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Alex's Genetics > Lecture 23a > Flashcards

Lecture 23a Flashcards

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Biology 101 flashcards
1
Q

What is a Population Bottleneck?

A

This is when something happens, such as a natural disaster, that causes a drastic decrease in the population regardless of genotype.

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2
Q

How do Population Bottlenecks affect random genetic drift?

A

Population Bottlenecks increase random genetic drift, because the population is often left smaller and more prone to random genetic drift.

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3
Q

What is an example of Population Bottlenecks?

A

The African cheetah has lost nearly all of its genetic variation due to a bottleneck effect that occurred 10,000 - 12,000 years ago.

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4
Q

What is Migration?

A

When a small group of individuals separates from a larger population and establishes a colony in a new location.

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5
Q

What are the 2 consequences of Migration?

A

1) Founding population will have less genetic variation than the original population.
2) Founding population will have different allelic frequencies from the original population due to chance.

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6
Q

What is an example of the Founder Effect?

A

The Old Order Amish of Lancaster County, PA.

A population of 8,000 arose from just 3 couples that immigrated to the US in 1770.

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7
Q

How does the Founder Effect impact genetic diseases?

A

Genetic diseases can be more common due to low genetic variability.

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8
Q

What is an example of how the Founder Effect impacts genetic diseases?

A

The frequency of Ellis-Van Creveld Syndrome (a recessive form of Dwarfism) is 7% in the Old Order Amish, which is much higher than in any other population.

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9
Q

What is Directional Natural Selection?

A

Favors the extreme phenotype and may involve a single gene (insecticide resistance in mosquitos) or multiple genes (selection for large size or quickness).

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10
Q

“Selection for one extreme trait, selection against the other extreme trait.”

What is this?

A

Directional National Selection

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11
Q

What is Disruptive Natural Selection?

A

Multiple phenotypes are favored in diverse environments. There is not one consensus phenotype.

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12
Q

“Different snail shell colors favored depending on where the snail is.”

What is this?

A

Disruptive Natural Selection

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13
Q

“Selection for both extremes. Selection against moderate traits.”

What is this?

A

Disruptive Natural Selection

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14
Q

“Short tails keep predators from catching you on the ground. Long tails are good for balance in trees. Medium tails don’t help.”

What is this?

A

Disruptive Natural Selection

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15
Q

What is Stabilizing Natural Selection?

A

The intermediate phenotype has the highest fitness.

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16
Q

“Birds have lower fitness if they lay too many or too few eggs.”

What is this?

A

Stabilizing Natural Selection

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17
Q

“Selection for moderate traits. Selection against both extremes.”

What is this?

A

Stabilizing Natural Selection

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18
Q

“Short tails mess up the cat’s balance. Long tails drag on the ground. Medium tails are best.”

What is this?

A

Stabilizing Natural Selection

19
Q

What is Balancing Natural Selection?

A

The rare phenotype has the reproductive advantage over more common phenotypes.

20
Q

“Bees have been known to favor less the less commonly colored flower.”

What is this?

A

Balancing Natural Selection

21
Q

T/F: Balancing Natural Selection may involve a homozygous advantage.

A

False! It may involve a heterozygote advantage

22
Q

What is an example of Balancing Natural Selection involving a heterozygote advantage?

A

For a single gene: the sickle cell mutation

23
Q

What is Overdominance?

A

The phenomenon in which a heterozygote is more vigorous than either of the corresponding homozygotes.

24
Q

Overdominance causes and is an example of what?

A

Balancing Selection

25
Q

What type of disorder is Sickle-Cell Anemia?

A

Autosomal recessive disorder

26
Q

What do affected individuals of sickle cell anemia produce?

A

An abnormal form of Hemoglobin

27
Q

What do HbA and HbS encode?

A

HbA encodes the normal hemoglobin, hemoglobin A

HbS encodes the abnormal hemoglobin, hemoglobin S

28
Q

Where has the sickle cell allele most commonly been found?

A

High frequency in parts of Africa where Malaria is found.

29
Q

At the molecular level, what is overdominance due to?

A

Due to 2 alleles that produce slightly different proteins.

30
Q

What does the eukaryotic parasite Plasmodium do?

A

Enters HbA HbA red blood cells and multiplies within them.

31
Q

How does the HbA HbS (heterozygote) genotype protect against Malaria?

A

Red blood cells of heterozygote are likely to rupture when infected by Plasmodium. This prevents the propagation of the parasite.

32
Q

What is Assortative Mating?

A

When sexual reproduction is nonrandom in a population.

33
Q

What is Positive Assortative Mating?

A

When individuals with similar phenotypes reproduce with each other.

34
Q

What is Negative Assortative Mating?

A

When dissimilar phenotypes preferentially reproduce.

35
Q

What is Darwinian Fitness?

A

The relative likelihood that a genotype will survive and contribute to the gene pool of the next generation.

36
Q

Darwinian fitness is a measure of what?

A

Reproductive superiority

Basically, the more individuals reproduce = the fitter they are

37
Q

T/F: Darwinian fitness and physical fitness are the same.

A

False! They should not be confused with each other. Darwinian fitness is more reproductive superiority.

38
Q

Fitness is determined by what?

A

Relative reproductive success

39
Q

What 2 things determine relative reproductive success?

A

1) Natural selection- Those individuals that are most adapted to their particular environment will survive and reproduce
2) Differences in mating efficiency and fertility (need the individual to want to have a lot of offspring)

40
Q

Genotypic classes can be assigned fitness values according to what?

A

According to their reproductive potential

41
Q

What fitness value is the gene with the highest reproductive ability given?

A

1.0

All other genes are in relation to this number, with 1.0 serving as the denominator

42
Q

Suppose the average reproductive success is:
AA - 5 offspring
Aa - 4 offspring
aa - 1 offspring

What are the fitness values of each?

A

WAA = 1.0
WAa = 4/5 = 0.8
Waa = 1/5 = 0.2

43
Q

What variable denotes fitness values?

A

W

44
Q

Differences in reproductive achievement can be due to what 3 things?

A

1) Fittest genotype is more likely to survive
2) Fittest genotype is more likely to mate
3) Fittest genotype is more fertile

Alex's Genetics (38 decks)

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