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Cytogenetics > 81 Cytogenetics > Flashcards

81 Cytogenetics Flashcards

1
Q

Cell whose chromosomes are an exact multiple of 23

A

Euploid

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2
Q

Euploid cells with more than the diploid number of 46

A

Polypoid

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3
Q

Polypoid conceptions are usually not viable, but the presence of ____ with a _____ can allow survival.

A

Presence of mosaicism with a karyotypically normal line

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4
Q

Abnormality defined as the presence of 2 or more cell lines in a single individual

A

Mosaicism

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5
Q

Cells with 3 haploid sets of chromosomes and are only viable in a mosaic form

A

Triploid

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6
Q

The phenotype of a triploid conception depends on the origin of the extra chromosome set. If the extra set is of paternal origin, it results in a _____. But triploid conceptions that have an extra se of maternal chromosomes results in ____.

A

Paternal - partial H mole with poor embryonic development.

Maternal - severe embryonic retardation with a small fibrotic placenta

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7
Q

Most common and clinically significant type of human chromosome abnormality

A

Aneuploidy

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8
Q

Aneuploidy occurs in at least ___% of all clinically recognized prenancies

A

3-4%

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9
Q

Abnormal cells that do not contain a multiple of haploid number of chromosomes

A

Aneuploid cells

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10
Q

Occur when only 1, instead of the normal 2, of a given chromosome is present in an otherwise diploid cell.

A

Monosomies

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11
Q

In humans, most autosomal monosomies appear to be lethal early in development, and survival is possible in ____ or by means of ____.

A

Mosaic forms or chromosome rescue

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12
Q

An exception to the rule of monosomies

A

Turner syndrome

Monosomy (45,X)

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13
Q

Most common cause of aneuploidy

A

Nondisjunction

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14
Q

Failure of chromosomes to disjoin normally during meiosis

A

Nondisjunction

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15
Q

Characterized by the presence of 3 chromosomes, instead of the normal 2, of any particular chromosome.

A

Trisomy

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16
Q

Most common form of aneuploidy

A

Trisomy

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17
Q

Technique that can be used for rapid diagnosis in the prenatal detection of common fetal aneuploidies

A

FISH

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18
Q

The most common type of trisomy in liveborn infants

A

Trisomy 21

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19
Q

The occurence of trisomy 21 and other trisomies increases with ____

A

Advanced maternal age ≥35 years old

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20
Q

Most common genetic etiology of moderate intellectual disability

A

Trisomy 21

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21
Q

The incidence of down syndrome in live births

A

1 in 733

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22
Q

Is sterility affected in down syndrome?

A

Yes, most males are sterile

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23
Q

Females with down syndrome have been able to reproduce, with a ____% chance of having trisomy 21 pregnancies

A

50%

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24
Q

Developmental delay in down syndrome

A

Universal

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25
Q

Area of development spared in down syndrome

A

Social

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26
Q

The life expectancy for children with Down syndrome

A

50-55 years old

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27
Q

Accounted for 60% of all cancers in people with down syndrome and 97% of all cancers in children with down syndrome

A

Leukemias

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28
Q

4 maternal tests used to screen for Down syndrome

A

BHCG, unconjugated estriol, inhibin, alpha fetoprotein

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29
Q

Time to screen for down syndrome

Congenital heart disease

A

Birth

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30
Q

Time to screen for down syndrome

Strabismus, cataracts, nystagmus

A

Birth or by 6 months

Check vision annually

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31
Q

Time to screen for down syndrome

Hearing impairment or loss

A

Birth or by 3 mos

Check hearing q6 mo up to 3 years if typmanic membrane not visualized; annually thereafter

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32
Q

Time to screen for down syndrome

Constipation

A

Birth

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33
Q

Time to screen for down syndrome

Celiac disease

A

At 2 years or with symptoms

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34
Q

Time to screen for down syndrome

Hematologic disease

A

Birth and in adolescence

35
Q

Time to screen for down syndrome

Hypothyroidism

A

Birth, repeat at 6-12 months old and annually

36
Q

Time to screen for down syndrome

Obstructive sleep apnea

A

1 yr and at each visit

37
Q

Time to screen for down syndrome

Atlantoaxial subluxation or instability

A

At each visit by history and PE
Radiographs at 3-5 or when planning to participate in contact sports
Radiographs when symtpomatic

38
Q

The origin of the supernumerary chromosome 21 is maternal/paternal in 97% as a result in errors in ___.

A

maternal errors in meiosis I

39
Q

The majority of translocations in down syndrome are fusions at the centromere between chromosomes ____

A

13, 14, 15, 21 and 22

40
Q

Most common form of chromosomal translocation in Down Syndrome

A

Robertsonian translocation

41
Q

Translocation (21;21) carriers have ___% recurrence risk for a chromosomally abnormal child

A

100%

42
Q

Other Robertsonian translocations such as t(14;21) have a __% recurrence risk when transmitted by females

A

5-7%

43
Q

Most commonly observed autosomal aneuploidy in spontaneous abortion

A

Trisomy 16

44
Q

Most common chromosome abnormalities seen in liveborn infants, children and adults

A

Sex chromosome abnormalities

45
Q

Characterized by complete or partial monosomy of the X chromosome and defined by a combination of phenotypic features

A

Turner syndrome

46
Q

Is maternal age a predisposing factor for children with 45,X?

A

No

47
Q

Turner syndrome occurs in approximately 1 in ____ female live births

A

5000

48
Q

It has been estimated that ____% of 45,X conceptions are miscarried

A

95-99%

49
Q

Common congenital defects associated with Turner syndrome

A

Structural renal anomalies (60%)

Congenital heart defects (40%)

50
Q

Most common heart defects associated with Turner syndrome

A

Bicuspid aortic valves
Coarctation of the aorta
Aortic stenosis
Mitral valve prolapse

51
Q

Intelligence of patients with Turner Syndrome

A

Normal

52
Q

Endocrinologic care for patients with Turner syndrome

A

Pubertal induction

Treatment with growth hormone and oxandrolone

53
Q

Patients with ____ can have Turner syndrome, although this form of mosaicism can also be associated with male pseudohermaphroditism, male or female genitalia in association with mixed gonadal dysgenesis or a normal male phenotype

A

45,X/46,XY mosaicism

54
Q

Phenotypic females with 45,X/46,XY mosaicism have a 15-30% risk of developing _____

A

Gonadoblastoma

55
Q

The APP has recommended the use of ____ to look for Y-chromosome mosaicism in all 45,X patients.

A

FISH analysis

56
Q

If Y chromosome maternal is identified in 45,X patients, _____ is recommended

A

Laparoscopic gonadectomy

57
Q

Noonan syndrome:

Autosomal dominant or recessive?

A

Autosomal dominant

58
Q

Most commonly involved gene in Noonan Syndrome

A

PTPN11 (50%)

59
Q

In contrast to Turner syndrome, Noonan syndrome affects ___ sexes, has a different pattern of congenital heart disease, typically involving _____.

A

Both

Right-sided lesions

60
Q

Most common cause of hypogonadism and infertility in males

A

Klinefelter syndrome

61
Q

Most common sex chromosome aneuploidy in humans

A

Klinefelter syndrome

62
Q

In klinefelter syndrome, the more greater the aneuploidy, the more severe the ___ and ____

A

Mental mpairment and dysmorphism

63
Q

Effect of klinefelter syndrome on puberty

A

Occurs at the normal age but testes are small, late secondary sex characteristics

64
Q

____% of patients with klinefelter syndrome develop Gynecomastia

A

50%

65
Q

Patients with ____ have a better prognosis for testicular function in klinefelter syndrome

A

46,XY/47,XXY

66
Q

Each additional X chromosome in klinefelter syndrome reduces the IQ by ____

A

10-15 points

67
Q

Main domains affected in development of Klinefelter syndrome

A

Language skills and social domains

68
Q

Regions of chromosomes that show a tendency for separation, breakage, or attenuation under particular growth conditions.

A

Fragile sites

69
Q

Fragile X syndrome is on which site of the chromosome?

A

Distal long arm of chromosome Xq27.3

70
Q

Jacobsen syndrome is associated with the deletion of the distal long arm of ____

A

Chromosome 11

71
Q

Main clinical manifestations of fragile X syndrome

A 
Intellectual disability
Autistic behavior
Macroorchidism
Hyperextensible finger joints
Characteristic facial features
72
Q

In fragile X syndrome, the larger the triplet expansion, the more significant the ____.

A

Intellectual disability

73
Q

Males with permutation triple repeat expansions have been found to have an adult, late onset progressive neurodegenerative disorder known as ____

A

fragile X-associated tremor/ataxia syndrome

74
Q

Two common errors of cell division that may occur during meiosis or mitosis

A

Nondisjunction

Anaphase lag

75
Q

Most commonly used banding and staining method in chromosome analysis

A

GTG banding

76
Q

Largest chromosome

A

1

77
Q

Smallest chromosome

A

22

78
Q

Used to identify the presence, absence, or rearrangement of specific DNA segments and is performed with gene-or region-specific DNA probes

A

Fluorescence in situ hybridization (FISH)

79
Q

Most common nondisjunction in aneuploidies

A

Maternal meiosis I

80
Q

Diagnosis

Cleft lip, flexed fingers with postaxial polydactyly, ocular hypotelorism, bulbous nose, microcephaly, low set-malformed ears, holoprosencephaly, microphthalmia, hypoplastic or absent ribs, visceral and genital anomalies

A

Patau Syndrome

81
Q

Diagnosis

LBW, closed fists with overlapping fingers, narrow hips, short sternum, rocker-bottom feet, microcephaly, prominent occiput, micrognathia, cardiac and renal malformations, intellectual disability

A

Edwards syndrome

82
Q

Diagnosis

Long face; high, prominent forehead; wide, upturned nose, thick, everted lower lip, microretrognathia, low-set ears; high-arched, sometimes cleft, palate, osteoarticular anomalies common, deep plantar and palmar creases

A

Trisomy 8,

mosaicism

83
Q

More common: Edwards or Patau?

A

Edwards

84
Q

More lethal: Edwards or Patau?

A

Edwards - 88% die in 1st yr

Patau - 80% die by 1 st yr

Cytogenetics (1 decks)

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