Flashcards in Estimating Risk of Inherited Genetic Disease Deck (19):
the relative ability of organisms to survive and pass on genes
How can alleles affect fitness?
-Neutral allele: not at all in most cases
Deleterious allele: sometimes decrease
Advantageous allele: rarely increase
the frequency of alleles in the whole population affects the health of the population
Why do relative frequencies remain constant?
Dominant conditions/alleles do not become more common at the expense of recessive ones
What assumptions underlie HWE?
-mutation can be ignores
-migration is negligible= no gene flow
-mating is random
-no selective pressure
-population size is large
-allele frequencies are equal in the sexes
What can lead to new gene frequency in a hybrid population?
introduction of new alleles as a result of migration or intermarriage
What increases the proportion of new alleles?
What does non-random mating lead to?
an increase in mutant alleles, thereby increasing proportion of affected homozygotes
choosing of partners due to shared characteristics
marriage between close blood relatives
a gradual process by which biological traits become either more or less common in a populaion
Describe negative selection
-reduces reproductive fitness
-decreases the prevalence of traits
-leads to gradual reduction of mutant allele
Describe positive selection
-increases reproductive fitness
-increases the prevalence of adaptive traits
What can be seen in small populations?
genetic drift which causes a founder effect
ransom fluctuation of one allele transmitted to high proportion of offspring by chance
the reduction in genetic variation that results when a small subset of a large population is used to establish a new colony
Describe genetic drift.
-mutations are widespread and neutral
-statistical drift of gene frequencies due to chance or random events rather than natural selection in the formation of successive generations
How can the founder effect be seen in the Amish of Pennsylvania?
Ellis-van Crevald syndrome