Lecture 12

Question 1

Founder effect

Answer 1

occurs when a small group leaves home to find new settlements, causing a new colony with different allele frequencies

by chance, it may either lack some alleles or have high frequency of others

Question 2

Non-random mating - preferentially choosing mates within a group causes excess of _____

Answer 2

homozygotes

Question 3

Non-random mating - preferentially choosing mates outside a group causes excess of ______

Answer 3

heterozygotes

Question 4

population bottlenecks

Answer 4

occurs when a large population is drastically reduced in size

Question 5

Does the new population or large ancestral population have a much more restricted gene pool?

Answer 5

The new population

Question 6

mutations

Answer 6

a major and continual source of genetic variation in populations

• can introduce new alleles
• can convert one allele to another

Question 7

Mutation - harmful recessive alleles

Answer 7

mutations reintroduce harmful recessive alleles

harmful recessive alleles are maintained in heterozygotes

Question 8

mutation - genetic load

Answer 8

genetic load is the collection of recessive deleterious alleles present in a population

Question 9

directional selection

Answer 9

causes an allele to increase (or decrease) in frequency over time

Question 10

two cases of natural selection

Answer 10

negative selection
positive selection

both lead to changes in allele frequencies

Question 11

negative selection

Answer 11

reduces frequency of a deleterious trait

Question 12

positive selection

Answer 12

increases frequency of an advantageous trait

Question 13

balanced polymorphism

Answer 13

persistence of harmful recessive alleles due to heterozygotes with increased fitness

Question 14

Heterozygote advantage

Answer 14

another word for balanced polymorphism

-have a reproductive advantage under certain conditions

Question 15

what can directional selection cause?

Answer 15

a deficiency of heterozygotes

Question 16

what can balancing selection cause?

Answer 16

excess of heterozygotes

Question 17

sickle cell disease - what is glutamic acid substituted by?

Answer 17

the gene defect is a known mutation of a singe nucleotide (SNP) (A to T) of the beta-globin gene (exhibits balanced polymorphism), which results in glutamic acid being substituted by valine at position 7

Question 18

sickle cell allele - negative selection

Answer 18

sickle cell allele causes the recessive cell anemia trait (when homozygous), and is therefore under negative selection

Question 19

sickle cell allele - under positive selection

Answer 19

the sickle cell allele helps protect heterozygotes from malaria

Question 20

when did the major groups of mammals first arise?

Answer 20

between 70 and 50 mya

Question 21

what did the asteroid/comet impact 66MYA likely cause?

Answer 21

mass extinction at KT boudnary

Question 22

Aegypotphitecus

Answer 22

• 30-40 MYA
• monkey-like animal (size of a cat)
• found in tropical forests of Africa, tree dweller
• possible ancestors of gibbons, apes, and humans

Question 23

Dryopithecus

Answer 23

• 22-32 MYA
• oak ape
• found in SW and central Europe
• of of the first hominoids
• ancestor to apes and humans
• lived in trees but could walk
• size of a 7 year old, small brains, and pointed snout

Question 24

molecular evolution

Answer 24

the study of evolution through comparison of:

• DNA and protein sequences
• chromosome banding
• genome structure

Question 25

What do fewer DNA sequence changes indicate?

Answer 25

closer relation and more recent divergence

Question 26

molecular clock

Answer 26

the rate of mutation (assuming that rate is constant) between two DNA sequences can be used as a clock to provide a relative measure of time since divergence from a common ancestor

Question 27

human-chimp genome similarity

Answer 27

- proteins differ by 2 amino acids on average - roughly 30% human proteins are identical in sequence to the chimp protein - gene duplication (or delections) account for about 2.7% of genome differences

Question 28

what makes us human

Answer 28

traits defining "humanness" may be rare -keratin gene (affects hair coverage; expressed in chimps and gorillas; nonsense mutation in humans) -speech - FOXP2 gene hemoglobin genes (embryonic --> fetal versions of hemoglobin; longer fetal period, increased brain growth)

Question 29

Where does human lineage specific (HLS) gene change occur?

Answer 29

in the human lineage but noe of the other great apes | -changes may be responsible for specifically human phenotypes.

Question 30

what makes us different?

Answer 30

gene expression not the genome sequence

Question 31

synteny

Answer 31

the correspondence of gene order preserved between two species

Question 32

how many autosomes do great apes have

Answer 32

23

Question 33

Hominin

Answer 33

- fossils from 4-19 MYA scarce | - 6 MYA hominin line split off from other apes

Question 34

3 candidates for first hominin

Answer 34

1) Ardipithecus kadabba (from Ethiopia) 2) Sahelanthropus tchadensis (from Chad) 3) Orrorin tugenensis (from Kenya)