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A BIO106 - EVOLUTIONARY BIOLOGY > Sex > Flashcards

Sex Flashcards

1
Q

Souces of Genotypic Variation

A

Sex

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2
Q

Reduction of Variation

A
  • Genetic Drift in finite populations
  • Loss of alleles
  • Loss of heterozygosity (Inbreeding)
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3
Q

Sources of Allelic Variation

A

Mutations

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4
Q

Heritable variation without changes in the genetic code

A

Epigenetic Inheritance

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5
Q

Sex

A
  • Shuffling of combinations of alleles
  • No new alleles, only new genotypes
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6
Q

What is Sex?

A

Meiosis with Crossing Over + Random Mating

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7
Q

What happends during Sex?

A
  • Meiosis (produce gametes)
  • Random Mating (shuffling the gametes)
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8
Q

What happends during Sex?
In Meiosis

A

Separates homologous chromosomes

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9
Q

What happends during Sex?
In Random Mating

A
  • Newly formed haploid chromosomes (sperm & eggs) come together
  • Shuffling of allelic combinations into new genotypes
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10
Q

Meiosis generates genotypic diversity in two ways:

A

(1) Physical exchange of homologous chromosomal regions
(2) Separation of homologous
chromosome pairs

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11
Q

A process by which a molecule of nucleic acid (usually DNA, but can also be RNA) is broken and then joined to a different one

A

Genetic Recombination

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12
Q

Pairing of homologous chromosomes

A

Synapsis

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13
Q

Consequences of Sex

A
  • Genetic Recombination (reduces LD)
  • Random Mating (increases genotypic variation)
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14
Q

Consequence of Sex
Genetic Recombination:

A

Mixes up combinations of alleles across loci (reduces Linkage Disequilibrium)

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15
Q

Consequence of Sex
Random Mating:

A
  • Mixes up combination of alleles at a given locus (increases genotypic variation
  • can also help break up LD on different chromatids
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16
Q

An important consequence of Eukaryotic Sex

A
  • Meiosis
  • Crossing over
17
Q

The non-random association of alleles at two or more loci, not necessarily on the same chromosome

A

Linkage Disequilibrium

18
Q

Linkage disequilibrium can be caused by ______

A

evolutionary factors such as natural selection and genetic drift

19
Q

_______ will break down linkage
disequilibrium on the ____ chromosome, and _____ _______ on ______ chromosomes

A
  • Recombination
  • same
  • random mating
  • different
20
Q

Why do we care about the LD?

A
  • Useful to know which alleles are commonly associated with one another
  • Patterns of LD can tell us about the evolutionary history of the population
  • Breaking up LD will make a population respond more efficiently to the action of natural selection
21
Q

Random mating during SEX

A
  • The haploid chromosomes (sperm and egg) come together
  • Can get combination of favorable mutations more quickly
  • Can remove unfavorable mutations more quickly
22
Q

Benefits of Sex
Genetic Recombination:

A

Breakdown of Linkage Disequilibrium

23
Q

Benefits of Sex
Random Mating:

A
  • Increase genotypic diversity
  • Bring together favorable mutations across loci
  • Bring together unfavorable mutations across loci
24
Q

Bring together favorable mutations across loci

A

Create individuals free of deleterious mutations

25
Q

Bring together unfavorable mutations across loci

A

Deleterious combinations can be selected out of the population

26
Q

Cost of Sex

A
  • Loss of Fitness relative to clonal populations
  • Reduces population growth rate by 1/2, because males cannot reproduce
27
Q

Sex is not ______

A

universal

28
Q

Sex occurs in ______, and not in ______ or ______

A
  • Eukaryotes
  • Bacteria
  • Archaea
29
Q

It occurs often in plants, and in many invertebrates

A

Asexuality

30
Q

Some eukaryotes are asexual until they experience a large accumulation of ______ ______ (mutational meltdown) or _____, then they have sex

A
  • deleterious mutations
  • stress
31
Q

Some eukaryotes have more than __ sexes (some ciliates have ___)

A
  • 2
  • 32
32
Q

Within Eukaryotes, sexual species tend to last ____

A

longer

33
Q

Asexual species are often ____ ____ ____ of novel habitats because of ___ ____ ____ (many ______ plants are asexual)

A
  • good early colonizers
  • rapid growth rate
  • invasive
34
Q

In Eukaryotes, less than ___ are asexual

A

1%

35
Q

Summary
Benefits of Sex

A
  • Breakdown Linkage Disequilibrium
  • Increase in Genotypic Variation
  • Purge deleterious mutations more easily
  • Bring together favorable mutations
  • Evolution of “individuality”
36
Q

Summary
Costs of Sex

A
  • Lower Reproduction Rate (1/2)
  • Have to find mates (not all individuals reproduce)
  • Pass on only ½ of your genome at each reproduction event
  • Death of unique individuals (genome) in the parental generation

A BIO106 - EVOLUTIONARY BIOLOGY (6 decks)

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