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Genetics > Test 2 > Flashcards

Test 2 Flashcards

1
Q

What is incomplete dominance?

A

when the heterozygote (Aa) has a phenotype that’s in between the phenotypes of two homozygotes (AA or aa)

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2
Q

What is complete dominance?

A

• when the phenotype of Aa and AA are the same.
• only dominant allele is expressed in a heterozygote

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3
Q

What is the phenotypic ratio of two heterozygotes that exhibit incomplete dominance?

A

1:2:1

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4
Q

What is codominance?

A

when the heterozygote simultaneously expresses the phenotype of both homozygotes (AA and aa)

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5
Q

What is incomplete penetrance?

A

when a genotype doesn’t always produce the expected phenotype

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6
Q

What is penetrance?

A

the percentage of individuals having a particular genotype that express the expected phenotype

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7
Q

What is expressivity?

A

the degree to which a trait is expressed

Level in expression

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8
Q

What is a lethal allele?

A

an allele that cause death at an early stage in development

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9
Q

What is a recessive lethal allele?

A

it kills individuals that are homozygous for that allele

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10
Q

What is a dominant lethal allele?

A

the allele kills both heterozygote and homozygote

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11
Q

What is aurea?

A

It’s a recessive lethal allele in plant species that doesn’t allow them to photosynthesize

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12
Q

What are multiple alleles?

A

For a given locus, there are more than two alleles within a group of organisms

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13
Q

What does multiple alleles mean?

A

Each pair has a dominance relationship

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14
Q

How do you calculate the number of genotypes with multiple alleles (n) for diploids?

A

[(n)(n+1)]/2

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15
Q

How do you calculate the number of different homozygotes?

A

n

only one way to get a homozygote

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16
Q

How do you calculate the number of different heterozygotes possible for diploids?

A

[(n)(n-1)]/2

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17
Q

How many different alleles can diploid individual have?

A

Only two different alleles of a gene

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18
Q

What is gene interaction?

A

Interaction between genes at different loci that affect the SAME characteristic

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19
Q

What is epistasis?

A

When a gene at one locus masks or suppresses the effect of a gene at different locus

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20
Q

What is an epistatic gene?

A

The gene that does the masking in epistasis

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21
Q

What is a hypostatic gene?

A

the gene whose expression is being masked

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22
Q

What is recessive epistasis?

A

when the expression of the homozygous recessive (bb) of one gene is epistatic to the expression to the second gene

bb inhibits the expression of an allele

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23
Q

What is dominant epistasis?

A

when the dominant allele expression of a homozygous or heterozygote of one gene is epistatic to the second gene

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24
Q

What is duplicate recessive epistasis?

A

what two recessive alleles at either gene suppress a phenotype

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25
Q

What is duplicate dominant epistasis?

A

When a single dominant allele of either gene is sufficient to mask the second gene

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26
Q

What is dominant with recessive suppressor?

A

When the dominant allele of one gene combines with the suppressor from a second gene that restore the dominant phenotype of the first gene

Suppresses the expression of the first gene

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27
Q

What is the phenotypic ratio for recessive epistasis?

A

9:3:4

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28
Q

What is the phenotypic ratio for dominant epistasis?

A

12:3:1

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29
Q

What is the phenotypic ratio for duplicate recessive epistasis?

A

9:7

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30
Q

What is the phenotypic ratio for duplicate interaction epistasis?

A

9:6:1

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31
Q

What is the phenotypic ratio for duplicate dominant epistasis?

A

15:1

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32
Q

What is the ratio for dominant and recessive epistasis?

A

13:3

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33
Q

What is a sex-linked characteristic?

A

When genes located on the sex chromosomes

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34
Q

What are sex influenced characteristics?

A

when autosomal genes are more readily expressed in one gene. Expression in male and female is different

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35
Q

What is a sex limited characteristic?

A

Autosomal genes whose expression only appears in one sex. Each can carry the genes but is only expressed by one sex

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36
Q

What is genetic maternal effect?

A

When the genotype of the mother determines the PHENOTYPE of the offspring

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37
Q

What is cytoplasmic inheritance?

A

when characteristics are encoded by genes from the cytoplasm, which are inherited only from mom

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38
Q

What is a temperature sensitive allele?

A

an allele whose product function differently in various temperature ranges

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39
Q

What is genomic imprinting?

A

when a gene is expressed differently depending on whether it came from mom or dad

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40
Q

What is a phenocopy?

A

when environmental agent results in an individual of one genotype that mimics expected phenotype of a different genotype

THIS IS NON-HEREDITARY CHANGE

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41
Q

What are discontinuous characteristics?

A

When there are few distinguishable phenotypes. there is separation between the groups

(Round or wrinkled)

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42
Q

What are continuous characteristics?

A

Characteristics that display a large number of possible phenotypes that aren’t easily distinguishable

Ex: human height

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43
Q

What are polygenic characteristics?

A

characteristics that are encoded by genes at MANY LOCI

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44
Q

What is pleiotropy?

A

When one gene affects multiple characteristics

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45
Q

What are dizygotic twins?

A

Non identical twins. Coincidental fertilization of 2 eggs. 50% genetically related

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46
Q

What are monozygotic twins?

A

Identical twins. Single fertilization split of initial embryo. 100% genetically related

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47
Q

What is a concordant trait?

A

The trait shared by both twin members
Same phenotype

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48
Q

What are discordant twins?

A

Only one member has the trait

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49
Q

What is concordance?

A

The percentage of twin pairs that are concordant for a trait

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50
Q

What is an ultrasonography?

A

Ultrasound
High-frequency sound is beamed into uterus, sound waves detect dense tissue and bounce back to transform a picture

51
Q

What is amniocentesis?

A

prenatal test that obtains a sample of amniotic fluid from the uterus

Weeks 15-18, cells are cultured

52
Q

What is chorionic villus sampling?

A

Prenatal testing
A plastic tube comes in contact w the outer layer of the placenta. Suction is applied and a small piece of chorion is removed

53
Q

What is a karyotype?

A

A picture of the complete set of chromosomes

54
Q

What are maternal blood screening tests?

A

Exam level of certain substances in the mothers blood. Only indicates increased risk of a problem

55
Q

What is noninvasive prenatal screening?

A

• cell-free fetal dna
• Tests that use maternal blood
• no risk to fetus or placenta
• ~ 9 weeks

56
Q

What is preimplantation genetic diagnosis?

A

people who carry a genetic defect can avoid producing a child with the disorder

• use of in vitro fertilization

57
Q

What is newborn screening?

A

when newborn infants are tested for genetic disorders
• mandatory bc early identification can lead to effective treatment

58
Q

What is presymptomatic genetic testing?

A

Tests for healthy adults for genes that might predispose them to a genetic condition in the future

59
Q

What is HETerozygote screening?

A

Test healthy members of a population to identify het carriers of a disease-causing allele but have the potential to produce children who have the disease

Their recessive allele can cause disease

60
Q

What is pharmacogenetic screening?

A

• Tailored medicine
• look for alleles that cause positive or negative reaction to treatments

61
Q

What are some complications in interpreting genetic tests?

A

• some diseases are caused by many mutations which are not easily detected with one test
• incomplete penetrance can cause individual phenotype to escape the genotypic expectations

62
Q

Why are humans not an ideal genetic model?

A
  1. small numbers of offspring
  2. cannot make controlled matings
  3. long generation time
  4. difficult to maintain groups in a controlled or similar environment
63
Q

What is a pedigree?

A

Pictorial representation of a family history that outline the inheritance of one or more characteristics

64
Q

What are autosomal recessive traits?

A
  1. Appear in both sexes with equal frequency
  2. Tend to skip generations
  3. Affected offspring are often born to unaffected parents
  4. When parents are het (Aa), 1/4 of offspring will be affected
  5. Appears more in children of consanguineous mates
65
Q

What are autosomal dominant traits?

A
  1. Appear in both sexes with equal frequency
  2. Both sexes transmit trait.
  3. Doesn’t skip generations.
  4. Affected offspring must have affected parent
  5. When one parent (affected) is HET and one parent is unaffected, 1/2 offspring will be affected
  6. Unaffected parents do not transmit trait
66
Q

What are X-linked RECESSIVE traits?

A
  1. Usually more males than females are affected
  2. Affected sons are usually born from unaffected mothers; thus, the trait skips generations.
  3. Approximately half of a carrier (het) mother’s sons are affected.
  4. Never passed from father to son
  5. All daughters of affected fathers are carriers.
67
Q

What are X-linked DOMINANT traits?

A
  1. Both males and females can be affected BUT usually more females
  2. Does NOT skip generations. Affected sons must have an affected mother
    affected daughters must have either an affected mother or an affected father.
  3. Affected fathers pass the trait to all their daughters.
  4. Affected mothers (if heterozygous) pass the trait to 1/2 of their sons and 1/2 of their daughters.
68
Q

What is a Y-linked trait?

A
  1. Only males are affected
  2. Passed from father to all sons
  3. Does not skip generations
69
Q

What is the principle of segregation?

A

States that alleles separate during meiosis

70
Q

What is independent assortment?

A

When alleles at one locus assort independently of alleles at another locus

71
Q

What is recombination?

A

When alleles of different genes can assort into new, non-parental combinations

72
Q

What are linked genes?

A

Genes that are located close together on the same chromosome

73
Q

What is a linkage group?

A

A group of linked genes

74
Q

What are non recombinant gametes?

A

Gamete that contains only the original combinations of alleles that were present in the parents

75
Q

What are cis/coupling genes?

A

When there are two dominant or two recessive alleles on the same chromosome

AB/ab

76
Q

What are trans/repulsion genes?

A

When there are one dominant and one recessive allele on the chromosome

Ab/aB

77
Q

What is the chiasma?

A

The physical position of where crossing over happens between non sister chromatids

78
Q

How do you find the recombination frequency?

A

(# of recombinant progeny/total # progeny) x 100%

79
Q

What did Walter Sutton discover?

A

that genes are physically located on chromosomes

the chromosome theory of inheritance

80
Q

What did Nettie Stevens and Edmund Wilson discover?

A

That sex was associated with a specific chromosome in insects

81
Q

What did Calvin bridges discover?

A

that non disjunction of X chromosomes was related to the inheritance of eye color in Drosophila

82
Q

What did Creighton and McClintock discover?

A

That intrachromosomal recombination was the result of physical exchange between chromosomes

83
Q

What is a three point cross?

A

A cross between a heterozygote at three loci and a homozygous recessive at the same three loci

84
Q

How many classes of phenotypes are possible from a three point cross?

A

8

2^3=8

85
Q

What is interference?

A

a second crossover event adjacent to the first is often less frequent than expencted

86
Q

What is the coefficient of coincidence?

A

The ratio of observed double crossovers to expected crossovers

87
Q

How do you calculate the coefficient of coincidence?

A

• # of observed dco/ # of expected dco

88
Q

How do you find the expected dco?

A

Frequencies of cM between genes X total offspring

89
Q

How do you calculate interference?

A

1- coefficient of coincidence

90
Q

What does the number from the coefficient of coincidence actually mean?

A

That we are only viewing that percentage of double crossovers that we expected

0.6 —> 60% observed dco of expected

91
Q

What does the interference value tell us?

A

The number will tell us that the dco progeny expected will not be observed bc of interference

1-0.6= 0.4
40% dco will not be observed

92
Q

What are recombination hotspots?

A

Where recombination is at least 10 times as high as the average elsewhere in the genome

93
Q

Where can levels of recombination vary?

A

• among species
• among chromosomes of a single species
• between males and females

94
Q

What is mapping with molecular markers?

A

uses DNA sequences as locations instead of organisms or cellulite phenotypes of the alleles

95
Q

What are genome wide-association studies?

A

Looking for nonrandom associations between the presence of a trait

96
Q

What is haplotype?

A

A specific set of linked genetic variants or alleles

97
Q

What is linkage disequilibrium?

A

The nonrandom association between alleles in a HAPLOTYPE

98
Q

What does Giemsa dye reveal?

A

DNA rich in adenine and thymine
Known as G bands

99
Q

What does Quinacrine mustard reveal?

A

The differences in cytosine-guanine and adenine-thymine base pairs

100
Q

What is C banding?

A

It reveals DNA regions of occupied by centromeric heterochromatin

101
Q

What is R bands?

A

Rich in cytosine-guanine base pairs

102
Q

What is aneuploidy?

A

When the number of individual chromosomes is altered

103
Q

What are the four types of chromosome rearrangements?

A
  1. Duplications
  2. Deletions
  3. Inversions
  4. Translocations
104
Q

What is a chromosome duplication?

A

when part of the chromosome has been doubled

105
Q

What’s a tandem duplication?

A

When the duplicated segment is right next to the original segment

AB•CDEFEFG

106
Q

What is a displaced duplication?

A

When the duplicated segment is somewhere else on the chromosome or different chromosome

AB•CDEFGEF

107
Q

What is the Bar mutation?

A

Small duplication on the X chromosome
More Bar region=smaller eyes

108
Q

Why are duplications important in evolution?

A

• They are one way that genes evolve

• the extra copy from the duplication is free to undergo mutation and change

• may acquire enough mutations to assume a new function that benefits the organism

109
Q

What is a chromosome deletion?

A

The loss of a chromosome segment

AB•CDEFG —> AB•CDG

110
Q

What is cri-du-chat syndrome?

A

Heterozygous deletion on the short arm of chromosome 5

111
Q

What is a chromosome inversion?

A

When a chromosome segment is inverted 180°

AB•CDEFG —> AB•CFEDG

112
Q

What are paracentric inversions?

A

When the inversion doesn’t include the centromere

113
Q

What’s are PERIcentric inversions?

A

Inversions that include the centromere

AB•CDEFG —> ADC•BEFG

114
Q

What are translocations?

A

When chromosome segments moved from one chromosome to another or within the the same chromosome

115
Q

What are non reciprocal INTRAchromosomal translocations?

A

When the segment moves to a different place on the SAMEEEE chromosome

116
Q

What are non reciprocal INTERchromosomal translocations?

A

When the segments moves to a new place

117
Q

What is polyploidy?

A

When there is an increase in the # of chromosome sets

118
Q

What is nullisomy?

A

The los of both members of a homologous pair of chromosomes

Example: 2n=46 nullisomic=44 chromosomes
• 2n-2

119
Q

What is monosomy?

A

The loss of a SINGLE chromosome

2n-1

120
Q

What is trisomy?

A

GAIN of a single chromosome

2n+1

121
Q

What is tetrasomy?

A

The gain of two homologous chromosomes

2n+1

122
Q

What psi Prader-Willi syndrome?

A

The los is part of Chromosome 15q from one homolog

Compulsive eating

123
Q

What is position effect?

A

If genes positions are altered, so will their expression

124
Q

What is pseudodominance?

A

The expression of a normally recessive allele due to a deletion on the homologous chromosome

Genetics (11 decks)

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