Ch. 12: Genetics and Evolution

Question 1

what are genes

Answer 1

genetic sequences that code for heritable traits which can be passed from one generation to the next

Question 2

how are genes organized

Answer 2

into chromosomes

Question 3

what are alleles

Answer 3

alternative forms of genes

Question 4

what are homologues

Answer 4

the two copies of each chromosome each cell possesses

Question 5

what is a locus

Answer 5

the specific area on a chromosome where a gene/gene info is located

Question 6

what is a homizygous genotype

Answer 6

situation i which only one allele is present for a given gene

ex: parts of the x chromosome in males

Question 7

what occurs during complete dominance

Answer 7

phenotype of one dominant allele masks the phenotype of a recessive allele

Question 8

what occurs during codominance

Answer 8

phenotype two dominant alleles are expressed simultaneously

ex: AB bloodtype

Question 9

what occurs during incomplete dominance

Answer 9

phenotype is an intermediate of the two homozygous phenotypes

ex: red snapdragons = RR, pink snapdragons = Rr, white snapdragons = rr

Question 10

what is penetrance

Answer 10

proportion of a population with a genotype who actually express the phenotype

probability of expressing phenotype if you have the genotype

Question 11

what is expressivity

Answer 11

different phenotypic manifestations across a population with the same genotype

Question 12

what does the law of independent assortment specify

Answer 12

inheritance of one gene does not affect another

mendelian law, complicated by discovery of linked genes

Question 13

what is the gene pool

Answer 13

all of the alleles that exist within a species

Question 14

how does mutation to a DNA sequence affect alleles

Answer 14

can potential result in mutant alleles

Question 15

what is a mutagen

Answer 15

substance that can cause a mutation

Question 16

how many nucleotides are affected in point shift mutations

Answer 16

one nucleotide

Question 17

where do silent mutations usually occur

Answer 17

the wobble position (last nucleotide in a codon)

results in no effect on the final synthesized protein

Question 18

how is the final synthesized protein affected with a missense mutation

Answer 18

appropriate amino acid is switched for another

Question 19

how is the final synthesized protein affect with a nonsense mutation

Answer 19

appropriate amino acid chain is stopped short by AUG (methionine)

Question 20

how is the final synthesized protein affect with a frameshift mutation

Answer 20

appropriate amino acid chain has inserted or deleted sequence due to shift in reading frame

Question 21

how are chromosomal mutations different than point shift mutations

Answer 21

large areas of the chromosome are affected

Question 22

what are deletion mutations

Answer 22

a large segment of DNA is lost from the chromosome

Question 23

what are duplication mutations

Answer 23

a segment of DNA is copied multiple times in the chromosome

Question 24

what are inversion mutations

Answer 24

a segment of DNA is reversed within the chromosome

Question 25

what are insertion mutations

Answer 25

a segment of DNA is moved from one chromosome to another

Question 26

what are translocation mutations

Answer 26

segment of DNA on one chromosome is swapped with that of another chromosome

Question 27

how are genes affected by genetic leakage

Answer 27

genes flow from one species to another during inter-species mating

Question 28

how is the gene pool affected by genetic drift

Answer 28

the composition of the gene pool changes due to chance, usually within isolated/small populations

Question 29

what occurs during the founder effect

Answer 29

a small population of a species becomes physically isolated from the rest d/t changes in the natural environment, resulting in genetic drift of the gene pool

Question 30

what occurs during bottlenecking

Answer 30

the amount of available breeders within a population are suddenly and drastically reduced

Question 31

what gene pool changes result in inbreeding depression

Answer 31

limited genetic variation resulting in reduced fitness of the population

Question 32

what gene pool changes result from outbreeding/outcrossing

Answer 32

introduction of unrelated individuals to a breeding pool, possibly increasing population fitness

Question 33

how many traits are studied in a monohybrid cross

Answer 33

one trait

Question 34

what individuals in a genetic cross are the P generation

Answer 34

the parents, the ones being crossed

Question 35

what individuals in a genetic cross are the F generation

Answer 35

the offspring/filla, the ones being produced

Question 36

when crossing two heterozygotes of a completely dominant trait, what are the genotypic and phenotypic ratios of the offspring?

Answer 36

Rr x Rr genotype - 1:2:1 RR x Rr X rr phenotype - 3:1 RR and Rr x rr

Question 37

what is the phenotypic ratios of offspring for a heterozygous dihybrid cross

Answer 37

TtPp x TtPp phenotype: 9:3:3:1

Question 38

on what chromosome are sex-linked traits carried

Answer 38

seX-linked = X linked, recessive **can occur on Y but very, very rare**

Question 39

what is a chiasma

Answer 39

cross over of genes on homologous chromosomes, more likely with genes further apart on a chromosome

Question 40

what does recombination frequency measure

Answer 40

likelihood that two alleles are separated from each other during crossover

Question 41

what does a genetic map plot

Answer 41

the relative distance between genes on chromosomes

Question 42

what are centimorgans

Answer 42

map units, the distance that corresponded to a 1% increased chance of recombination between two genes 25 map units apart = 25% chance of recombination

Question 43

what is the hardy-weinberg equation

Answer 43

p + q = 1 where p is frequency of dominant allele and q is frequency of the recessive allele therefore... p^2 + 2pq + q^2 = 1

Question 44

what do the criteria for the Hardy-Weinberg principle all imply

Answer 44

study population is NOT undergoing evolution; allele frequency will remain stable over time

Question 45

what does the theory of natural selection imply about a species

Answer 45

certain characteristics/traits of individuals within a species may help those individuals have greater reproductive successes which increases the likelihood of those genes being passed on to offspring

Question 46

how does stabilizing selection impact phenotypes

Answer 46

selection against extremes keeps phenotypes within a certain range

Question 47

how does directional selection impact phenotypes

Answer 47

adaptive pressure shifts phenotype towards an extreme

Question 48

how does disruptive selection impact phenotypes

Answer 48

selection of two extreme phenotypes over the norm

Question 49

what is the effect of adaptive radiation

Answer 49

rapid rise of a number of different species, each with their own niche, from a common ancestor

Question 50

what is the definition of species

Answer 50

the largest group of organisms capable of breeding to form fertile offspring

Question 51

what is accomplished through speciation

Answer 51

a new species is formed