent.


Whats special about Jim Watson

Jim watson has over 1 million differences to the HGP reference sequence, but he is 86 and fine.
- shows most DNA changes are silent or of little consequence


what are the steps in forensics?

sample collection
generation of DNA differences
Assessment of differnces
Assignment of probability match or non match of 2 samples
Assess orignal question
did defendent cause the crime?


what are the specific challenges with forensic work?

unknown origin
degradation in collection
probability calculations assuming random mating need to take in social cultural and other considerations


what is the inversion fallacy?

probability the defendent is innocent = P(DNA match given innocent) X P(someone else having a motive) x P(one of these others being in the same city) x p(sample switched with the true criminals DNA due to sampling errors/lab errors) etc etc