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Gene Action Flashcards

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1
Q

What is gene action?

A

How the genotype of a particular trait affects the expression in phenotype

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2
Q

What are the types of gene action?

A

non-additive, sex-linked, sex-limited, sex-influences, and additive

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3
Q

What is non-additive?

A

one allele is expressed stronger than the other allele for the phenotype (1 allele controls phenotype?

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4
Q

What are sex-limited traits?

A

expression of this trait is limited to the sex

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5
Q

What are sex-influenced traits?

A

inheritance of a trait appears to be different in the 2 sexes even when they have the same genotype

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6
Q

What are additive traits?

A

two alleles contribute equally to the phenotype

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7
Q

What are sex-linked traits?

A

genes on the sex chromosome determine the phenotype, it affects the way genes are expressed

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8
Q

What are examples of sex-linked traits?

A

hemophilia, colorblindness, and muscular dystrophy

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9
Q

What is are examples of a sex-limited trait?

A

milk production, egg production, and crytorchidism

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10
Q

What is an example of sex-influenced traits?

A

male pattern baldness, horned or polled?

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11
Q

What are qualitative traits controlled by?

A

controlled by one or few genes

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12
Q

Which type of gene action are qualitative traits?

A

non-additive

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13
Q

What are the types of non-additive gene action?

A

complete dominance, incomplete dominance, and epistasis

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14
Q

What is complete dominance?

A

one allele of a pair can mask the expression of the other (recessive)

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15
Q

recessive expression=?

A

homozygous condition

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16
Q

What is an example of complete dominance?

A

Angus cattle have black fur (BB or Bb) and Hereford have red fur (bb)

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17
Q

What is incomplete dominance?

A

when heterozygous, there is a different phenotype

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18
Q

What is an example of incomplete dominance?

A

shorthorn cattle with RR is red, Rr is roan, and rr is white

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19
Q

What are the ratios of a incomplete dominance cross of RrxRr?

A

genotype: 1 RR: 2 Rr: 1 rr
phenotype: 1 red: 2 roan: 1 white

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20
Q

What is a heterozygote phenotype called for goats (long ear x short ear)?

A

medium

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21
Q

What is a heterozygote phenotype called for horse (chestnut x cremello)?

A

palomino

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22
Q

What is a heterozygote called for chickens (black x white)?

A

blue

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23
Q

What is epistasis?

A

interactions between non-allelic genes; the phenotypic effect of genes at one locus is dependent on what alleles are present at another locus distinct from the first locus

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24
Q

What are the types of epistasis?

A

Complete dominance epistasis, recessive epistasis, and no dominance (incomplete dominance)

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25
Q

What is complete dominance epistasis?

A

dominant alleles of one gene control the other

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26
Q

What is recessive epistasis?

A

homozygous recessive alleles of one gene control the other

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27
Q

What is no dominance epistasis?

A

heterozygous acts as a separate phenotype, and affects the other gene

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28
Q

What is sex determined by?

A

inheritance of entire chromosome

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29
Q

trait controlled by locus on X chromosome=?

A

relationship with inheritance of sex

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30
Q

Y chromosome=?

A

very few loci identified as controlling traits unrelated to sec of the individual

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31
Q

What does the X chromosome carry?

A

genes for many traits

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32
Q

What is an example of a sex-linked trait in animals?

A

color in cats

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33
Q

What is sex-linkage?

A

concerned with the inheritance of traits controlled by alleles on X chromosome (trait is affected by gene on sex chromosome)

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34
Q

What is CCB_?

A

bay

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35
Q

What is CcB_?

A

buckskin

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36
Q

What is cc__?

A

cremello

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37
Q

What is Ccbb?

A

palomino

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38
Q

What is CCbb?

A

chestnut

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39
Q

What are example of purebreeding in terms of cat coat color?

A

X linked black cats, also orange

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40
Q

What do orange and black cats intermating result in?

A

tortoise shell

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41
Q

What kind of coat color is tortoise shell?

A

codominance of orange and black alleles

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42
Q

Why are not all black and orange cat offspring torts?

A

must classify kittens by sex and color

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43
Q

How can there be a male tort?

A

XXY chromosome

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44
Q

What is XXY called in humans?

A

Klinefelter syndrome

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45
Q

What must a cat have in order to be a tort?

A

both black and orange alleles

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46
Q

What offspring will female torts produce?

A

different constitutions depending on the genotype of mate

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47
Q

How do females show recessive sex-linked traits?

A

homozygous

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48
Q

How many sons have recessive phenotype of a recessive sex-linked trait when heterozygous mother?

A

50%

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49
Q

How do calico cats work?

A

creation of barr bodies and piebald; x chromosome inactivation

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50
Q

What is piebald?

A

having 3rd color gene, allows for expression of white

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51
Q

What is x chromosome inactivation?

A

for females, only one X needs to be activated. The activated ones will form patch of fur that color

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52
Q

What are barr bodies?

A

inactivated chromosome

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53
Q

How does the presentation of polled or horned appear in males?

A

horned is dominant

54
Q

How does the presentation of polled or horned appear in females?

A

polled is dominant

55
Q

What type of gene action is baldness?

A

sex-influenced

56
Q

What is cryptorchidism?

A

when one (mono-) or both of the testes fail to descend from the abdomen

57
Q

What is pleiotropy?

A

one gene affects more than one trait

58
Q

What is variable expressivity?

A

the existence of more than one grade of trait

59
Q

What is overdominance?

A

interactions between gene alleles resulting in a heterozygote superior to either homozygote for a particular trait; extreme heterozygote

60
Q

What is genetic correlation a result of?

A

1) pleiotropy

2) gene linkage

61
Q

What is grade?

A

range

62
Q

What is an example of overdominance?

A

sickle cell disease; heterozygotes carry sickle cell but don’t have it and are resistant to malaria

63
Q

What is incomplete penetrance?

A

not all animals with a particular genotype exhibit the phenotype for that phenotype

64
Q

What is an example of incomplete penetrance?

A

polydactyly in fowl, humans, dogs, and cats

65
Q

What is variable expression?

A

range of expression of a phenotype

66
Q

What does a lethal gene refer to?

A

embryonic death, shortly after birth

67
Q

What does semi-lethal gene refer to?

A

death before puberty

68
Q

What does detrimental gene refer to?

A

reduction in some measure of fitness or productivity

69
Q

What kind of death is a horse who dies 2 months after birth?

A

lethal

70
Q

Which type of lethal/detrimental gene can be predicted?

A

semi-lethal

71
Q

What type of lethal/detrimental gene do albino giraffes have? Why?

A

detrimental; anti-social behavior and highly detectable

72
Q

What type of lethal/detrimental genes are shorter dwarfism in cattle?

A 
HH= normal
Hh = comprest (slow growing/poor development)-detrimental
hh = semi-lethal (death before puberty)
73
Q

What is an absence of phenotype?

A

when a genotype is lethal it results in no possible phenotype outcome

74
Q

What is an example of absence of phenotype?

A

In platinum foxes, PP is lethal. When crossing Pp x Px you get 2Pp:1pp instead of 1PP:2Pp:1pp

75
Q

What is the early embryonic mortality rate of swine?

A

20-30%

76
Q

What is the early embryonic mortality rate of cattle?

A

10-20%

77
Q

What is gene linkage?

A

a condition where non-allelic genes (different traits) consistently travel together through meiosis and syngamy

78
Q

What is syngamy?

A

the fusion of 2 cells in reproduction

79
Q

How are loci affected by gene linkage?

A

2 loci are linked if they occur on the same chromosome

80
Q

In terms of gene linkage (?) what happens to homologous chromosmes?

A

separated at meiosis; genes on the same chromosome tend to end up in the same gamete

81
Q

What is the exception to gene linkage?

A

crossing over

82
Q

What is crossing over?

A

reciprocal exchange of chromosome segments between homologs

83
Q

What is the crossing over process?

A

mutual breaks occur at identical sites on each chromosome, chromosome fragments are exchanged

84
Q

What is recombination?

A

formation of new combination of genes on a chromosome as a result of crossing over

85
Q

Are cross over events common?

A

multiple are

86
Q

What does the probability of recombination of genes at any two linked loci depend on?

A

the distance between the loci

87
Q

What can the occurrence of crossing over help determine?

A

the sequence of genes on a chromosome

88
Q

Where does crossing over occur more?

A

between distant genes than genes that are close together

89
Q

What are quantitative traits controlled by?

A

many genes

90
Q

What are quantitative traits?

A

expression over continuous range of values

91
Q

What are examples of quantitative traits?

A

milk production and carcass merit

92
Q

What is carcass merit made of?

A

IMF (intramuscular fat), REA (rib eye area), and FT (fat thickness)

93
Q

Are qualitative traits affected by the environment?

A

no

94
Q

Are quantitative traits affected by the environment?

A

largely (housing, nutrition, etc)

95
Q

How do genes contribute to the phenotype in quantitative?

A

each gene contributes a certain amount toward phenotypic expression

96
Q

What are qualitative traits?

A

yes or no trait (there or not there)

97
Q

What are types of quantitative traits in beef cattle?

A

growth rate, carcass trait, reproductive traits

98
Q

What are the factors of growth rate?

A

birth weight, weaning weight, yearling weight, average daily gain (ADG)

99
Q

What are the factors of reproductive traits?

A

calving ease, yearling pregnancy, scrotal circumference, first service conception, stagability

100
Q

What is calving ease?

A

selecting against dystocia

101
Q

Why is scrotal circumference selected for?

A

measure of fertility and relation to the age of puberty in offspring

102
Q

What is first service conception?

A

select for ones who can get pregnant on first service (first AI)

103
Q

What is stagability?

A

produces one calf a year for constantly 3 years

104
Q

What are some reproductive traits for poultry?

A

fertility of eggs, hatchability, laying persistence, age to first egg

105
Q

What does selecting the best offspring do?

A

shift the mean in the positive direction (quantitative)

106
Q

Is heritability a trait?

A

no

107
Q

What is heritability represented by?

A

h^2

108
Q

What are the two senses of heritability?

A

broad and narrow

109
Q

What is the broad sense of heritability?

A

ratio of genetic variance to phenotypic variance

110
Q

What is the formula for the broad sense of heritability?

A

h^2=Vg/(Vg+Ve)

111
Q

What is the narrow sense of heritability?

A

proportion of genes expected to be passed from parent to offspring that contribute to expression of that trait

112
Q

What is the formula for the narrow sense of heritability?

A

h^2=Bv/Vp

113
Q

What is the formula for Vp?

A

Vp=Vg+Ve

114
Q

What is the formula for Vg?

A

Vg = Bv+GCV

115
Q

What does Bv stand for?

A

breeding value

116
Q

What does GCV stand for?

A

gene combination value

117
Q

What is narrow sense of heritability used for? Why?

A

animal breeding because it is more reliable as it looks at breeding value

118
Q

What is broad sense of heritability used for?

A

humans

119
Q

What is h^2 a measure of?

A

additive gene action

120
Q

How is heritability expressed?

A

on a range from 0.01 to 1

121
Q

What is low heritability range?

A

0.01-0.2

122
Q

What is medium/moderate heritability range?

A

0.21-0.4

123
Q

What is high heritability range?

A

> 0.41

124
Q

What traits have low heritability?

A

reproductive, fertility, and survival

125
Q

What traits have medium/high heritability?

A

growth and carcass

126
Q

What does a highly heritable trait mean?

A

high performance animals produce high performing offspring, low performing animals produce low performing offspring

127
Q

What does a lowly heritable trait mean?

A

performance records of parents reveal little progeny performance

128
Q

Are all traits heritable?

A

no, some traits show no phenotypic differences, even though they are genetically determined

129
Q

What is an example of a non-heritable trait? Why?

A

number of legs in dogs, because it is standard for dogs to have 4 (leg length on other hand is heritable)

130
Q

What are the parts of additive gene action?

A

quantitative traits and heritability

Genetics (24 decks)

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