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5310 - Embryology > Quiz: Lecture 7 & 8 > Flashcards

Quiz: Lecture 7 & 8 Flashcards

Patterns of Inheritance

1
Q

pedigree

A

objective is to show the history of inherited traits through generations
- frequently rule out a certain mode of inheritance but not prove

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2
Q

What information must be included on the pedigree?

A
  • proband
  • race/ethnicity
  • name or initials (numbers for HIPPA)
  • affected status (person with trait/disease)
    -age of all family members/age at death (cause of death)
  • adoption status
  • pregnancy/abortion
    -consanguinity
  • marriage/divorce
  • date pedigree obtained
  • key to shading of symbols
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3
Q

Proband

A

The person being studied
- is the consultant if relaying the history
- the first affected family member seeking help

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4
Q

what is an obligate carrier

A

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

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5
Q

pedigree construction

A

(look at cheat sheet)

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6
Q

consanguinity

A

mating with close relatives

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7
Q

degrees of consanguinity

A

First degree = parents

Second degree = siblings

Third degree = first cousins/aunts and uncles

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8
Q

Monozygotic twins

A

Twins that develop from a single fertilized egg (identical twins of the same gender)

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9
Q

why do monozygotic twins occur?

A

Occurs b/c of the splitting of the zygote at any stage of development
- implant separately
- each has it’s own placenta

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10
Q

dizygotic twins

A

Develop from simultaneous shedding of two ooctyes.
- fertilized by different sperm
- fraternal twins

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11
Q

Locus

A

specific location of a gene or DNA sequence on a chromosome
- chromosome number, arm, region and band

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12
Q

Arm: P

A

short arm

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13
Q

Arm: q

A

long arm

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14
Q

How would you read 1q2.4

A

Chromosome 1, long arm, region 2, band 4

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15
Q

Homozygous

A

identical allele
- same gene from each parent on each chromosome

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16
Q

Heterozygous

A

alleles are different
- different gene from each parent on each chromosome
- 1 good, 1 bad

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17
Q

heterogeneity

A

many genes can lead to the same phenotype
-for example HL/deafness has tons of genes that can result in it

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18
Q

Wild type allele vs Mutant allele

A

Wild: Normal
Mutant: Abnormal

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19
Q

Diplod

A

double number of chromosomes found in a mature germ cell
-somatic has 46 (23 pairs)

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20
Q

Germ cells

A

egg & sperm
-haploid with half the number of chromosomes (23)

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21
Q

Aneuploidy

A

abnormal number of chromosomes, can be extra or missing

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22
Q

what are 3 results that can be seen with aneuploidy

A
  1. Monosomic condition
  2. Trisomic condition
  3. Nullisomic condition
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23
Q

Monosomic condition

A

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

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24
Q

Trisomic condition

A

one extra copy of chromosome
2n+1

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25
Q

Nullisomic condition

A

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

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26
Q

Most common aneuploidy

A

Trisomy 21,18, & 13

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27
Q

knockout mouse

A

genetically engineered mouse with specific genes artificially deleted

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28
Q

cellular homeostasis

A

tendency of a cell or organisms to regulate its internal conditions, such as chemical composition of body fluids, to maintain health and functioning regardless of external conditions

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29
Q

phenocopy

A

environmentally caused trait that mimics a genetically determined traits
-mimics genetic condition but not inherited
-ex. hair loss from chemotherapy can mimic the phenotype of alopecia

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30
Q

pleiotropy

A

when one gene influences two or more seemingly unrelated phenotypic traits.
- when ONE gene exhibits multiple phenotypic expressions
-all syndromic due to affecting multiple organs

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31
Q

Example of Pleiotropy

A

Marfan’s Syndrome
genetic disorder of connective tissue (that develops into a lot of things within the body)

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32
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 (spontaneous mutation)
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33
Q

how are human chromosomes grouped

A

size (largest to smallest)/centromere location

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34
Q

subcentric or submetacentric

A

the chromosomes p and q arms are unequal lengths

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35
Q

metacentric

A

the two arms of chromosomes are roughly equal in length

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36
Q

acrocentric

A

p arm is so short its hard to see, but still present

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37
Q

what chromosomes in humans are acrocentric?

A

chromosomes 13,14,15,21,22,& Y

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38
Q

telocentric

A

the centromere is located at the terminal end of the chromosomes
-not present within humans

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39
Q

holocentric

A

entire length of the chromosome acts as the centromere
-found within worms and not within humans

40
Q

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

A

2

41
Q

who would be a candidate for chromosomal abnormalities

A

people who have pre or post natal onset growth deficiencies and intellectual disabilities

42
Q

who would NOT be a candidate for chromosomal abnormalities

A

individuals with normal growth patterns, psychomotor development, & intelligence

43
Q

Mendelian/Monogenetic Inheritance

A

inheritance of conditions caused by mutation of a SINGLE gene
-has 2 laws (segregation and independent assortment)

44
Q

1st law

A

law of segregation
-pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete.
- Each parent passes a randomly selected gene copy to his/her offspring

45
Q

2nd law

A

law of independent assortment
-separate genes for separate traits are passed from parents to offspring independently of one another
-biological selection of one gene has nothing to do with the selection of the other gene

46
Q

What are some functions of the proteins encoded by genes that are related to hearing loss?

A

1) Cochlear fluid homeostasis
2) Ionic channels
3) Stereocilia morphology and function
4) Synaptic transmission
5) Gene regulation

47
Q

Most cases of genetic deafness recognized today are _____ disorders caused by mutation of ____ gene(s) and broadly classified by __________

A

1 ) Monogenic
2) Single
3) Mode of inheritance

48
Q

autosomal dominant (AD)

A

you only need one bad gene to show the phenotype
-the bad gene “overpowers” the good gene to cause an abnormal phenotype
-mom or dad can pass it down
-affected people are heterozygous

49
Q

autosomal dominant (AD) characteristics

A
  • 50 % risk to offspring per pregnancy
  • vertical transmission (each generation will have it)
    -unaffected individuals cannot transmit the disease
    -males and females are affected equally
    -variable expressivity and penetrance
50
Q

In autosomal dominance, what does expressivity refer to?

A

the severity of the genetic condition for the affected individuals
-how it expressed

51
Q

In autosomal dominance, what does penetrance refer to?

A

frequency of occurrence; expressed as a percentage
-some can manifest later in life
-some could appear to have skipped a generation because they are carriers

52
Q

What is D and d?

A

D=Dominant
d=recessive

53
Q

Dominant:
DD
Dd
dd

A

DD = homozygote (affected)
Dd = heterozygote (affected)
dd = homozygote (not affected)

54
Q

autosomal recessive

A

two identical copies of the bad gene are needed to show the phenotype

55
Q

Recessive:
RR
Rr
rr

A

RR = homozygous (hearing)
Rr = heterozygous (hearing/carrier)
rr = homozygous deaf

56
Q

characteristics of AR

A
  • 25% chance per pregnancy
  • obligate carrier (heterozygous); both parents have to be carriers for offspring to inherit
  • Horizontal pattern (same generation affected, but not others)
  • consanguinity is common
  • males and females affected equally
  • Founder effect
57
Q

what is the Founder effect?

A

Shared genetic ancestry/limited gene pool resulting in genetic conditions seen far more commonly in certain ethnic groups
ex. Tay Sach’s disease

58
Q

Complementary mating (AR)

A

Both parents carry a gene for a disorder, but the genes are different and don’t go together, so the kids don’t have the disorder.
- seen on a pedigree when both parents are affected but children are not

59
Q

non complementary mating (AR)

A

When both parents carry same gene for a disorder there kids will automatically get disorder
- seen on a pedigree when both parents are carriers and children end up affected

60
Q

psuedo dominance (AR)

A

inheritance of a recessive trait mimics a dominant pattern; one recessive allele could cause expression of the trait
- occurs in x-linked recessive inheritance of male offspring

61
Q

Examples of pseudo-dominance

A

-Hemophilia
-Color blindness

62
Q

X-linked recessive

A

If females are carriers with no sign of disease

63
Q

X-linked dominant

A

If females manifest some signs of the disorder

64
Q

X-Linked recessive characteristics

A
  • no male to male transmission
  • All daughters of a male with the trait will become carriers (men can only pass x to daughter) - 100%
  • Carrier daughters have a 50% chance to have abnormal sons, 50% chance for normal offspring, & a 50% chance of having a carrier daughter
65
Q

In an x-linked recessive (from mother) inheritance what happens if the son inherits bad x

A

even though it is recessive they don’t have a good X to balance out so they will automatically have the condition.

66
Q

X-linked dominant characteristics

A

if father is affected each female offspring 100% risk
If mother is affected 50% risk (she has two x’s to give)

67
Q

What are some examples of X-linked recessive inheritance?

A

1) Color blindness
2) Hemophilia
3) X-linked hearing loss with stapes gusher
4) Muscular dystrophy (Duchenne-type)

68
Q

What is the difference between X-linked recessive and X-linked dominant

A

If females are carriers with no sign of disease - X-linked recessive
If females manifest some signs of the disorder - X-linked dominant

69
Q

Hemizygous

A

men are neither heterozygous nor homozygous they only have a single X chromosome so they have only one copy of any gene on the X chromosome

70
Q

What is it called when a gene error in the X chromosome will cause disease in men because there is no corresponding paired X chromosome with a good gene to balance the bad gene making males affected?

A

Pseudo-dominance

71
Q

True or False: females are more severely affected than males in X-linked disorders

A

False

72
Q

in an X-linked dominant inheritance, what happens to the son if the father is affected?

A

The son should be unaffected because the father can only pass a Y down

73
Q

In a X-linked dominant inheritance, what happens to the daughter(s) if the father is affected

A

the daughter will be affected bc a father can only pass a daughter a X, and because it’s dominant it only needs one bad gene

74
Q

True or false: X-linked dominant is very common

A

False

75
Q

X-Linked Dominant Transmission Trait

A

-Chance of transmission from mother to son and daughter; both genders will be affected (50%)
-Transmission from affected father to daugher (100%)
-NO transmission from affected father to son

76
Q

Y-linked Inheritance

A

expressed only to male offspring because the father has to pass the Y to the son
- No father to daughter transmission
- abnormal male sexual devlopement

77
Q

Why are Y-linked traits only expressed to male offspring?

A

1) All males are hemizygous for all genes on the Y chromosome
2) No balancing of the mutant Y gene by X or another Y gene on the Y chromosome

78
Q

multifactorial inheritance

A

Traits as a result of multiple environmental factors with multiple genes
-Most commonly associated with sporadic gene mutations

79
Q

example of multifactorial inheritance

A

Oculo-Auricular Vertebral (OAV) spectrum disorder
-Consists of 3 rare disorders that may be intimately related to each other

80
Q

polygenic inheritance

A

traits or diseases caused by the impact of many different genes
-each gene has a small individual impact on the phenotype
-these traits are quantitative meaning the more genes involved, the more severe the manifestation will be
-example is cleft lip/palate

81
Q

Mitochondrial inheritance

A

the eve gene
- vertical pattern from mom
-no children of fathers with the trait will inherit it (0%)
-ALL children of an affected mother will be affected (100%)

82
Q

How to identify Mitochondrial inheritance

A

Looking at the pedigree you will see a vertical pattern (all generations will have it)
- Only mom if affected and ALL of her children will be affected

83
Q

why can’t men contribute in mitochondrial inheritance?

A

During meiosis the sperm sheds the mitochondria, so during fertilization the sperm as no cytoplasm so it has to come from the mother

84
Q

When should we suspect a mitochondrial disorder?

A

A wide variety of dysfunction in multiple organ systems should raise suspicions of a mitochondrial disorde

85
Q

True or false: mitochondrial DNA (mtDNA) has a slower spontaneous mutation rate than DNA in nuclear genes

A

FALSE: it is higher because mtDNA evolves 5 to 10 times more rapidly than genomic DNA

86
Q

Examples of mitochondrial inheritance

A

Leber’s hereditary optic neuropathy
- sudden loss of central vision and optic nerve damaged at20 years of age

87
Q

Genomic Imprinting

A

process in which the phenotype differs depending upon which parent transmits a particular allele or chromosome
-phenotype will vary based on if it’s from mom or dad
-it is the same gene mutation but will result in a different phenotype

88
Q

Example of Genomic Imprinting

A

deletion of chromosome 15 will result in prader willi syndrome (paternal origin) and angelman syndrome (maternal)

89
Q

anticipation

A

due to allelic expansion, severity will get worse
-worsening of symptoms of a genetic disease from one generation to the next

90
Q

allelic expansion

A

Increase in gene size
-Caused by an increase in the number of tyrinucleotide base sequences

91
Q

what are examples of allelic expansion and anticipation

A

huntington’s disease (AD pattern)
-gene on tip of chromosome 4p
normal: has 6-37 copies
affected: has 35-121 copies

92
Q

consanguinity is an issue in _____ transmission and NOT an issue in ____

A

AR, AD

93
Q

If there are carriers involved it is NOT a _____ transmission

A

AD

94
Q

why are y-linked patterns rare?

A

the y chromosome is the smallest chromosome with a small amount of genes

95
Q

if you see carriers on a pedigree, what does this indicate right away?

A

it is a recessive type of inheritance
-it CANNOT be AD

96
Q

what is an important characteristic about chromosomal abnormalities?

A

they affect multiple systems

97
Q

X-linked dominant vs autosomal dominant

A

in an x-linked dominant there is NO father to son transmission, AD can be passed from all parents to offspring

5310 - Embryology (11 decks)

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