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5310 - Embryology > Syndromic Hearing Loss and Deafness > Flashcards

Syndromic Hearing Loss and Deafness Flashcards

1
Q

Importance of epidemiology

A

to study the effect on society and determine what measures to take at a governmental or state level
ex. Covid;

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2
Q

Syndromic

A

multiple systems

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3
Q

nonsyndromic

A

one condition

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4
Q

How many babies are born with genetic/birth defects

A

1 in every 33

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5
Q

Epidemiology

A

looking at population outcomes
- study of how diseases spread and why they affect some groups more than others.

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6
Q

Incidence of HL

A

looking at new cases of defects
- how many over time

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7
Q

prevalence of HL

A

the existing # of cases

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8
Q

ways to reduce birth defects

A
  • 400 micrograms of folic acid daily
  • up to date on immunizations
  • avoid tobacco, smoke, drugs, alcohol
  • insect bites
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9
Q

what is the most common sensory deficit in humans

A

hearing loss

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10
Q

HL is ____ in women and _____ in men

A

lower, higher

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11
Q

Black’s have _____ HL than white people

A

less

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12
Q

monogenic

A

single gene mutation
ex. A replaced for G

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13
Q

Complex or Multifactorial Inheritance

A

causes of HL include genetic & environmental factors acting independently & together
- Ex. certain ototoxic medications can contribute to HL in individuals with a genetic predisposition.

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14
Q

What ways does the environment (non genetic) lead to pre-lingual deafness

A
  • Infections
  • Extreme prematurity
  • Ototoxicity
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15
Q

Gene mapping

A

the approximate or exact location of a gene on a chromosome
-chromosome,arm,band,region

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16
Q

Gene cloning

A

production of exact copies of a gene or DNA sequence

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17
Q

Syndromic loci

A

disorders show abnormalities in many areas

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18
Q

Nonsyndromic loci

A

nonsyndromic disorders are not associated with another other symptoms or disorders

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19
Q

DFN

A

deafness neurosensory

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20
Q

DFNA

A

autosomal dominant deafness neurosensory

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21
Q

DFNB

A

autosomal recessive deafness neurosensory

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22
Q

DFNX

A

X linked recessive deafness neurosensory

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23
Q

DFNY

A

Y linked deafness neurosensory

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24
Q

DFMN

A

modifer deafness neurosensory

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25
Q

AUNA

A

auditory neuropathy deafness neurosensory

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26
Q

OTSC

A

otosclerosis

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27
Q

modifer gene

A

type of gene that alters the expression or effect of other genes.
-Instead of directly causing a particular trait or characteristic, modifier genes influence the outcome or severity of traits controlled by other genes.

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28
Q

pleiotropy

A

when one gene influences two or more seemingly unrelated phenotypic traits.
- when ONE gene exhibits multiple phenotypic expressions
- ex.Marfan’s Syndrome

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29
Q

Homeostasis

A

the ability of an organism or a cell to maintain internal equilibrium by adjusting its physiological processes

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30
Q

Inner ear homeostasis

A

ionic balance of perilymph and endolymph within the ear

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31
Q

what is needed for proper inner ear function?

A

a tight control on the ion movement across the cell membranes is necessary
- Hair cell functions
- Regulation of extracellular endolymph and perilymph
- Conduction of nerve impulses

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32
Q

The major ions involved in inner ear homeostasis are _____ &______. ______ & ______ also play a significant role.

A
  • sodium (NA +), potassium (K+)
  • chloride (Cl-), calcium (CA2+)
33
Q

Disorders of cochlear HL & vestibular dysfunction are caused by_____.

A

disruption of ion homeostasis

34
Q

what causes disorders of ion homeostasis

A

disruption of the strial ion transport mechanism is the final pathway

35
Q

What is the majority of non-syndromic HL due to?

A

the alteration of proteins that prevent movement of potassium from the organ of corti to the lateral wall and into the stria

36
Q

what are the two disorders of ion homeostasis

A
  • endolymphatic hydrops
  • endolypmphatic xerosis
37
Q

endolymphatic hydrops

A

increased potassium transport in the endolymph or increased endolymph production
-Ex. meniere’s disease

38
Q

endolypmphatic xerosis

A

decreased potassium transport in the endolymph or decreased endolymph production
- related to connexin (causing HL in humans)

39
Q

endolypmphatic xerosis is belived to be the cause of ?

A

hearing loss in humans
- Connexin 26
- absence of KCNE1 & KCNQ1

40
Q

how do we classify genetic deafness and hearing loss?

A
  • chromosome disorders
  • external ear changes (treacher collins, BOR)
  • eye disease (ushers, norrie)
  • musculoskeletal disease (crouzon, stickler)
  • renal disease (alport)
  • cardiac system disease (jervell lange nielsen
  • neurologic (friedreich ataxia)
  • endocrine (pendred)
  • metabolic
  • integumentary (waardenburg)
41
Q

cytogenetics

A

studies the cell, primarily the chromosome, structures and functions
-looking at the number and structure

42
Q

chromosomal vs. single gene

A

whole body vs. system

43
Q

Aneuploidy

A

abnormality in the number of chromosomes in a cell, where the whole chromosome is affected rather than just a segment of it.

44
Q

what is a characteristic of chromosomal abnormalities?

A
  • intellectual disabilities
  • abnormal growth patterns & multiple systems involved
45
Q

monosomy

A

the presence of only one copy of a particular chromosome in a cell, instead of the usual two copies.

46
Q

trisomy

A

the presence of an extra copy of a chromosome in a cell, resulting in a total of three copies of that chromosome instead of the usual two

47
Q

monosomy vs trisomy in terns of life expectancy

A
  • monosomy lethal
  • trisomy SOME are livable
48
Q

what is the monosomy exception?

A

the loss of a sex chromosome can result in a live birth

49
Q

what are the 3 autosomal trisomies and 1 sex trisomy that can survive to term?

A

13, 18, 21, & X
- x is a subcategory of 21

50
Q

Trisomy 13

A

Patau Syndrome
- short life span
- intellectual disability, blindness (coloboma’s- missing pieces of tissue), cleft lip, heart defects and extra toes/fingers

51
Q

audiological findings of trisomy 13

A
  • abnormal helices
  • low-set ear
  • most children show a severe to profound bilateral SNHL or deafness
52
Q

trisomy 18

A

Edwards syndrome
- extra chromosome 18
-short life span, majority will die within 1st year
-intellectual disability, seizures, small mouth with arched palate, small lower jaw, clenched hands and heart defects

53
Q

trisomy 18 audiological findings

A
  • malformed and low set pinna
  • abnormal ME/IE
  • severe HL or deafness
54
Q

what is the most common chromosome defect in humans

A

trisomy 21 (down syndrome)

55
Q

trisomy 21

A

down syndrome
- intellectual disability
- IQ decrease with age
- flattened facial features
- large tongue
- short limbs
- poor muscle tone
- heart disease

56
Q

trisomy 21 audiological findings

A

low set pinna
narrow ear canal
- conductive, SNHL, or Mixed

57
Q

Of the human trisomies which exhibits the most serve birth defects?

A

trisomy 13

58
Q

what are the 3 ways down syndrome is inherited

A
  1. nondisjunction
  2. robertsonian translocation
  3. mosaicism (x-inactivation):
    - only 1% very rare
59
Q

nondisjunction inheritance

A

a pair of 21 chromosomes fails to separate in either the egg or sperm and as the embryo develops the extra chromosome is replicated in every cell of the body

60
Q

robertsonian translocation

A
  • the chromosome breaks at its centromere & the long arm fuses to form a single chromosome with a single centromere.
  • the short arms will fuse together & are usually lost
61
Q

mosaicism

A

an individual has two or more populations of cells with different genetic makeup within their body derived from a single zygote

62
Q

what does mosaicism explain in rare autosomal dominant conditions in offspring when the parents are phenotypically normal

A

unusual clinical observations such as:
Somatic: achondroplasia (dwarfism), hemophilia, some bone diseases
Sex: klinefelter & turner syndrome

63
Q

what is the germ cell mosaicism

A

X-inactivation

64
Q

x-inactivation

A
  • only happens in women
    prevents females from having twice as many x chromosomes as males
    -since females get two x’s, one at random will be turned off
65
Q

how does x-inactivation cause down syndrome

A

some of the inactivated genes are actually expressing creating a mosaic

66
Q

ring chromosome

A

occurs when an abnormal chromosome forms a ring structure
- one chromosome usually intact the other forms ring

67
Q

how does a ring chromosome form

A

both ends of a chromosomes break and the broken ends fuse at the breakage points
- broken pieces are lost & any genes they contain
- like breaking a stick and gluing the ends together it will never be perfect again

68
Q

what chromosomes do ring chromosomes occur in ?

A

any chromosome but more commonly acrocentric chromosomes
- r13, r14, r15, r21, r22

69
Q

chimerism

A

the presence of two sets of DNA or organisms that do not match the DNA of the rest of the organisms

70
Q

what happens with chimerism

A

two non-identical twin embryos merging together instead of growing on their own
- Hermaphroditic: male and female sex organs

71
Q

turner syndrome

A

genetic condition where females are born with only one X chromosome
- because there is only one X chromosome present, any recessive traits carried on the X chromosome will be expressed phenotypically in females, even though they are recessive.

72
Q

characteristics of turner syndrome

A
  • short stature with thick or webbed neck
  • immature gonads (infertility)
    -IQ slightly below normal
73
Q

what is the karyotype of turner syndrome

A

45,X0

74
Q

audiological findings of turner syndrome

A
  • low set pinna, narrow ear canal
  • recurrent ear infections and OM
75
Q

klinefelter’s syndrome

A

occurs when a male is born with an extra X chromosome, resulting in a karyotype of 47,XXY instead of the typical 47,XY.

76
Q

klinefelter’s syndrome characteristics

A

-tall/thin with long legs
-hypogonadism around puberty with extra breast tissue
-male gonads but they are not functional
-IQ in low to normal range
-behavioral and psychosocial problems

77
Q

klinefelter’s syndrome audiological findings

A
  • SNHL
  • discrimination & delayed speech development
78
Q

are turner and klinefelter inherited conditions or spontaneous mutations?

A

spontaneous mutations

5310 - Embryology (11 decks)

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