G9

Question 1

give an example of partial monosomy

Answer 1

cri du chat syndrome

characterised by intellectual disabiluty, small head and high pitched cry like a cat

Question 2

what is chronic myeloid leukaemia due to?

Answer 2

reciprocal translocation between chromosome 9 and 22.

Question 3

What is fragile x syndrome associated with

Answer 3

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

Question 4

what can cause resistance to HIV infection?

Answer 4

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

Question 5

what does penetrance express?

Answer 5

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.

Question 6

what is a complex trait?

Answer 6

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

Question 7

how many people have monogenic disease CF and DMD

Answer 7

CF = 7000 people
DMD = 3000 people

Question 8

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

Answer 8

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

Question 9

What is important to bare in mind when doing genetic testing

Answer 9

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

Question 10

what kinds of genetic screens are there

Answer 10

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.

Question 11

what are the potential harms of genetic screening

Answer 11

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

Question 12

Whats special about Jim Watson

Answer 12

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

Question 13

what are the steps in forensics?

Answer 13

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?

Question 14

what are the specific challenges with forensic work?

Answer 14

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

Question 15

what is the inversion fallacy?

Answer 15

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