Chapter 8

Question 1

character

Answer 1

an observable physical feature

Question 2

trait

Answer 2

a particular form of a character

Question 3

parental generation

Answer 3

designated by the letter P

Question 4

first filial generation

Answer 4

designated by F1, these plants are the offspring of the P generation

Question 5

monohybrid cross

Answer 5

crossing paternal varieties with contrasting traits for a single character

Question 6

alleles

Answer 6

the different forms of a gene

Question 7

dominant

Answer 7

determines the phenotype for heterozygous and homozygous dominant

Question 8

recessive

Answer 8

determines the phenotype for homozygous recessive only

Question 9

homozygous

Answer 9

has two alleles that are the same

Question 10

heterozygous

Answer 10

has two different alleles

Question 11

phenotype

Answer 11

physical appearance of an organism

Question 12

genotype

Answer 12

genetic constitution of the organism

Question 13

law of segregation

Answer 13

when any individual produces gametes, the two copies of a gene separate, so each gamete receives only one copy

Question 14

Punnett square

Answer 14

method that ensures we consider all possible random combinations of gametes when calculating expected genotype frequencies

Question 15

test cross

Answer 15

used to determine whether an individual showing a dominant trait is homozygous or heterozygous

Question 16

dihybrid cross

Answer 16

cross between individuals that are identical double heterozygotes

Question 17

dihybrid cross phenotype ratio

Answer 17

9:3:3:1

Question 18

multiplication rule

Answer 18

the probability of two independent outcomes occurring together is found by multiplying the two individual probabilities

Question 19

addition rule

Answer 19

the probability of an event that can occur in two or more different ways is the sum of the individual probabilities of those ways

Question 20

pedigrees

Answer 20

family trees that show the occurrence of inherited phenotypes in several generations of related individuals

Question 21

mutations

Answer 21

rare, stable, and inherited changes in the genetic material

Question 22

wild type

Answer 22

the allele that is present in most individuals in nature

Question 23

polymorphic

Answer 23

a gene with a wild-type allele that is present less than 99 percent of the time

Question 24

incomplete dominance

Answer 24

heterozygotes have an intermediate phenotype

Question 25

codominance

Answer 25

when two alleles of a gene both produce their phenotypes when present in a heterozygote

Question 26

epistasis

Answer 26

occurs when the phenotypic expression of one gene is affected by another gene

Question 27

heterosis

Answer 27

hybrid vigor, when genes interact in a dramatic way

Question 28

What is the general relationship between phenotypes and genes?

Answer 28

most complex phenotypes are determined by multiple genes

Question 29

quantitative traits

Answer 29

traits conferred by multiple genes that need to be measured rather than assessed qualitatively

Question 30

How is the phenotype of an organism truly determined?

Answer 30

by both genotype and environment

Question 31

penetrance

Answer 31

the proportion of individuals in a group with a given genotype that actually show the expected phenotype

Question 32

expressivity

Answer 32

the degree to which a genotype is expressed in an individual

Question 33

heritability

Answer 33

the relative contribution of genetic versus environmental factors to the variation in that character in a particular population (typically varies from 0 to 1)

Question 34

locus

Answer 34

the particular site on a chromosome where a gene resides

Question 35

The ________ of genes on a single chromosome alters their pattern of inheritance

Answer 35

genetic linkage

Question 36

recombinant

Answer 36

two homologous chromosomes can physically exchange corresponding segments during prophase I of meiosis by crossing over

Question 37

recombination frequency

Answer 37

calculated by dividing the number of recombinant progeny by the total number of progeny

Question 38

autosomes

Answer 38

all the chromosomes that aren't sex chromosomes

Question 39

sex chromosomes

Answer 39

determine the sex of the fly

Question 40

hemizygous

Answer 40

any gene that is present as a single copy in a diploid organism

Question 41

sex-linked inheritance

Answer 41

inheritance of a gene that is carried on a sex chromosome

Question 42

What organelles contain genetic material?

Answer 42

nucleus, mitochondria and plastids

Question 43

How many genes are there in the nuclear genome for humans?

Answer 43

21,000

Question 44

How many genes are there in the mitochondrial genome for humans?

Answer 44

37

Question 45

In most organisms, the mitochondria and plastids are inherited only from the ______.

Answer 45

mother

Question 46

horizontal/lateral gene transfer

Answer 46

the transfer of genes from one individual organism to another without sexual reproduction

Question 47

sex pilius

Answer 47

extends from one cell to another cell and draws them together

Question 48

conjugation tube

Answer 48

a thin cytoplasmic bridge that allows genetic material to pass from the donor to the recipient

Question 49

bacterial conjugation

Answer 49

the process where the donor transfers genetic material to the recipient (not the other way around)

Question 50

What happens when the donor DNA is inside the recipient cell?

Answer 50

it can recombine with the recipients DNA

Question 51

plasmids

Answer 51

smaller, circular DNA molecules in bacteria that replicate independently inside the cell

Question 52

How do plasmids replicate?

Answer 52

independently of the main chromosome

Question 53

Do plasmids need to recombine with the main chromosome to add their genes to the recipient cell's genome?

Answer 53

no

Question 54

Plasmids can move between cells during ______, thereby transferring new genes to the recipient bacterium.

Answer 54

conjugation