Polygenic disorders, population genetics and prenatal diagnosis

Question 1

polygenic disorder definition

Answer 1

conditions not controlled by one gene

Question 2

polygenic traits definition

Answer 2

a whole list of genes and environment that predisposes the individual to get that disease

Question 3

polygenic inheritance and association to normal distribution

Answer 3

affects are cumaltive, as non are dominant or recessive to one another and thus are additive

Question 4

recurrence risk definition

Answer 4

the risk that a disease will occur elsewhere in a pedigree, given that at least one member of the pedigree exhibits the disease

Question 5

what increases the recurrence risk?

Answer 5

the more affected family members

Question 6

heritability definition

Answer 6

the proportion of the total phenotypic variance of a condition which is caused by additive genetic variance

Question 7

gene pool definition

Answer 7

the alleles in a population

Question 8

hardy Weinberg principle use

Answer 8

enable people to predict the incidence of diseased individuals and unaffected carriers if p and q are known

Question 9

ideal population for hardy weinburg

Answer 9

large, non mating, no new mutations, no selection

Question 10

real life

Answer 10

non random mating, selection, mutation, migration, small population size

Question 11

fitness definition

Answer 11

the measure of the ability of an individual to survive and reproduce

Question 12

genetic drift definition

Answer 12

the effect of reproduction in small gene pools

Question 13

effects of genetic drift

Answer 13

given time, one allele will become fixed, the other eliminated, new alleles are at greater risk of elimination

Question 14

genetic flow definition

Answer 14

the movement of alleles from one population to the next

Question 15

founder effect definition

Answer 15

reduced genetic diversity in a population founded by a small number of individuals

Question 16

three tests during pregnancy explained

Answer 16

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

Question 17

tests prior to pregnancy

Answer 17

PGD- remove 1 cell from each embryo at 8 cell stage, test for mutations

Question 18

hardy Weinberg equilibrium

Answer 18

the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors

Question 19

assortative mating definition

Answer 19

persons select individuals that are similar

e.g culture, religion

Question 20

heterozygote advantage definition

Answer 20

a case where heterozygote genotype has a higher relative fitness than the homozygous dominant or recessive genotypes

Question 21

explain polymorphism and heterozygotic advantage

Answer 21

polymorphisms can be maintained by selection favouring the heterozygote

Question 22

explain ethnicity and disease

Answer 22

frequencies in certain populations may be higher due to founder effect

such as tay-sacks in ashkenazi jews