Genetics and Evolution

Question 1

Alleles

Answer 1

alternative forms of a gene

Question 2

Genotypes

Answer 2

combination of alleles one has at a given genetic locus

Homozygous
Heterozygous
Hemizygous –> having one allele ( male sex chromosome)

Question 3

Phenotype

Answer 3

the observable manifestation of the genotype

Question 4

Complete dominance

Answer 4

when the effect of one allele completely masks the effect of another

Question 5

Codominance

Answer 5

has more than one dominant allele (AB blood)

Question 6

Incomplete dominance

Answer 6

has no dominant allele; heterozygotes have an intermediate phenotype

Question 7

Penetrance

Answer 7

the proportion of a population with a given genotype who express this phenotype.

the probability that, given a particular genotype, a person will express the phenotype.

Question 8

Expressivity

Answer 8

the different manifestations of the same genotype across the population.

If expressivity is constant, then all individuals with a given genotype express the same phenotype

If expressivity is variable, then individuals with the same genotype may have different phenotypes.

Question 9

Mendel’s first law of (segregation)

Answer 9

states that an organism has two alleles for each gene, which segregate during meiosis, resulting in gametes carrying only one allele for a trait.

can be seen through monohybrid cross

Question 10

Mendel’s second law of (independent assortment)

Answer 10

states that the inheritance of one allele does not influence the probability of inheriting an allele for a different allele.

can be seen through dihybrid cross

Question 11

Griffith experiment

Answer 11

demonstrated the transforming principle, converting non-virulent live bacteria into virulent bacteria by exposure to heat-killed virulent bacteria

Question 12

Avery-MacLeod experiment

Answer 12

demonstrated the DNA is the genetic material because degradation of DNA led to a cessation of bacterial transformational

Question 13

Hershey-Chase

Answer 13

confirmed that DNA is the genetic material because only radiolabeled DNA could be found in bacteriophage-infected bacteria

Question 14

Point mutation

Answer 14

substituting of one nucleotide for another

Question 15

Silent mutation

Answer 15

has no effect on the protein

Question 16

Missense mutation

Answer 16

results in the substitution of one amino acid for another

Question 17

Nonsense mutation

Answer 17

results in substitution of a stop codon for an amino acid

Question 18

Frameshift mutation

Answer 18

moving three-letter transcriptional reading frame

Question 19

Insertion or deletion

Answer 19

results in a shift in the reading frame, leading to changes for all downstream amino acids.

Question 20

Deletion (chromosomal mutation)

Answer 20

occurs when a large segment of DNA is lost

Question 21

Duplication (chromosomal mutation)

Answer 21

occurs when a segment of DNA is copied multiple times

Question 22

Inversion (chromosomal mutation)

Answer 22

occurs when a segment of DNA is reversed

Question 23

Insertion (chromosomal mutation)

Answer 23

occurs when a segment of DNA is moved from one chromosome to another

Question 24

Translocation (chromosomal mutation)

Answer 24

occurs when a segment of DNA is swapped with a segment of DNA from another chromosome

Question 25

Genetic leakage

Answer 25

the flow of genes between species through hybrid offspring

Question 26

Genetic drift

Answer 26

occurs when the composition of the gene pool changes as a result of chance.

Founder effect –> small population of a species finds itself in reproductive isolation from other populations as a result of natural barriers.

Bottleneck –> suddenly reduce the size of the population available for breeding, b/c breeding group is small, inbreeding.

Question 27

Crossing two heterozygotes with complete dominance

Answer 27

Aa x Aa = 1:2:1 genotypic ratio

3:1 phenotypic ratio

Question 28

Test cross

Answer 28

used to determine an unknown genotype.

The organism with an unknown genotype is crossed with an organism known to be a homozygous recessive.

Question 29

Heterozygous Dihybrid cross: PpTt x PpTt

Answer 29

Phenotypic ratio: 9:3:3:1 , (9 Tall and Purple) (3 Tall and white) (3 dwarf and Purple) (1 dwarf and white)
[12 tall : 4dwarf] [12purple : 4white]

Question 30

Chiasma

Answer 30

further apart two genes are, the more likely it is that there will be a point of crossing over

Question 31

Recombination frequency

Answer 31

the likelihood that two alleles are separated from each other during crossing over.

Question 32

Hardy-Weinburg principle

Answer 32

states that if a population meet certain criteria, then the allele frequencies will remain constant.

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

the equation to use to demonstrate that evolution is not occurring in a population.

Question 33

Conditions to meet Hardy-Weinburg principle

Answer 33

• The population is very large (no genetic drift)
• No mutation that affects the gene pool
• Mating between the individual in the population is random
• No migration of individuals into or out of the population
• The gene in the population are all equally successful at being reproduced

Question 34

Moderon synthesis model (neo-Darwinism)

Answer 34

accounts mutation and recombination as mechanisms of variation and consider differential reproduction to be a mechanism for reproductive success.

Question 35

Inclusive fitness

Answer 35

the measure of an organism’s success in population, based on a number of offspring, success in supporting offspring, and ability of the offspring to then support others.

Question 36

Punctured equilibrium

Answer 36

punctured equilibrium suggests that change in some species occurs in rapid bursts rather than evenly over time.

Question 37

Stabilizing selection

Answer 37

keeps phenotype in a narrow range, excluding extremes

Question 38

Directional selection

Answer 38

move the avg phenotype toward one extreme.

Favors one side more than other

Question 39

Disruptive selection

Answer 39

moves the population toward two different phenotypes at the extremes and can lead to speciation.

Question 40

Polymorphisms

Answer 40

naturally occurring differences in form between members of the same population. such as light and dark coloration in the same species of butterfly.

Question 41

Adaptive radiation

Answer 41

the rapid rise of a number of different species from a common ancestor.

Question 42

Prezygotic mechanisms

Answer 42

prevent the formation of zygote completely.

temporal isolation: breeding at different times
ecological isolation: living in different niches within the same territory
behavioral isolation: lack of attraction between members of two species.
reproductive isolation:
gametic isolation: intercourse occurs, but fertilization cannot occur

Question 43

Postzygotic mechanisms

Answer 43

allow for gamete fusion but yield either nonviable or sterile offspring.

hybrid inviability: formation of the zygote that cannot develop to term.
hybrid sterility: formation of a zygote that cannot reproduce
hybrid breakdown: formation of first-generation hybrid offspring viable and fertile but the second generation are sterile and inviable.

Question 44

Divergent evolution

Answer 44

occurs when two species sharing a common ancestor become more different

Question 45

Parallel evolution

Answer 45

occurs when two species sharing a common ancestor evolve in a similar way due to analogous selection pressures.

Question 46

Convergent evolution

Answer 46

occurs when two species not sharing a recent ancestor evolve to become more similar due to analogous selection pressures.