Polygenic disorders, population genetics and prenatal diagnosis Flashcards
polygenic disorder definition
conditions not controlled by one gene
polygenic traits definition
a whole list of genes and environment that predisposes the individual to get that disease
polygenic inheritance and association to normal distribution
affects are cumaltive, as non are dominant or recessive to one another and thus are additive
recurrence risk definition
the risk that a disease will occur elsewhere in a pedigree, given that at least one member of the pedigree exhibits the disease
what increases the recurrence risk?
the more affected family members
heritability definition
the proportion of the total phenotypic variance of a condition which is caused by additive genetic variance
gene pool definition
the alleles in a population
hardy Weinberg principle use
enable people to predict the incidence of diseased individuals and unaffected carriers if p and q are known
ideal population for hardy weinburg
large, non mating, no new mutations, no selection
real life
non random mating, selection, mutation, migration, small population size
fitness definition
the measure of the ability of an individual to survive and reproduce
genetic drift definition
the effect of reproduction in small gene pools
effects of genetic drift
given time, one allele will become fixed, the other eliminated, new alleles are at greater risk of elimination
genetic flow definition
the movement of alleles from one population to the next
founder effect definition
reduced genetic diversity in a population founded by a small number of individuals
three tests during pregnancy explained
amniocentesis, 16-18 weeks, 0.5-1% miscarriage risk, samples amniotic fluid
chorionic villus sampling, 10-12 weeks, 2% miscarriage risk, samples placenta
NIPT/NIPD- non invasive, detect male foetuses in x-linked contains, looking for SRY
tests prior to pregnancy
PGD- remove 1 cell from each embryo at 8 cell stage, test for mutations
hardy Weinberg equilibrium
the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors
assortative mating definition
persons select individuals that are similar
e.g culture, religion
heterozygote advantage definition
a case where heterozygote genotype has a higher relative fitness than the homozygous dominant or recessive genotypes
explain polymorphism and heterozygotic advantage
polymorphisms can be maintained by selection favouring the heterozygote
explain ethnicity and disease
frequencies in certain populations may be higher due to founder effect
such as tay-sacks in ashkenazi jews
