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Genetic Disorders Part 2 Flashcards

1
Q

what are complex multigenic disorders

A
  • multifactorial or polygenic disorders

- variant gene + environmental factors

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2
Q

examples of complex multigenic disorders

A
  • diabetes mellitus type 2
  • congential heart disease
  • cleft lip
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3
Q

what do you exclude when diagnosing multifactoral or polygenic disorders

A
  • exclude Mendelian disorder

- exclude chromosomal mode of inheritance

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4
Q

what is a karyotype

A
  • cells in metaphase

- chromosomes are arranged in decreasing length

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5
Q

when stain is used for katyotype

A
  • Giemsa stain = G banding

- gives you light and dark bands

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6
Q

normal human chromosome #

A

46
(2n=46)
n= 23

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7
Q

what is euploid

A

2n

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8
Q

what is polyploid

A

3n

4n

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9
Q

what is aneuploid

A

not an exact number of n

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10
Q

what are cytogenetic disorders

A
  • spontaneous abortions (50% due to chromosome abnormality)

- change in # and structure of chromosomes

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11
Q

which chromosomes do cytogenetic disorders affect

A

autosomes and sex chromosomes

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12
Q

what are the types of chromosomal rearrangements

A
  1. translocation (reciprocal/ balanced. Robertsonian)
  2. deletion
  3. isochromosome
  4. inversion
  5. ring chromsome
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13
Q

what is mosaicism

A

same individual 2 or more population of cells

  • different complements of chromosomes
  • mosaicism is common in sex chromosomes
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14
Q

what are the cytogenetic disorders involving autosomes

A 
trisomy 21 (Down Syndrome)
22q11.2 Deletion Syndrome
Trisomy 18 (Edwards Syndrome)
Trisomy 13 (Patau Syndrome)
Deletion 5p (Cri du chat Syndrome)
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15
Q

karyotype of trisomy 21

A

21:47XX, +21 (95%)

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16
Q

what is the translocation type of trisomy 21

A

46XX der (14;21)(q10:q10) + 21 (4%)

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17
Q

what is the mosaic of trisomy 21

A

46XX/47XX, +21 (1%)

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18
Q

what are the 2 candidate genes for trisomy 21 (chromosome 21)

A

DYRK1A codes for a serine-threonine kinase

RCAN1 regulator of calcineurin 1

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19
Q

characteristics of Trisomy 21

A
  • epicanthic folds, flat facial profile
  • redundant neck skin; Simian crease
  • mental retardation
  • congenital heart disease (VSD, ASD)
  • acute leukemia (ALL, AML)
  • intestinal stenosis, umbilical hernia
  • Alzheimer disease
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20
Q

characteristics of Trisomy 18 (Edward Syndrome)

A
  • prominent occiput
  • mental retardation
  • micrognathia
  • clenched fist
  • IUGR (intrauterine growth retardation)
  • polyhydramnios
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21
Q

characteristics of Trisomy 13 (Patau Syndrome)

A 
Microcephaly
Mental retardation
Cleft lip
Cleft palate
Polydactyly –extra digits
Cardiac defects –mostly VSD
Renal defects
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22
Q

what is 22q11 Deletion syndrome

A

intestinal deletion: 22q11.2

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23
Q

what 2 previous diseases were 22q11 Deletion Syndrome

A 
DiGeorge syndrome
Velocardiofacial syndrome (VCFS)
24
Q

what is DiGeorge syndrome

A

T cell immunity, hypocalcemia

25
what is VCFS
dysmorphology, cardiac defects
26
22q11 Deletion Syndrome can causes
Schizophrenia
27
what is CATCH 22
``` Cardiac defects Abnormal face T cell immunity abnormal/Thymic hypoplasia Cleft palate Hypocalcemia 22q11 deletion ```
28
what is Del (5p) Cri du chat
terminal deletion of chromosome 5
29
characteristics of Del (5p) Cri du chat
"cat-like" cry laryngeal hypoplasia microcephaly mental retardation
30
what are 2 cytogenetic disorders involving sex chromosomes
1. Klinefelter syndrome | 2. Turner syndrome
31
what is the karyotype of Klinefelter syndrome
XXY
32
what is the mosaic pattern of Klinefelter Syndrome
46,XY/47, XXY, 47,XXy/48,XXXY
33
Klinefelter syndrome results in
male hypogonadism - testicular atrophy - impaired spermatogenesis - reduced hair - low serum testosterone
34
Klinefelter syndrome increases the frequency of obtaining
Breast cancer SLE Extragonadal germ cell tumor Leydig Cell Tumor
35
what are the single-gene disorders with atypical patterns of inheritance
1. Triplet repeat mutations 2. mutations in mitchondrial genes 3. alteration of imprinted regions of genome
36
name an example of triplet repeat mutations
Fragile X syndrome | Xq27.3
37
what gene is mutated in Fragile X syndrome
FMR1 gene mutation
38
Fragile X syndrome has an amplification of
CGG repeat | -amplification during oogenesis
39
Fragile X syndrome
normal: 29 CGG premutation: 55 to 200 Oogenesis = CGG expansion Full mutation: greater than 200 repeats
40
Fragile X syndrome: carrier males transmit
- normal males - phenotypically normal * grandchildren are affected - at risk for FX Tremor Ataxia syndrome (FXTAS)
41
Fragile X syndrome carrier females
30%-50% are affected | -primary ovarian failure
42
Fragile X syndrome anticipation
manifestations worsen with successive generations
43
what can cause Fragile X Syndrome
Neurodegenerative manifestation Ataxia Macroorchidism Abnormal facial features
44
how do mutations in mitochondrial genes occur
1. mitochondrial DNA - maternal inheritance - transmitted to all offspring 2. daughters transmit DNA to progeny 3. sons do not transmit the DNA 4. phenotypic variation
45
where is mitochondrial DNA
- Brian, ovary, skeletal muscles - oxidative phosphorylation - electron transport chain
46
what is Leber hereditary optic atrophy (LHON)
- prototype disorder - transmitted though mother - mitochondrial NADH dehydrogenase 1 (MT-ND1) - causes oxidative phosphorylation - loss of vision
47
what diseases caused by alterations of imprinted genes
1. Prader-Willi Syndrome | 2. Angelman Syndrome
48
what is genomic imprinting
- an epigenetic process (not a mutation!) - differential inactivation - paternal genes - materal genes
49
how does genomic imprinting occur
- methylation of the gene promotor - modifications of DNA binding proteins - silencing of the gene - maternal imprinting - paternal imprinting
50
what gene is deleted in Prader-Willi Syndrome
-interstitial deletion of 15q12
51
Prader-Willi Syndrome affects
paternal chromosome
52
characteristics of Prader-Willi Syndrome
short stature, small hands, feet; hypogonadism
53
what gene is deleted in Angelman Syndrome
interstitial deletion of 15q12
54
what happens to the maternal chromosome in Angelman Synrome
maternal chromosome is silenced
55
characteristics of Angelman Syndrome
-mental retardation, ataxia, inappropriate laughter
56
what is the Angelman gene
-maternally derived | UBE3A - a ligase in ubiquitin-proteosom proteolytic pathway

Pathology (18 decks)

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