Chapter 12- Genetics and Evolution

Question 1

homologues

Answer 1

each human possesses two copies of each chromosome (except the male sex chromosome)

Question 2

hemizygous

Answer 2

genotypical situation in which only one allele is present for a given gene (as is the case for parts of the X chromosome in males)

Question 3

incomplete dominance

Answer 3

heterozygote expresses a phenotype that is intermediate between the two homozygous geneotypes.

Question 4

codominance

Answer 4

more than one dominant allele exists for a given gene

Question 5

penetrance

Answer 5

population measure. proportion of individuals in the population carrying the allele who actually express the phenotype

Question 6

expressivity

Answer 6

different manifestations of the same genotype across the population

Question 7

two mechanisms that allow for greater genetic diversity in offspring

Answer 7

segregation and independent assortment (also crossing over)

Question 8

transforming principle

Answer 8

nonvirulent bacteria acquired the ability to form smooth capsules from the dead virulent bacteria (Griffiths experiment)

Question 9

transposons

Answer 9

small piece of DNA that can insert/remove itself from DNA

Question 10

silent mutation

Answer 10

change in nucleotide has no effect on final protein synthesized from the gene

Question 11

degeneracy

Answer 11

wobble in genetic code in the third nucleotide of a codon

Question 12

missense mutation

Answer 12

change in nucleotide results in substituting one amino acid for another in the final protein

Question 13

nonsense mutations

Answer 13

occur when change in nucleotide results in substituting a stop codon for an amino acid in the final protein

Question 14

chromosomal mutations

Answer 14

larger-scale mutations in which larger segments of DNA are affected

Question 15

translocation mutations

Answer 15

occur when a segment of DNA from one chromosome is swapped with a segment of DNA from another chromosome

Question 16

deleterious

Answer 16

detrimental (one class is “inborn errors of metabolism)

Question 17

inborn errors of metabolism

Answer 17

class of deleterious mutations. defects in genes required for metabolism.

Question 18

genetic leakage

Answer 18

flow of genes between species

Question 19

genetic drift

Answer 19

changes in composition of the gene pool due to chance. more common in smaller populations

Question 20

founder effect

Answer 20

more extreme case of genetic drift in which a small population of a species finds itself in reproductive isolation from other populations as a result of a natural barrier/bottlenecks

Question 21

bottlenecks

Answer 21

drastically and suddenly reduce size of population available for breeding

Question 22

what can decrease genetic diversity?

Answer 22

genetic drift, the founder effect, inbreeding

Question 23

inbreeding depression

Answer 23

loss of genetic variation may cause reduced fitness of the population

Question 24

outbreeding/ outcrossing

Answer 24

introduction of unrelated individuals into a breeding group

Question 25

what do P and F stand for?

Answer 25

P generation- parent

F generation- filial (offspring)

Question 26

test cross/ back crosses

Answer 26

when determining an unknown genotype you cross the unknown organism with one that is known to be homozygous recessive

Question 27

unless told otherwise, what is always assumed about X-linked (sex-linked) traits?

Answer 27

that they are recessive (ex: hemophilia)

Question 28

recombination frequency

Answer 28

the likelihood that two alleles are separated from each other during crossing over (roughly proportional to the distance between the genes on the chromosome)

Question 29

in a genetic map what is a map unit and what does it correspond to?

Answer 29

map unit = centimorgan, which corresponds to 1% chance of recombination occurring between two genes.

Question 30

5 criteria met for Hardy-Weinberg equilibrium

Answer 30

MEANS THAT NO EVOLUTION IS OCCURRING

1. large population (no genetic drift)
2. no mutations that affect gene pool
3. mating b/w individuals in the population is random (no sexual selection)
4. no migration of individuals in or out of population
5. genes in population are all equally successful at reproducing

Question 31

Hardy-Weinberg equations

Answer 31

p + q = 1

p^2 + 2pq + q^2 = 1

Question 32

differential reproduction

Answer 32

when mutation/ recombination results in a favorable change then its more likely to pass on to the next generation (opposite is also true)

Question 33

inclusive fitness

Answer 33

measure of an organisms success in the population (based on number of offspring and ability of offspring to support others)— helping others of the same species- promotes idea that altruistic behavior can improve the fitness and success of a species as a whole.

Question 34

punctuated equilibrium

Answer 34

changes in some species occur in rapid bursts rather than evenly over time.

Question 35

stabilizing selection

Answer 35

selecting against extremes (regular bell-curve) - ex: human birth weight

Question 36

directional selection

Answer 36

adaptive pressure can lead to the emergence/ dominance of one extreme phenotype

Question 37

disruptive selection

Answer 37

two extreme phenotypes are selected over the norm

Question 38

adaptive radiation

Answer 38

rapid rise of a number of different species from a common ancestor. allows various species to occupy different niches, which decreases competition for limited resources

Question 39

speciation

Answer 39

formation of a new species through evolution

Question 40

pre and post-zygotic mechanisms resulting from reproductive isolation

Answer 40

pre- prevent formation of zygote

post- allow for gamete fusion but yield either nonviable or sterile offspring

Question 41

divergent evolution

Answer 41

two species with common ancestor become less similar b/c of different evolutionary pressures

Question 42

parallel evolution

Answer 42

two species with a common ancestor remain similar because of similar evolutionary pressures

Question 43

convergent evolution

Answer 43

two species with no recent common ancestor become more similar b/c of similar evolutionary pressures

Question 44

molecular clock model

Answer 44

degree of difference in the genome b/w two species is related to the amount of time since the two species broke off from a common ancestor