Uworld Bio- Genetics and
Evolution (esidahi) complete with
verified solutions(latest updated
version already graded A+)
Genetic drift = chance event - answer Genetic drift
- due to random genetic changes that are not related to
natural selection
- (eg, sampling error, chance event).
- Although all populations are affected by genetic drift, its
effects are more significant in
--> smaller populations because they have a reduced
gene pool.
The smaller gene pool cannot buffer random (good or bad)
variations in allele frequencies that occur due to chance
events.
In other words, the probability of a beneficial allele being
removed by genetic drift increases for populations whose
genetic diversity is low.
Similarly, drift increases the probability of a deleterious
allele becoming fixed within the population.
Bottlenecks = Not by chance - answer Bottlenecks
- is the drastic reduction in population size that occurs in
response to some sudden and uncontrollable disaster
,- due to environmental events (eg, flood, famine, human-
induced catastrophe) or human action (human-induced
catastrophe)
- greatly reduce the genetic diversity of a population.
Consequently, a smaller population has a reduced ability
to buffer the negative impacts of random changes in allele
frequencies (genetic drift) that may result in extinction.
Natural selection - answer Natural selection
- is an evolutionary mechanism by which only beneficial
alleles are selected for while unfavorable traits are
selected against. These selected changes alter the
population's allele frequencies, which improves the
species' fitness.
Consequently, these populations have an improved
probability for survival rather than an increased
probability for extinction.
Gene flow, - answer Gene flow,
- due to migration,
- increases genetic diversity by introducing new alleles to
the gene pool.
Therefore, small populations with low genetic diversity are
more likely to benefit from gene flow and therefore are
less likely to go extinct.
, Random mating - answer Random mating
- increases a population's genetic diversity because of the
inherent variations that arise during meiosis
(recombination) and sexual reproduction (fusion of
gametes).
Therefore, the variations or changes to the allele
frequencies due to random mating will primarily be
beneficial to a population as a whole.
- answer Increase population
- Gene flow
- Random mating
- Natural selection
Decrease population
- genetic drift (can cause extinction in small pop)
- bottleneck effect - decreases diversity
Major Histocompatibility Complex (MHC) - answer MHC
alleles
- encode surface receptors on all nucleated cells that play
a role in the activation of the adaptive immune system.
Typically, increased MHC variation
- enhances an organism's ability to combat a variety of
infections and diseases.
- As a result, it is associated with increased fitness
Evolution (esidahi) complete with
verified solutions(latest updated
version already graded A+)
Genetic drift = chance event - answer Genetic drift
- due to random genetic changes that are not related to
natural selection
- (eg, sampling error, chance event).
- Although all populations are affected by genetic drift, its
effects are more significant in
--> smaller populations because they have a reduced
gene pool.
The smaller gene pool cannot buffer random (good or bad)
variations in allele frequencies that occur due to chance
events.
In other words, the probability of a beneficial allele being
removed by genetic drift increases for populations whose
genetic diversity is low.
Similarly, drift increases the probability of a deleterious
allele becoming fixed within the population.
Bottlenecks = Not by chance - answer Bottlenecks
- is the drastic reduction in population size that occurs in
response to some sudden and uncontrollable disaster
,- due to environmental events (eg, flood, famine, human-
induced catastrophe) or human action (human-induced
catastrophe)
- greatly reduce the genetic diversity of a population.
Consequently, a smaller population has a reduced ability
to buffer the negative impacts of random changes in allele
frequencies (genetic drift) that may result in extinction.
Natural selection - answer Natural selection
- is an evolutionary mechanism by which only beneficial
alleles are selected for while unfavorable traits are
selected against. These selected changes alter the
population's allele frequencies, which improves the
species' fitness.
Consequently, these populations have an improved
probability for survival rather than an increased
probability for extinction.
Gene flow, - answer Gene flow,
- due to migration,
- increases genetic diversity by introducing new alleles to
the gene pool.
Therefore, small populations with low genetic diversity are
more likely to benefit from gene flow and therefore are
less likely to go extinct.
, Random mating - answer Random mating
- increases a population's genetic diversity because of the
inherent variations that arise during meiosis
(recombination) and sexual reproduction (fusion of
gametes).
Therefore, the variations or changes to the allele
frequencies due to random mating will primarily be
beneficial to a population as a whole.
- answer Increase population
- Gene flow
- Random mating
- Natural selection
Decrease population
- genetic drift (can cause extinction in small pop)
- bottleneck effect - decreases diversity
Major Histocompatibility Complex (MHC) - answer MHC
alleles
- encode surface receptors on all nucleated cells that play
a role in the activation of the adaptive immune system.
Typically, increased MHC variation
- enhances an organism's ability to combat a variety of
infections and diseases.
- As a result, it is associated with increased fitness
