Lecture 12 Flashcards Preview

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Flashcards in Lecture 12 Deck (34):
1

Founder effect

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

2

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

homozygotes

3

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

heterozygotes

4

population bottlenecks

occurs when a large population is drastically reduced in size

5

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

The new population

6

mutations

a major and continual source of genetic variation in populations
-can introduce new alleles
-can convert one allele to another

7

Mutation - harmful recessive alleles

mutations reintroduce harmful recessive alleles

harmful recessive alleles are maintained in heterozygotes

8

mutation - genetic load

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

9

directional selection

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

10

two cases of natural selection

negative selection
positive selection

both lead to changes in allele frequencies

11

negative selection

reduces frequency of a deleterious trait

12

positive selection

increases frequency of an advantageous trait

13

balanced polymorphism

persistence of harmful recessive alleles due to heterozygotes with increased fitness

14

Heterozygote advantage

another word for balanced polymorphism
-have a reproductive advantage under certain conditions

15

what can directional selection cause?

a deficiency of heterozygotes

16

what can balancing selection cause?

excess of heterozygotes

17

sickle cell disease - what is glutamic acid substituted by?

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

18

sickle cell allele - negative selection

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

19

sickle cell allele - under positive selection

the sickle cell allele helps protect heterozygotes from malaria

20

when did the major groups of mammals first arise?

between 70 and 50 mya

21

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

mass extinction at KT boudnary

22

Aegypotphitecus

-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

23

Dryopithecus

-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

24

molecular evolution

the study of evolution through comparison of:
-DNA and protein sequences
-chromosome banding
-genome structure

25

What do fewer DNA sequence changes indicate?

closer relation and more recent divergence

26

molecular clock

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

27

human-chimp genome similarity

-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

28

what makes us human

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)

29

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

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

30

what makes us different?

gene expression not the genome sequence

31

synteny

the correspondence of gene order preserved between two species

32

how many autosomes do great apes have

23

33

Hominin

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

34

3 candidates for first hominin

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