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Genetics > Chapter Two: Extensions to Mendel > Flashcards

Chapter Two: Extensions to Mendel Flashcards

1
Q

dominance is not always ___

A

complete

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2
Q

crosses between true-breeding strains can produce hybrids with phenotypes ___ from both parents

A

different

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3
Q

F1 hybrids that differ from both parents express an intermediate phenotype

A

incomplete dominance

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4
Q

F1 hybrids express phenotype of both parents equally

A

codominance

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5
Q

in incomplete dominance and codominance, phenotypic ratios and genotypic ratios are ___

A

the same

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6
Q

snapdragon flower color is an example of ___

A

incomplete dominance

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7
Q

lentil coat pattern is an example of ___

A

codominance

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8
Q

ABO Blood group is an example of ___

A

codominance

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9
Q

dominance relations affect ___ and have no bearing on the ___ of alleles

A

phenotype
segregation

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10
Q

alleles still segregate ___ even without incomplete dominance

A

randomly

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11
Q

can a gene have more than two alleles

A

yes

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12
Q

genes may have ___ alleles that segregate

A

multiple

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13
Q

although there can be many alleles in a population, each individual carries ___

A

only two of the alleles

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14
Q

there are ___ alleles for blood type and ___ possible genotypes that generate ___ possible phenotypes

A

three
six
four

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15
Q

dominance relations are ___ to a certain pair of alleles

A

unique

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16
Q

in order to establish dominance relations, you perform ___ between ___ of al phenotypes

A

reciprocal crosses
pure-breeding lines

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17
Q

where do new alleles come from

A

mutations

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18
Q

multiple alleles arise spontaneously from ___

A

mutations

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19
Q

chance alterations in genetic material

A

mutations

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20
Q

the percentage of the total number of gene copies represented by one allele

A

allele frequency

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21
Q

allele whose frequency is more than 1%

A

wild-type

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22
Q

allele whose frequency is less than 1%

A

mutant allele

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23
Q

gene with only one wild-type allele

A

monomorphic

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24
Q

gene with more than one wild-type allele

A

polymorphic

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25
Q

one gene may contribute to ___

A

several visible characteristics

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26
Q

when a single gene determines more than one distinct and seemingly unrelated characteristic

A

pleiotropy

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27
Q

a syndrome is defined as something that has many symptoms because ___

A

multiple organ systems are impacted by the disease

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28
Q

type of pleiotropy where alleles produce a visible phenotype and affect viability

A

lethality

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29
Q

alleles that produce viability often produce deviations from typical ___ predicted by mendel’s laws

A

ratios

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30
Q

inheritance of coat color in mice is an example of ___

A

pleiotropy

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31
Q

recessive lethal alleles are not as ___ as other alleles because ___, changes the ___

A

viable
progeny normally don’t survive until birth
ratio

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32
Q

more than ___ mutant alleles have been identified so far for sickle cell

A

400

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33
Q

normally wild type allele for sickle-cell ___

A

HbBA

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34
Q

HbBS allele specifies for an abnormal protein that causes ___

A

sickling along red blood cells

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35
Q

the most common mutant allele for sickle-cell substitutes an amino acid with a ___ for one with a ___, which changes its ___

A

negative charge
neutral charge
shape

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36
Q

HbBS affects more than one ___

A

trait

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37
Q

the advantage of heterozygotes for sickle-cell

A

resistant to malaria

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38
Q

it is difficult to get rid of a ___ when carriers have an advantage

A

deleterious allele

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39
Q

___ can emerge from the combination of alleles of two genes

A

novel phenotypes

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40
Q

two genes work together to produce a phenotype

A

complementary gene action

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41
Q

___ ratio is a phenotypic signature of complementary gene interaction where dominant alleles of two genes act together to produce a trait while the other three genotypic classes do not

A

9:7

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42
Q

a 9:7 ratio demonstrates that ___ must be present to produce a trait

A

one dominant allele of each gene

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43
Q

when one gene’s allele mask the effects of another gene’s alleles

A

epistasis

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44
Q

Labrador retriever coat color is an example of ___

A

recessive epistasis

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45
Q

labrador retrievers:
B allele is ___ and determines ___
b allele is ___ and determines ___
E allele is ___ and determines ___
e allele is ___ and determines ___

A

dominant, black
recessive, brown if homozygous
on a second gene, no effect
recessive, hides brown or black is homozygous

46
Q

9:3:4 is a telltale ratio of ___

A

recessive epistasis

47
Q

the expected phenotypic ratio for recessive epistasis of lab coat color is ___

A

9 black (B_E_): 3 brown (bbE_): 4 gold (__ee)

48
Q

epistasis in human blood groups: two parents who are apparently O can have offspring that are ___ because of the ___

A

type A or B on occasion
bombay phenotype

49
Q

the Bombay phenotype is a ____ at a ___ that masks the phenotype of ___ if it is homozygous recessive

A

mutant recessive allele
second gene
ABO alleles

50
Q

presence of dominance allele at second gene hides the affects of alleles at an original gene

A

dominance epistasis

51
Q

12:3:1 and 13:3 are telltale ratios for ___

A

dominance epistasis

52
Q

it is not always possible to determine ____ mutated in a person with a heterogenous mutant phenotype

A

which of many genes

53
Q

deafness in humans may be caused by a mutant allele at one of more than ___ different genes

A

50

54
Q

___ can determine if mutations arise from the same or different genes

A

complementation testing

55
Q

human deafness: if parents have a defect in the same gene, their offspring will ___. if parents have a defect in different genes, their offspring will ___.

A

all be deaf
possibly be hearing

56
Q

four distinct F2 phenotypes

A

additive

57
Q

when homozygous, recessive allele of one gene masks both alleles of another gene

A

recessive epistasis

58
Q

when homozygous, recessive allele of each gene masks the dominant allele of the other gene

A

reciprocal recessive epistasis

59
Q

dominant allele of one gene hides effects of both alleles of the other gene

A

dominant epistasis I

60
Q

dominant allele of one gene hides effects of dominant allele of another gene

A

dominant epistasis II

61
Q

only one dominant allele of either of two genes is necessary to produce phenotype

A

redundancy

62
Q

how do we know if a trait is caused by one gene or two genes that interact

A

ratios like 9:7 or 13:3 indicate gene interaction
look at different ratios to determine which is correct

63
Q

additive gene interaction ratio

A

9:3:3:1

64
Q

recessive epistasis ratio

A

9:3:4

65
Q

reciprocal recessive epistasis ratio

A

9:7

66
Q

dominant epistasis I ratio

A

12:3:1

67
Q

dominant epistasis II ratio

A

13:3

68
Q

redundancy ratio

A

15:1

69
Q

disease that produces little or not pigmentation in skin, hair, and eyes

A

ocularcutaneous albanism (OCA)

70
Q

the same genotype doesn’t always produce ___

A

the same phenotype

71
Q

phenotype often depends on ___ and ___

A

penetrance and expressivity

72
Q

percentage of a population with a particular genotype that show the expected phenotype

A

penetrance

73
Q

penetrance can be ___ or ___

A

complete or incomplete

74
Q

degree or intensity with which a particular genotype is expressed in a phenotype

A

expressivity

75
Q

have subtle, secondary effect on a phenotype from a major gene

A

modifier genes

76
Q

environment can affect the ___ of a genotype

A

phenotypic expression

77
Q

___ is a common element of the enrichment that affects phenotype

A

temperature

78
Q

example of temperature impacting phenotype

A

coat color in siamese cats is darker in its extremities (legs, tail, ears)

79
Q

why do the colors differ in siamese cats

A

mutation that renders an enzyme involved in melanin synthesis is temperature sensitive

80
Q

change in phenotype arising from environmental agents that mimics the effect of a mutation at a gene

A

phenocopy

81
Q

mutations that are lethal only under some conditions

A

conditional lethal

82
Q

mutant allele has wild-type functions (normal)

A

permissive conditions

83
Q

mutant allele has defective functions

A

restrictive conditions

84
Q

traits determined by segregating alleles of many genes interacting with one another and the environment

A

continuous traits

85
Q

example of continuous traits in humans

A

height and skin color

86
Q

continuous traits are also called ___ and are usually ___

A

quantitative traits
polygenic

87
Q

the more genes that contribute to a trait, the greater number of ___ and the greater similarity to ___

A

possible phenotypes
continuous variation

88
Q

continuous variation phenotypic rations will exhibit a ___

A

bell curve

89
Q

domestic dog coat colors provide a clear example of a ___

A

complex trait

90
Q

there are at least ___ genes that control for coat color and pattern in dogs

A

12

91
Q

skin cells that produce pigments deposited in each dog hair

A

melanocytes

92
Q

melanocytes can produce either ___ or ___

A

dark pigment (eumelanin) or light pigment (pheomelanin)

93
Q

genes E, A, and K control ___

A

the switch between light and dark pigment synthesis in melanocytes

94
Q

genes E and B control ___

A

synthesis and deposition of the dark pigment eumelanin

95
Q

genes S and M control ___

A

spotting

96
Q

the F1 phenotype generated by a pair of alleles defines the ___ between alleles

A

dominance relationship

97
Q

incomplete dominance: F1 resembles ___
codominance: F1 resembles ___

A

neither parent
components of each parent

98
Q

one gene can contribute to ___

A

multiple traits

99
Q

a single gene may have many ___

A

alleles

100
Q

new alleles arise by ___

A

mutation

101
Q

wild type alleles ___ 1% of the population. mutant alleles ___ 1% of the population

A

more then
less then

102
Q

two or more wild type alleles in the population

A

polymorphic gene

103
Q

a gene with only one wild type allele

A

monomorphic

104
Q

two or more genes may interact to produce a ___

A

phenotype

105
Q

when the action of an allele at one gene hides traits normally caused by alleles at another gene

A

epistasis

106
Q

when dominant alleles of two or more genes are required to generate a trait

A

complementary gene action

107
Q

with ___, mutant alleles at any one of two or more genes are sufficient to elicit a phenotype

A

heterogeneity

108
Q

___ can reveal whether a particular phenotype arises from mutations in the same or separate genes

A

complementation tests

109
Q

expression of phenotypes can be modified by ___, ___, or ___

A

environment, chance, or other genes

110
Q

when fewer than 100% of individuals with the same genotype express a specific phenotype

A

incomplete penetrance

111
Q

a phenotype may show ___ when it is expressed at a different level in different individuals with the same genotype

A

variable expressivity

112
Q

a ___ trait can have any value of expression between two extremes, most are ___

A

quantitative
polygenic

Genetics (24 decks)

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