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AUDE 5310 Embryology & Genetic Conditions > Patterns of Inheritance > Flashcards

Patterns of Inheritance Flashcards

1
Q

what is locus

A

specific location of a gene or DNA sequence on a chromosome

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2
Q

homozygous

A

carrying identical alleles for 1 or more genes

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3
Q

heterozygous

A

carrying 2 different alleles for 1 or more genes

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4
Q

what is heterogeneity and examples

A

many different genes that lead to the same phenotype
ex: hearing loss
blood clotthing disorders
blindness

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5
Q

the address of a gene on a chromosome

A

locus

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6
Q

short arm of chromosome

A

p

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7
Q

long arm of chromosome

A

q

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8
Q

what is a region on chromosome

A

each arm is subdivided into numbered regions
begin from centromere

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9
Q

what is a band on chromosome

A

in each region identified by numbers

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10
Q

how do you read 1q2.4

A

chromosome 1, long arm q, region 2, band 4

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11
Q

same chromosomes are

A

homologous

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12
Q

homozygous

A

means you inherited two identical versions of a particular gene

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13
Q

heterozygous

A

alleles are different

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14
Q

people who have recessive traits (blue eyes, red hair, etc.) are always ___ for that gene

A

homozygous

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15
Q

refers to a degree of correspondence or similarity

A

homologous

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16
Q

refers to an organism in which both copies of a given gene have the same allele.

A

homozygous

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17
Q

Different gene from each parent on each chromosome

A

heterozygous

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18
Q

ploidy

A

number

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19
Q

what is a diploid cell

A

Double the number of chromosomes found in a mature germ cell, which is a haploid cell (23 chromosomes)
Human somatic cells are diploid cells with 23 pairs of chromosomes (46 individual chromosomes)
44 somatic and two germ chromosomes (XX or XY)

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20
Q

germ cells

A

egg and sperm
haploid cells with half the number of chromosomes as the somatic cells

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21
Q

where do we see aneuploidy

A

in somatic cellsw

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22
Q

what is aneuploidy

A

abnormal number or shape

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23
Q

how does aneuploidy occur

A

during cell division when chromosomes don’t separate equally bw 2 daughter cells

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24
Q

when do we see a chromosomal abnormality that results in genetic disorders

A

due to missing or extra chromosomes

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25
Q

what are 3 results that can be seen with aneuploidy

A

Monosomic condition (only one copy of a chromosome is present instead of two; 2n - 1)
Trisomic condition (one extra copy of a chromosome; 2n + 1)
Nullisomic condition (no chromosome of that chromosome pair is present; 2n -2) - generally a lethal condition

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26
Q

what is a monosomic condition

A

only one copy of chromosome present instead of two
2n-1

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27
Q

what is trisomic condition

A

one extra copy of chromosome
2n+1

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28
Q

what is nullisomic condition

A

no chromosome of that chromosome pair present
2n-2
usually lethal

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29
Q

what are the most common aneuploidy

A

trisomy 21, 18, 13

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30
Q

what is a knockout mouse and what is it used for

A

genetically engineered mouse with specific gene(s) artificially deleted or inactivated from its genome
Knock out mice have been used to study many human diseases including cancer and hearing loss

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31
Q

what is cellular homeostasis

A

tendency of an organism/cell to regulate its internal conditions, such as the chemical composition of its body fluids, so as to maintain health and functioning, regardless of external conditions

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32
Q

what is a phenocopy

A

environmentally caused trait that mimics a genetically determined trait
mimics a genetically disorder but is not genetically transferred

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33
Q

what are examples of phenocopy

A

Thalidomide exposure
a phenocopy of phocomelia

Hair loss from chemotherapy
phenocopy of the genetic disorder alopecia

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34
Q

what is pleiotropy

A

diverse effects of one gene or gene pair on several organ systems and functions resulting in multiple phenotypic effects in the body

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35
Q

what is marfan’s syndrome

A

autosomal dom genetic disorder of connective tissue
ex of pleiotropy

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36
Q

symptoms of marfan’s

A

tall, thin, long fingers, heart problems, dislocated lenses of the eyes, speech disorders

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37
Q

how do we classify genetic disorders

A

chromosomal abnormalities (number, structure)
by single gene defect (autosomal dominant, recessive, x linked dom and recessive and y linked)
mitochondrial genetic defect
multifactorial/polygenic defects
environmental influences

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38
Q

how are human chromosomes grouped

A

size/centromere location

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39
Q

size of chromosomes goes

A

largest to smallest

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40
Q

subcentric/submetacentric

A

chrom p & q arms lengths are unequal

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41
Q

metacentric

A

2 arms of chrom roughly equal in length

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42
Q

acrocentric

A

p arm so short it is hard to observe
these are 13, 14, 21, 22, and Y

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43
Q

what chrom are acrocentric

A

13, 14, 21, 22, Y

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44
Q

telocentric

A

centromere @ end of chrom
not in humans

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45
Q

holocentric

A

entire length of chrom is centromere
in nematodes (worms) not humans

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46
Q

when should chromosomal studies be performed

A

individuals iwth multiple malformations or unknown overall diagnosis

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47
Q

an individual with only ____ anomalies is unlikely to have a chromosomal abnoramlity

A

2

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48
Q

chromosomal abnormalities have adverse effects on _____ parts/structures of the body

A

many

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49
Q

who would be a candidate for chromosomal abnormalities

A

pre or post natal onset growth deficiencies and intellectual disabilities

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50
Q

Would individuals with normal growth patterns, psychomotor development, and intelligence be candidates for chromosomal abnormalities

A

nO

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51
Q

what is mendelian/monogenetic inheritance

A

inheritance of conditions caused by mutation to a SINGLE gene

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52
Q

what is the first law of mendelian called

A

law of segregation

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53
Q

what is the general phenotype of people with chrom abnorm?

A

more than 2 systems involved and intellectual disabilities and abnormal growth patters

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54
Q

what proteins coded by genes are involved in function in the ear and HL

A

Cochlear fluid homeostasis
Ionic channels
Stereocilia morphology and function
Synaptic transmission (inner ear to CN8)
Gene regulation

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55
Q

one gene in a gene pair is mutated

A

autosomal dominant

56
Q

who can pass on a AD gene

A

either mom or dad, whoever has the phenotype

57
Q

vertical transmission

A

AD

58
Q

What is meant by vertical transmission

A

each generation has a mutation

59
Q

which trait is the easiest to detect

A

AD

60
Q

affected individuals of AD are

A

heterozygotes

61
Q

what are characteristics of AD

A

Vertical transmission
50% risk to offspring per pregnancy
Unaffected individuals cannot transmit the disease
Males and females equally affected
Variable expressivity and penetrance

62
Q

why is AD 50% chance?

A

father and mom can only pass down one gene out of two , so they have a 50% chance so there is only 4 genes and 1
each of the 4 offspring had a 50% of getting the disease

63
Q

what is meant by 50% risk in AD?

A

50% risk of passing it on to EACH person

64
Q

what is meant by expressivity

A

severity of the condition in that affected individual

65
Q

what is penetrance

A

frequency of occurance
usually a percentage

66
Q

either you show it or you do not

A

penetrance

67
Q

will show but in varying forms of severity

A

expressivity

68
Q

What are characteristics of AD traits

A

Only one copy of the gene is needed to produce the phenotype; affected individuals are heterozygotes

Chance of occurrence per pregnancy is ½ (50%)

Vertical family pattern

Persons with the trait have a parent with the trait unless they represent a spontaneous mutation

If the line is broken it stays broken

Incomplete penetrance

Variable expressivity

Male : female = 1:1

69
Q

what is an example of a variable expression of phenotype

A

waardenburg syndrome

70
Q

Two identical copies of the gene are required

A

autosomal recessive

71
Q

25% chance of occurrence per pregnancy

A

AR

72
Q

which inheritance do we see carriers

A

AR

73
Q

where is consanguinity common

A

AR

74
Q

what pattern do we see in AR

A

horizontal

75
Q

what is the Founder effect?

A

they have the same ancestor and mate within their community and a lot of the individuals carry the recessive trait

Shared genetic ancestry/limited gene pool resulting in genetic conditions seen far more commonly in certain ethnic groups

76
Q

give an example of a founder’s effect

A

Tay Sach’s disesase, a lethal neurodegenerative disease see approx 1:31 for the general population vs Ashkenazi Jews

77
Q

what are characteristics of ARtraits

A

Two copies of the gene are required – homozygous offspring

Chance of recurrence ¼ (25%)

Carrier (heterozygous) parents

Horizontal family pattern

Either the male or female partner can transmit the trait

Male : Female 1:1

78
Q

what is an obligate carrier

A

both parents have to be carriers in order for the offspring to inherit the trait

79
Q

Mates related to each other by blood

A

consanguinity

80
Q

what is a pseudo dominance

A

A situation in which inheritance of an autosomal recessive trait mimics an autosomal dominant pattern; one recessive allele could cause expression of the trait
only in x linked inheritance of male because a male has an x and a y so if they get one bad x, there is no other x so it acts like a dominant trait

81
Q

where would we see pseudo dominance

A

in the case of x linked recessive inheritance in male offspring
hemophilia and color blindness

82
Q

when do we see x linked recessive

A

if the females are carriers with no sign of disease

83
Q

when would we see x linked dominant

A

if females manifest some signs of the disorder

84
Q

Traits controlled by genes on the X chromosome are defined as dominant or recessive by

A

the phenotype of the females

85
Q

who is more affecteed by x linked disorders

A

males

86
Q

affected males of x linked can only have

A

carrier daughters if recessive

87
Q

when will males transmit x linked trait to daughters

A

if it is dominant

88
Q

is there male to male transmission in x linked traits and why

A

NO they can only give a y

89
Q

Men are _____ for all genes on the X chromosome

A

hemizygous

90
Q

why are men hemizygous for all genes on x

A

because they have different chromosomes
neither hetero or homo for x chromosome

91
Q

why does a gene error on x cause a disease in men

A

Because there is no corresponding paired X chromosome with a good gene to balance the bad gene making males affected - psuedo-dominance

92
Q

why are females. only carriers in x linked recessive

A

corresponding paired X chromosome with a good gene to balance the bad gene, makes females only carriers

93
Q

how many copies of a gene is needed to produce the phenotype in AD

A

one

94
Q

affected individuals in AD are

A

heterozygotes

95
Q

what is the chance of occurrence per pregnancy in AD

A

50%

96
Q

what is expressivity in AD

A

variable

97
Q

what is expressivity? what is penetrance?

A

Exp: Series of signs and symptoms that can occur in different people with the same genetic condition
Determines how much the trait affects or how many features of the trait appear in the person

Pene: Complete or incomplete
Proportion of people with a specific genotype who manifest the phenotype

98
Q

what is an example of AR

A

cystic fibrosis

99
Q

what is non complementary AR mating

A

both parents have the same alleles and same recessive form (deafness for ex) so all of their children will have that trait (like deafness)
each offspring has 100% chance of being affected

100
Q

what is hemizygous? give an example

A

only one copy of a gene rather than the usual two
males because they have XY

101
Q

what is multifactorial

A

traits resulting from the interplay of multiple environmental factors with multiple genes
most commonly associated with sporadic gene mutations

102
Q

what is an example of multifactorial inheritance

A

oculo auricular vertebral spectrum disorder

103
Q

what is an obligate carrier?

A

parents of children with the recessive disorder phenotype
parents are normal but carry one mutant gene with offspring that show the phenotype

104
Q

what is a carrier

A

anyone else in a family who has one mutant gene

105
Q

How is an obligate carrier and carrier represented in a pedigree

A

either filled in half or with a dot in the middle

106
Q

what does heterozygotes for an autosomal trait mean

A

they are carriers but do not express the phenotype of the disorder

107
Q

what is another name for mitochondrial transmission

A

the eve gene

108
Q

why are mitochondrial traits inherited from mothers only

A

Because sperms shed their cytoplasm during fertilization they do not contribute mitochondria to the offspring only the mothers do

109
Q

who are at risk of mitochondrial disorders

A

all children of mothers affected are affected
100% transmission

110
Q

will children of fathers with a mitochondrial trait inherit it

A

no

111
Q

what are examples of mitochondrial disorders

A

predisposition to deafness from increased susceptibility to aminoglycoside ototoxicity

112
Q

can aminoglycoside be inherited

A

YES

113
Q

What are the two main traits of mitochondrial disorders

A

only passed on from the mom (eve gene)
every offspring, both genders, has 100% chance of being affected

114
Q

what is genomic imprinting

A

process which a phenotype is different depending on which parent transmits the allele

115
Q

give examples of genomic imprinting

A

prader willi syndrome (paternal)
angelman syndrome (maternal)

116
Q

what is prader willi syndrome

A

a genomic imprinting syndrome
from deletion of chrom 15 inherited from DAD
intellectual disabilities, obesity and uncontrollable eating, orthopedic issues in later life, doesn’t enter puberty and cannot reproduce

117
Q

what is angelman syndrome

A

a genomic imprinting syndrome
from deletion of chrom 15 inherited fromMOM
intellectual disability, developmental delay, uncontrollable and excessive laughing, gait ataxia, seizures

118
Q

what is anticipation

A

worsening of symptoms of a genetic disease from one generation to the next

119
Q

what is allelic expansion

A

an increase in gene size

120
Q

what causes allelic expansion

A

increase in the number of trinucleotide base sequences

121
Q

Increasing bases to increase the gene size

A

allelic expansion

122
Q

give an example of allelic expansion

A

myotonic dystrophy

123
Q

what is myotonic dystrophy

A

muscle disease featuring an inability to relax muscles at will
autosomal dominant
vertical transmission scene with differing severity (generation 10 would be more severe than generation 1)

124
Q

clinical signs of myotonic dystrophy

A

drooping eyelids
facial weakness
mild to severe muscle weakness

125
Q

what is huntingdon’s disease

A

autosomal dominant
seen in ash jewish community the most
50% chance of inheritance

126
Q

clinical signs of huntingdon’s disease

A

adult onset
loss of muscle coordination and control
deterioration of intellectual function
generally early death

127
Q

what is fragile x syndrome

A

x linked dom pattern (varying expressivity)
tip of x chromosome has a fragile site

128
Q

are both males and females affected by fragile x

A

yes, but males have more severe symptoms than females

129
Q

clinical signs of fragile x

A

intellectual disability
delayed development of S/L
may have ADHD
long jaw, big head, large ears

130
Q

what is the most common form of inherited intellectual disability in boys

A

fragile x

131
Q

what is a silent mutation

A

a mutation but still get the end result we want (same protein)

132
Q

what is nonsense mutation

A

causes it to make a stop protein and truncated proteins

133
Q

what is a non conservative mutation

A

Have a mutation and end with a different protein product that is too different and cannot have the same function the protein was supposed to do
Could be conditional lethal

134
Q

what is conservative mutation

A

Have a mutation and end with a different protein product but still gets the job done
Usually no phenotypic change

135
Q

what are examples of point mutations

A

silent, nonsense missense

136
Q

what are missense mutations

A

conservative and nonconservative

137
Q

what is the difference between pleiotropy and chromosomal disorders

A

Pleiotropy is the diverse effects of one gene or gene pair on several organ systems and functions resulting in multiple phenotypic effects in the body
whereas C.D. are multiple genes or chromosomes that affect multiple systems and have adverse effects on many systems/structures and most people have intellectual disabilities and abnormal growth patterns

AUDE 5310 Embryology & Genetic Conditions (18 decks)

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