Population Genetics Flashcards
what is population geneitcs
study of distrubituion and change in frequence of alleles within populations
what are different factors that could cause change in frequencies of disease or keep constant
genetic - mutation, reproduction, selection
societal - migration, mate selection
enviornmental - geography
Hypotonia, cherry red spot at fovea centralis, earlky age of onset, neural degeneration, death at 5 years is what disease
Tay-sachs disease
what is tay-sachs disease caused by
defecieicny of HexA enzyme
what population of people is incidence rate highest in tay-sachs disease
in ashkenazi jews, french canadians, cajuns
what gene is mutated in tay0sachs disease
HEXA
what enzyme is deficient in tay-sachs disease
Hexosiminidase A (HexA)
What does HexA stand for
Hexosiminidase A, an enzyme
what accumulates in tay-sachs
GM2 gangliosides
what organelle is issues in tay sachs
lysosome
GM2 gangliosides accumulate in what
ganglion cells
what happens to fovea in tay sachs
stays the same color, its red b/c of the vascular choroid layer under it
what happens to macula in tay sachs
it gets lighter, milky or pale gray
when else would you have a cherry red spot besides tay sachs
other lysosomal storage diseases like gaucher
what does HEXA encode
alpha subunit of HexA
what subunits does HEX A have
alpha and beta
what 3 genes are important for the enzyme hexa
HEXA
HEXB
GM2A
If HEXB subunit is mutated what disease
Sandhoff
If GM2A is mutated what is the diseasea
activator deficiency
What is GM2 Gangliosidosis Type 1
tay sachs
what is GM2Gangliosidosis Type 2
Sandhoff
what is GM2Gangliosidosis AB variant
activator deficiency
two alpha subunits from HEXA gene that come together is what enzyme
Hex S
two beta subunits that come together from HEXB gene is what
Hex B
alpha and beta subunit that comes together from HEXA & HEXB is what
Hex A
what is the most common mutation that causes tay-sachs in jewish population
4 bp insertion that results in frameshift
what does the 4 bp insertion result in to cause tay-sachs
frameshift
what does the 4 bp insertion result in to cause tay-sachs
frameshift
what organelle is affected in gaucher disease
lysosome
what population is found at high frequency for gaucher disease
ashkenazi jews
what is MOI for gaucher disease
AR
what gene has mutation in gaucher
GBA
what enzyme does GBA encode
beta glucocerebrosidase
what accumulates in gaucher disease
glucoerebroside
what become lipid filled and enlarged in gaucher disease
macrophages
the total number of allels in a population is ____ the number of indiivduals in a population
twice
what is genotype frequency equation
number of individuals with a defined genotype/total number of individuals in the population
what is allele frequency equation
number of copies of an allele in pop/total number of allels in pop
frequency of allele =
2x homozygote number + 1x heterozygote number/ 2xpopulation
you can only use counting formular when you have what
the genes, you need ro have the alleles to calculate it
what does hardy-weinberg law describe
relationshionship b/w allele and genotype frequencies
p + q = ?
1
homozygous normal AA = ?
p^2
homozygous mutant aa = ?
q^2
heterozygous Aa = ?
2pq
what is the hardy-weinberg formular
P^2 + 2pg + q^2 = 1
What are the 3 assumptions of hardy-weinberg law
large population
random mating
constant gene frequency
if hardy weinberg is true what happens to allele frequencies
they stay constant
is allele frequencies stay constant it is what
at hardy weinberg equilibrium
if you are talking about the incidence rate of a disease being 1 in like 300,000 what is the incidence rate?
q^2
are populations pretty close to being at hardy weinberg equilibrium?
yes pretty close
what is in incidence rate of the disease?
q^2
what is stratified mating
within bigger population are subgroups - can e racial, religious, or cultural - people in the subgroups mate more often than in the larger population
what is affect of stratified mating
if there are mutatnt allele in subpopulation they will stay at higher frequency in subpopulation than they are at in the larger population
what is assortive mating
mate chosen because of a particular trait, like language, intelligence, stature, skin color, athletic ability
what is positive assorative mating
mates chosen b/c they share similar characteristics
what is negative assoritve mating
mates are chosen b/c they have dissimilar characteristics
is positive or negative assoritve mating more common
positive
what are the exceptions to random mating
stratified mating
assortive mating
consanguineous mating
what example is assortative mating resulting in increased genetic diseases
homozygous achondroplasia
genetic deafness
genetic blindness
what is consanguineous mating affect
rare recessive alleles much more likely to become homozygous than expected by random chance
methemoglobinemia does what
hemoglobin doesn’t properly deliver oxygen - blue people!
what is an example of consanguineous mating
blue people of kentucky
what is genetic drift
seen in small populations, allele frequencies fluctuate b/c when people with rare genotypes mate with eachother it will have more signifi ant impact on allele frequency (b/c there are less alleles)
what are exceptions to large population
genetic drift
founder effect
what is the founder effect
start off with big population and some people move somewhere else, over time as the population increases the larger population has same allele frequency as the founding population, and if the founders carried mutant allele its shown greater frequency in the new population
what are examples of founder effect
tay sachs, gaucher: ashkenazics jews
maple syrup urin disease: pennsylvania mennonites
huntington disease: maracaibo venezuela (sailor that had a lot of kids when he visited and he passed on huntington disease)
what is exception to constant allele frequency
gene flow (migration) heterozygote advantage selection against mutant alleles due to loss of fitness
what is gene flow
when a mutation arises it will spread slowly - radially - across its site of origin
what is heterozygote advtange
carriers of disease has increased advantage over both type of homozygous normal genotypes - it provides survival advantage to heterozygotes and a selection for the mutant alleles
what does heterozygote advtange result in
increased frequency of disease alleles in a pop
what are examples of heterozygote advtange
sickle-cell
alpha and beta thalassemia
what is selection against mutant alleles due to loss of fitness
mutant alleles that cuase loss of fitness are only exposed to selection whent heir phenotype is expressed
AD alleles are always expressed and selected against unless there is non-penetrance
so… seletion against mutant alleles will vary depending on how it is expressed
how is x-linked recessie selected against due to loss of fitness
x-linked recessive only expressed and seleted againt in males… so 1/3 of x chromosomes are in males 1/3 of mutatn alleles are selected against
if a male presents with x-linked disorder, what is the chance it was from mother vs. spontaneous mutation
2/3 chance from mother
1/3 chance due to spontaneous mutation
