Lesson 7: Sex - Sources of Genotypic Variation

Question 1

how does reduction of variation occur

Answer 1

genetic drift in finite populations (loss of alleles, loss of heterozygosity (inbreeding))

Question 2

sources of allelic variation

Answer 2

mutations

Question 3

sources of genotypic variation

Answer 3

sex (meiosis)

Question 4

heritable variation without changes in the genetic code

Answer 4

epigenetic inheritance

Question 5

sex: shuffling of combinations of alleles

Answer 5

no new alleles, only new genotypes

Question 6

what is sex

Answer 6

meiosis with crossing over + random mating

Question 7

• produces gametes
• separates homologous chromosomes

Answer 7

meiosis

Question 8

exchange of genetic information between the pairs of chromosomes

Answer 8

recombination

Question 9

• shuffling of gametes
• newly formed haploid chromosome come together
• shuffling of allelic combinations into new genotypes

Answer 9

random mating

Question 10

How does meiosis generate genotypic diversity in two ways

Answer 10

1. physical exchange of homologous chromosomal regions (homologous recombination)
2. separation of homologous chromosome pairs allows random and independent shuffling of haploid chromosomes (random mating)

Question 11

process by which a molecule of nucleic acid is broken and then joined to a different one

Answer 11

genetic recombination

Question 12

what does genetic recombination reduce

Answer 12

linkage disequilibrium (LD)

Question 13

how does genetic recombination reduce linkage disequilibrium

Answer 13

mixes up combinations of alleles across loci

Question 14

• increases genotypic variation
• mixes up combinations of alleles at a given locus
• can also help break up LD on different chromatids

Answer 14

random mating

Question 15

Consequence of recombination

Answer 15

reduce linkage disequilibrium

Question 16

• non-random association of alleles at two or more loci, not necessarily on the same chromosome
• occurence of some combinations of alleles or genetic markers in a population more often or less often than would be expected from random formation of haplotypes from alleles based on their frequencies

Answer 16

linkage disequilibrium

Question 17

recombination will break down linkage disequilibrium on ___ chromosome

Answer 17

the same chromosome

Question 18

random mating will break down linkage disequilibrium on ___ chromosome

Answer 18

different chromosome

Question 19

what often cause the nanrandom association of alleles

Answer 19

• natural selection
• genetic drift

Question 20

random mating: create individuals free of deleterious mutations

Answer 20

bring together favorable mutations across loci

Question 21

random mating: deleterious combinations can be selected out of the population

Answer 21

bring together unfavorable mutations across loci

Question 22

tend to last longer

Answer 22

sexual species

Question 23

often good early colonizers of novel habitats because of rapid growth rate

Answer 23

asexual species

Question 24

percent of asexual in eukaryotes

Answer 24

1%

Question 25

Benefits of Sex

Answer 25

1. breakdown linkage disequilibrium
2. increase genotypic variation
3. purge deleterious mutations more easily
4. bring together favorable mutations
5. evolution of “individuality”

Question 26

idea that each person has characteristics that make them different from everyone else in society

Answer 26

Individuality

Question 27

Costs of Sex

Answer 27

1. lower reproductive rate (1/2)
2. have to find mates (not all individuals produce)
3. pass on only 1/2 of genome at each reproduction event
4. death of uniq individuals (genome) in the parental generation