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Robbins Pathology > CHAPTER 5 > Flashcards

CHAPTER 5 Flashcards

1
Q

What are the most important genes implicated in Type I DM?

A

6 or 7

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2
Q

How many chromosomes do human somatic cells contain?

A

46 chromosomes (22 pairs autosomes, 2 sex chromosomes)

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3
Q

__________ is the study of chromosomes

A

karyotyping

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4
Q

What is the usual procedure to examine chromosomes?

A

Arrest dividing cells in metaphase

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4
Q

Example of mitotic spindle inhibitors use to arrest dividing cells for chromosome examination?

A

N-diacetyl-N-methylcolchicine [colcemid]

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5
Q

How many bands can be detected in one haploid set?

A

Approximately 400-800 bands

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6
Q

Any exact multiple of the haploid number of chromosomes (23) is called ____________

A

Euploidy

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7
Q

______________ refers to an error occurs in meiosis or mitosis and a cell acquires a chromosome complement that is not an exact multiple of
23

A

aneuploidy

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8
Q

What are the usual causes of aneuploidy?

A

Nondisjunction and anaphase lag

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9
Q

This cause of aneuploidy occurs during gametogenesis, wherein the gametes formed have either an extra chromosome (n + 1) or one less chromosome (n − 1)

A

Nondisjunction

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10
Q

This cause of aneuploidy occurs when one homologous chromosome in meiosis or one chromatid in mitosis lags behind and is left out of the cell nucleus.

A

Anaphase lag

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11
Q

Mitotic errors in early development give
rise to two or more populations of cells with different chromosomal complement in the same individual.

A

mosaicism

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12
Q

Mitotic errors in mosaicism happens during ________

A

Cleavage of the fertilized ovum or in somatic cells.

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13
Q

refers to the loss of a portion of a chromosome

A

deletion

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14
Q
A
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14
Q
A
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15
Q

Occurs when there
are two breaks within a chromosome arm, followed by loss of the chromosomal material between the breaks and fusion
of the broken ends.

A

Interstitial deletion

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16
Q

result from a
single break in a chromosome arm, producing a fragment
with no centromere, which is then lost at the next cell
division

A

Terminal deletions

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17
Q

When a break occurs at both ends of a chromosome with fusion of the damaged ends

A

Ring Chromosome

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18
Q

Refers to a rearrangement that involves two
breaks within a single chromosome with reincorporation
of the inverted, intervening segment

A

Inversion

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19
Q

a segment of one chromosome is transferred to another

A

Translocation

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19
Q

Is a form of translocation where there are single breaks in each of two chromosomes, with exchange of material

A

Balanced reciprocal translocation

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20
Q

A translocation between two acrocentric chromosomes typically the occurring close to the centromeres of each chromosome.

A

Robertsonian translocation

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21
Q

True or false: individuals with robertsonian translocation are phenotypically normal

A

True

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22
Q

The most common of the chromosomal disorders and is a major cause of intellectual disability.

A

Down Syndrome (Trisomy 21)

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23
Q

What is the most common cause of trisomy 21?

A

meiotic nondisjunction

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24
Q

What type of genetic aberration occurs in about 4% of patients with trisomy 21?

A

Robertsonian Translocation of the long arm of chromosome 21 to another acrocentric chromosome (22, 14)

25
Q

What type of genetic aberration occurs in about 1% of patients with trisomy 21 resulting in mosaicism?

A

mitotic nondisjunction of chromosome 21 during an early stage of embryogenesis

26
Q

What is the most frequent forms of congenital heart diseases in Down syndrome in about 43% of cases?

A

atrioventricular septal defects

27
Q

What are the risks of developing leukemias in individuals with Down Syndrome?

A

20-fold acute B lymphoblastic leukemia

500-fold acute myeloid leukemia (acute megakaryoblastic leukemia)

28
Q

What is the protein that is overexpressed in chromosome 21 that is responsible in early onset Alzheimer’s disease in Down Syndrome?

A

Amyloid-beta precursor protein

29
Q

What are the karyotypes of Down Syndrome?

A

Trisomy 21 type: 47,XX, +21

Translocation type: 46,XX,der(14;21)(q10;q10),+21

Mosaic type: 46,XX/47,XX, +21

30
Q

What are the karyotypes of Edwards Syndrome?

A

Trisomy 18 type: 47,XX, +18

Mosaic type: 46,XX/47,XX, +18

31
Q

What are the karyotypes of Patau Syndrome?

A

Trisomy 13 type: 47,XX, +13

Translocation type: 46,XX,+13,der(13;14)(q10;q10)

Mosaic type: 46,XX/47,XX, +13

32
Q

This trisomy presents with the following features: prominent occiput, intellectual disability, micrognathia, low set ears, short neck, overlapping fingers, congenital heart disease, renal malformations, rocker-bottom feet

A

Trisomy 18 (Edwards Syndrome)

33
Q

This trisomy presents with the following features: microcephaly, intellectual disability, microphthalmia, polydactyly, cleft-lip and palate, cardiac defects, umbilical hernia, renal defects, rocker-bottom feet

A

Trisomy 13 (Patau Syndrome)

34
Q

Chromosome 22q11.2 presenting with thymic hypoplasia, parathyroid hypoplasia, cardiac malformation and mild facial anomalies, atopic disorders, and autoimmunity.

A

DiGeorge Syndrome

34
Q

This trisomy presents with the following features: epicanthal folds, flat facial profile, intellectual disability, abundant neck skin, congenital heart defects, intestinal stenosis, umbilical hernia, hypotonia, gap between first and second toe.

A

Trisomy 21 (Down Syndrome)

35
Q

Chromosome 22q11.2 presenting with facial dysmorphism (prominent nose, retrognathia), cleft palate, cardiovascular anomalies, learning disabilities and rarely immunodeficiency

A

Velocardiofacial

36
Q

What the mapped genes closely associated with chromosome 22q11.2 deletion syndrome?

A

TBX1 and T-box transcription factor

37
Q

Where do the genes closely associated with chromosome 22q11.2 deletion syndrome are expressed?

A

Pharyngeal mesenchyme and endodermal pouch

38
Q

What is the gene involved in X chromosome inactivation?

A

XIST

39
Q

inactive X chromosome seen in interphase nucleus

A

Barr bodies

40
Q

How does XIST allele silence X chromosome?

A

By coating the X chromosome and initiating gene-silencing process by chromatin modification and DNA methylation

41
Q

What is the gene that determines testicular development?

A

SRY

42
Q

Deletion involving the Y chromosome results in what condition?

A

azoospermia

43
Q

What are the two major factors of Klinefelter syndrome?

A
  1. aneuploidy and the impact of increased gene dosage by the supernumerary X
  2. hypogonadism
44
Q

What are the characteristics of Klinefelter syndrome?

A

Eunuchoid body habitus
Abnormally long legs
Small atrophic testes
Small penis
Lack of secondary male characteristics
gynecomastia
Average or below average intellect
Modest deficit in verbal skills

45
Q

Individuals with Klinefelter syndrome are at a higher risk of developing what type of heart disease?

A

Mitral Valve Prolapse

46
Q

What type of extragonadal germ cell tumors are individuals with Klinefeilter syndrome at risk of developing in a 20-30 folds?

A

Mediastinal teratoma

47
Q

What are the hormonal aberration in individuals with Klienfelter syndrome?

A

Elevated Follicle Stimulation Hormone and Estrogen, decreased testosterone

48
Q

What gene maps on the pseudoautosomal region of Xp is one of the genes that is not subject to X
inactivation and is probably responsible for the tall stature and long legs typical of Klinefelter syndrome and haploinsufficiency leads to short stature in individuals with turner syndrome?

A

Short-stature
HomeobOX (SHOX) gene

49
Q

This condition results from complete or partial
monosomy of the X chromosome and is characterized by hypogonadism in phenotypic females

A

Turner syndrome

50
Q

What are the karyotype seen in Turner syndrome?

A

45,X
Isochromosome 46,X,i(X)(q10)
ring chromosome 46,X,r(X)
Deletion of portions of the short or long arm, 46X,del(Xq), or 46X,del(Xp)

51
Q

What are the congenital heart disease features seen in turner syndrome?

A

Preductal coarctation of the aorta and bicuspid aortic valve

52
Q

What are the characteristic features of individuals with turner syndrome?

A

lymph stasis –> neck webbing –> cystic hygroma

Failure to develop secondary sex characteristics
Genitalia remain infantile
Breast development is inadequate
Little pubic hair
Short stature
Amenorrhea
Normal mental status but may have subtle defects in nonverbal, visual-spatial information

53
Q

What are the areas of action of SHOX gene?

A

radius, ulna, tibia, and fibula, expressed in the first and second pharyngeal arches

54
Q

What are the examples of Trinucleotide-Repeat Mutations Affecting Non-coding Regions?

A

Fragile X syndrome (FMRI Gene:FMR-I Protein)
Friedreich Ataxia (FXN:Frataxin)
Myotonic Dystrophy (DMPK:Myotonic Dystrophy Protein Kinase)

55
Q

What are the mechanisms by which unstable repeats cause diseases?

A
  1. Loss of function of the affected gene, typically by transcription silencing
  2. A toxic gain of function by alterations of
    protein structure
  3. A toxic gain of function
    mediated by RNA
56
Q

What gene and protein is affected in Fragile X Syndrome?

A

familial mental retardation 1 (FMR1) gene:FMR-I Protein; tandem repeats of CGG

57
Q

The cytogenetic alteration
was discovered as a discontinuity of staining or as a constriction
in the long arm of the X chromosome when cells are cultured in a folate-deficient medium and was later supplanted by DNA-based analysis of triplet repeat
size.

A

Fragile X Syndrome

58
Q

What are the features of Fragile X Syndrome in male individuals?

A

marked intellectual disability
long face with a large mandible
large everted ears
large testicles (macro-orchidism) - most distinct features
Hyperextensible joints
high arched palate
mitral valve prolapse

59
Q

What are the characteristics of carrier females with Fragile X associated Primary Ovarian Failure?

A

Premature ovarian failure before the age 40
Menstrual irregularities
Decreased fertility
Elevated FSH and decreased antimullerian hormone

60
Q

What are the characteristics of a transmitting male with FX-associated tremor/ataxia syndrome?

A

Progressive neurodegenerative syndrome in 6th decade
Intention tremors
Cerebellar ataxia
May progress to parkinsonism

61
Q
A

Robbins Pathology (2 decks)

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