liveonearth (liveonearth) wrote,

Genetics test: notes from review

27 multiple guess, a single best answer, one on population genetics
5 short answer
one longer question: draw a pedigree, 10-12 people
a few more questions, extra credit, requiring creativity, one on population genetics
not much math, should be able to do in head
remember sample question #4, that one is good tester for how you will do
do sample questions, they're harder than the test
no need to know which xsm a gene is on other than autosomal vs sex xsm
know top 3-4 dz for each inheritance type
if not told much about a person you must make real world assumptions
for all my notes from the class see these posts:

autosomal dominant p53-54
diseases we should know something about
huntington's, neurofibromatosis, osteogenesis imperfecta
mostly structural dz
every affected person has affected parent

autosomal recessive
tend to be metabolic dz
CF on xsm 6, hypopigmentation, PKU
PKU untxd-->full blown dz variable relative to exposures, txd-->normal individual

multiple genes and multiple environmental risk factors
empirical risk table
adolescent idiopathic scoliosis, diabetes mellitus
neural tube defects, pyloric stenosis, cleft lip/palate, club foot
does not present with clean inheritance pattern
closer relation, more severe cases = more likely to have it
*in the absence of models use emp risk tables, if none of those use square root of pop incidence
threshhold trait = 10 genes cause it, if you have more than x you have the dz, x = threshhold
pyloric stenosis threshhold is different in males and females

sex linked
x-linked recessive
arguably metabolic dzs
hemophilia, colorblindness
odds of affected female quite low

p58 familial hypertrophic cardiomyopathy
example of reduced penetrance, given in percentages
single mutation, dominant with reduced pen
occasional skipped generation in family tree


translocation downs syndrome p22
indistinguishable from trisomy 21 which is 95% of the cases
risk of affected child for carrier is quite high
theoretical risk 33% except lower because many abort

PKU p65
aut rec
odds of mating with another near zero so assume zero
carrier 1/50

tay sachs
you and partner both had sib who died of it
parents are obligate carriers
can assume parents didn't have it because affected die very young
thus aut recessive
lysomsomal storage dz-->severe mental retardation
child of two carrier parents has 2/3 chance of being carrier
so chance of you and partner having affected child = 2/3 x 2/3 x 1/4 = 4/36 = 1/9

CF p68
imagine pop incidence is 1/25
normal with CF sib mates with pop
so 2/3 x 1/25 x 1/4 = 2/300 = 1/150

given pop incidence if 1/1600
q = 1/40
2q = 1/20
plug that in for the frequency in prev q was 1/25

p177 q16

ionizing radiation: x rays, fallout, fission, cosmic rays
chemicals: polycyclic aromatic hydrocarbons

Barr bodies
23rd pair is sex xsms
all humans need same amount of x xsm so female needs to shut one down
calico cats

p93 q3
lesh neihan synd
looked it up on omim and it's x linked recessive
2nd child 1/4 risk

xsm 9 and 15 transloc = ??
other transloc that causes dz = ??

q4 p75
aut dom
can be new mutation 1/4000
achondroplastic dwarfism is another that has new mutation rate worth considering
reduced penetrance is key to question

top of p77
male with alcaptonuria mates with pop female, prob of affected child?
aut recessive
assume female is normal -->probably homozygous normal
odds of affected child near zero
if told carrier frequency then you can calculate actual odds
given 1/150 odds, then 1/2 x 1/150 = 1/300 odds of affected child

all these genetic dzs are uncommon

CF 1/2500 ish
Tags: genetics, nd4

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