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AUDE 5310 Embryology & Genetic Conditions > Chromosomal Disorders (Congenital Monogenetic HL) > Flashcards

Chromosomal Disorders (Congenital Monogenetic HL) Flashcards

1
Q

what is cytogenetics

A

branch of genetics that studies structure and function of the cell, especially chromosomes

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2
Q

what is a characteristic of chromosomal abnormalities?

A

intellectual disabilities
abnormal growth patterns & multiple systems involved

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3
Q

what is aneuploidy

A

numerical aberration of whole chromosome

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4
Q

only ____ autosomal trisomies and ___ sex trisomy can survive

A

3, 1

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5
Q

what are the trisomies that are survivable

A

13, 18, 21, X

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6
Q

why do we think that with advanced maternal age you run the risk of trisomies? (oogenesis)

A

amount of time the egg spends in the diplotene stage
egg doesn’t complete meiosis stage until fertilization
by time is age is older, the egg has been in diplotene stage for this long

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7
Q

what causes an increase in incidence of chromosomal trisomies

A

advanced maternal age

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8
Q

what is trisomy 13

A

Patau syndrome

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9
Q

what are the clinical findings of trisomy 13

A

patau syndrome
brain, heart, difficulty breathing, cleft lip/palate vision problems, extra digits, deformed tectorial membrane - why they dont worry about hearing

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10
Q

rare chromosomal disorder and generally exhibits the most severe birth defects

A

trisomy 13, Patau syndrome

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11
Q

what are the audiological findings in Patau syndrome

A

abnormal helices
low set ear
most show severe to profound bilateral SNHL or deafness

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12
Q

what is trisomy 18

A

edwards syndrome

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13
Q

all trisomies have

A

heart defects, low infertility, intellectual abilities

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14
Q

what are the clinical findings of edwards syndrome

A

profound intellectual disability with seizures
clenched hands with overlapping fingers
high arched palate & small mouth
heart defects

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15
Q

audiologic findings in Edwards syndrome

A

malformed & low set pinnae
most probably severe HL or deaf

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16
Q

___ fetus have higher rates of miscarriage

A

males

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17
Q

what is the most common chromosome defect in humans

A

trisomy 21

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18
Q

what is trisomy 21

A

down syndrome

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19
Q

only ____ of Down’s are born, _____ are fatal

A

30%, 70%

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20
Q

why are people with downs living longer now

A

advancements in medicine, better able to understand what is going on and how to treat them

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21
Q

The incidence of births of children with Down syndrome increases with

A

the age of the mother

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22
Q

what are clinical features in down syndrome

A

flat face (zygomatic bone) and long tongue and short limbs
hypotonia - poor muscle tonew

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23
Q

audiologic findings of trisomy 21

A

low set pinna
stenoic ear canals, middle and inner ear defects
HL can be conductive, mixed, or snhl

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24
Q

what is stenosis

A

small ear canal

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25
HL in 60% of cases with downs is
secondary to serious otitis media and impacted cermen in stenoic ear canals
26
what is microglossia and where is it seen
tongue doesn't fit into the mouth, abnormal smallness of the tongue down's
27
is edwards syndrome mostly male or female
female, males usually higher rates of miscarriage
28
what percentage is robertsonian translocation in down's?
around 4%
29
features of robertsonian translocation in seen in
acrocentric chromosomes (13, 14, 15, 21, 22)
30
An acrocentric centromere partitions the chromosome into
long arm containing vast majority of genes and short arm with smaller proportion of genetic content
31
what happens during robertsonian translocation
participating chromosomes break at their centromeres and long arms fuse to form single chromosome with single centromere short arms join together to form another product which contains nonessential genes and is usually lost within a few cell divisions
32
long arms coming together of the acrocentric chromosomes
robertsonian translocation
33
If RT joins long arm of chromosome 21 with long arm of chromosome 14 (or 15),
heterozygous carrier is phenotypically normal or balanced
34
unbalanced trisomy 21
causes down syndrome
35
balanced trisomy 21
normal
36
RT carrying 14 & 21 + extra chromosome 14 =
normal phenotype and heterozygous
37
Mom Carrier of RT - risk of 2nd trisomy 21 pregnancy =
10-15%
38
Dad carrier of RT -
risk is <2%
39
An offspring of RT carrier can inherit
unbalanced or balanced forms of trisomy 21
40
RT carrying 14 & 21 + extra chromosome 21 =
Down Syndrome
41
what is mosaicism
two or more cell lines (cell populations) that differ genetically in an individual or tissue but that are derived from a single zygote
42
Mosaicism in single genes can be either
somatic or germ cells
43
what does mosaicism explain in rare AD conditions in offspring whose parents are phenotypically normal
achondroplasia, hemophilia, some bone diseases
44
sex chromosome mosaicism conditions
mosaic klinefelter syndrom mosaic turner syndrome
45
if the parents are normal how can you have dominant condition?
spontaneous condition
46
what is achondroplasia
dwarfism
47
what is another name for x inactivation
lyonization
48
what is x inactivation
form of germ cell mosaicism
49
females inherit ____ as many X chromosomes as males
twice
50
what does x inactivation do for females
prevents females from having twice as many x chromosome gene products as males all women are mosaics we have 2 x chromosomes and men have xy if both x remained active, we would have too many genes one x is inactivated (random)
51
once inactivated will it remain inactivated thorughout the lifetime of the cell
yes
52
what happens if some of inactivated x genes are still expressing
only happens in women which is why autoimmune disorders mostly affect women these genes create proteins that should not be there
53
is x inactivation variable
yes
54
What is a barr body
random inactivated x that shows up as a darkened condensed chromosomal region in the cell
55
females are a mix of
mix of Xm and Xp
56
what are 3 ways down's can be inherited
trisomy 21 (nondisjunction) translocation mosaicism
57
what % is nondisjunction
around 95% of cases
58
what % is translocation
approx 4% of cases
59
what % is mosaicism
around 1% of cases
60
what is nondisjunction trisomy 21
prior or at conception, pair of 21 chromosomes in either sperm or egg fails to separate as embryo develops extra chromosome is replicated in every cell of the body and accounts for an extra chromosome 21
61
what is translocation in trisomy 21
part of chromosome 21 breaks off during cell division and attaches to another chromosome (usually chrom 14) total number of chromosomes in cells remain 46 but presence of an extra part of chromosome 21 causes the phenotype of down syndrome
62
what is mosaicism
occrus when nondisjunction of chromosome 21 takes place in one but not all the initial cell divisions after fertilization when this happens mixture of two types of cells occur with usual 46 chromosomes and others containing 47 (containing the extra 21)
63
individuals with mosaic downs have
could have fewer characteristics of downs but it is difficult to broadly generalize due to variability of the condition
64
does mosaicism take place in multiple cells
no only one
65
what is a ring chromosome
rare genetic condition caused by having an abnormal chromosome that forms a ring when ring forms both arms break and broken 'sticky' ends fuse at the breakage points broken fragments are lost and any genes that were on them
66
can chromosomes happen on any chromosome
yes
67
what are the most common ring chromosomes
the acrocentric ones r13, r14, r15, r21, r22
68
how are majority of ring chromosomes inherited
99% from sporadic mutatiosn
69
can ring chromosomes be inherited
yes approx 90% are from mother ring chromosomes associated with reduced fertility in men
70
ring chromosomes have effects on
cell growth
71
what can happen to a ring chromosome during cell division
may become entangled broken double in size
72
what is mosaicism
resulting cells that arise with the wrong amount of chromosome material (too much or too little)
73
what is chimerism
can manifest as the presence of two sets of DNA or organs that do not match dna of the rest of the organism
74
what is often the result of chimerism
two non-identical twin embryos merging together instead of growing on their own
75
what are characteristics of chimerism
hermaphroditic, have both males and female sex organs
76
can chimerism have different patches of dna thorughout the body
yes
77
what is the karyotype of turner syndrome
45 X0
78
which x is absent in 80% of cases
paternal x
79
what are the clinical features of turner syndrome
short stature and thick/web neck wide chest and streak gonads iq slightly below normal
80
what is turner syndrome
condition where x linked recessive trait may express phenotypically in females because only one x chromosome is present
81
what is a streak gonad
immature gonads infertile
82
what are the audiologic findings of turner syndrome
low set protruding pinna and narrow ear canals recurrent ear infections and chronic otitis media
83
long term consequences of ear infections?
speech and language development delays
84
how do babies learn language
incidental learni g
85
x linked recessive - will a female show phenotype of turner syndrom?
no because the other x will balance itout
86
what is the phenotype of turner syndrome
they look like females
87
what is the single most common cause of male infertility?
klinefelter's syndrome
88
what is klinefelter's syndrome
47, xxy they have two XX and a Y extra sex chromosome phenotype is a male because of the Y
89
47 xxy
klinefelter syndrome
90
what are the clinical features
tall and thin with disproportionately long legs development normal until puberty poor attention and judgment behavior and psychosocial problem
91
what are the audiological features of Klinefelter's syndrome
SNHL in cases reported with poor auditory discrimination and delayed speech development

AUDE 5310 Embryology & Genetic Conditions (18 decks)

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