9/8 Immune disease Flashcards
what are the molecular consequences of mutations (3 types)
- gain of funciton (novel protein product , or over expression or inappropriate isxpression) 2. loss of function (recessive disorders, haploinsufficiency or half othe normal amount of gene product causes disease) 3. dominant negative mutations (product of the altered allele interfered with the normal allele)
what is a gain of function mutaiton
new abnormal protien
what is a loss of funciton mutation
loss of any protien from that allele
what is dominant negative mutations?
the produced allele blocks the normal function of the normal allele
what causes mutation?
- Ionizing Radiation 2. Mutagenic chemicals (base analogues, intercalating agents)
How does radiation cause mutaion
ionizing makes double stranded DNA breaks and base substitiustions; Non-ioniznig formation of pyrimidine dimers
mutagenic chemicals how work?
alkylating agents (potent mutagens) or sacchrine (weak mutagen)
how do we avoid many of our mutations?
DNA repair catches about 99.9% of the mutations. this involves several dozen different enzymes.
Xeroderma pigmentosum
dry skin and extra pigmentation; this is a problem with DNA repair, and can’t repair the damage from the sun. 1000 times more likely to get cancer
what does UV do to the DNA? and how is it repaired?
Thymine dimer is created and causes kink in the DNA; this is repaired by DNA excission repair. This involves seven different genes and mutation in any of them will give xeroderma pigmentosum.
what is the normal mutation rate?
from 10 to the neg four to ten to the neg six
what will affect the mutaiton rate?
the position of the gene or the age of the organism.
what is a mutation hot spot?
a location that is more likely to mutate for example a cytosine to thyosine mutation.
How would an older father affect mutations?
single gene mutations increase with paternal age, with each additional year of age there are about 2 more mutations.
why don’t we see increased mutation in female eggs with age?
the female makes all of the oocytes as an embryo. for males we make the sperm after puberty every two weeks or so. at least 3/4 of mutations are transmitted by males. (800 rounds of reproduction vs. 23ish)
what type of mutationis most likely to result in the complete loss of a protein product?
nonsense mutation
what is gene frequency
the rate at wich a specific genotype appears in the population.
how do we calc. the total genotype frequencies?
the number with the genotype/the total number in the population.
how do we find the gene frequency of a specific allele
multiply the homozygotes by 2 add the number of heterozygotes and then divide by the population doubled!
what is purpose of the hardy weinberg equilibrium
est. the genotype frequencies from gene frequencies and vice-versa
what if we have a f(A) =p=.9 and f(a)=q=0.1 what is the probability of getting a heterzygote or either homozygote?
multiply the frequencies together, so the homozygotes are p squared and q squared, and the heterozygotes are the product of each probability. therefore: .81, .09, .09, and .01 for the respective probabilities. the total heterozygote of course would be 2pq.
how can we predict the prevelence of a carrier based on the prevalence of occurance?
take the squareroot of the rate of the disease (this will be f(a)) then find the f(A) by doing 1-f(a). then do the 2pq equation and find the carrier frequency!
how can you identify autosomal dominant disease?
everyone that has the allele will be phenotyplicaly express the disease. We don’t skip generations. It is common in both male and female (therefore not sex linked). male to male transmission (would rule out the x-linked inheritence) recurrence risk for typical mating is 50%
how could we identify x-linked inheritence
won’t see it passed from male to male!
what if there is no family history of a autosomal dominant disease?
There may be a new mutation in the sperm or egg (or the milk man effect).
what if we see a mutation that is autosomal dominant and occurs repeatedly without a family history?
germline mosaicism. This is when they have the gene for the condition but not in most of their line.
what is germline mosaicism?
cells to the ova and spermatozoa are a mixture of two or more genetically different cell lines.
what are the characteristics of Achondroplasia
disproporionate reduced stature. chadracteristic facial features. lordosis. macrocephaly. caused by gain of function mutation in fibroblast growth factor receptor 3 gene. (FGFR3)
what are some treatments of achondroplasia?
gene therapy through the addition of a ‘decoy receptor’, and surgery.
what happens to a Loss-of-Function at the FGFR3 gene?
very, very tall individuals! so opposite of achondroplasia
