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