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Gametogenesis > Sex chromosome aberrations > Flashcards

Sex chromosome aberrations Flashcards

1
Q

Incidence rate of Turner’s syndrome?

A

1 in 2000 to 1 in 5000 female births

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2
Q

Karyotype notation of Turner syndrome?

A

45, X

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3
Q

T/F. Over 99% of fetuses affected with Turner syndrome spontaneously abort.

A

True.

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4
Q

This sex chromosome aberration can be suggested in the newborn by redundant neck skin & peripheral lymphoedema.

A

Turner syndrome

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5
Q

Diagnosis of Turner syndrome is frequently made later, during the investigation of _____.

A

short stature or primary amenorrhoea

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6
Q

In newborns with Turner syndrome, no adolescent growth spurt occurs, and the mean adult height, if untreated, is ____ with a correlation to ____.

A

145 cm; mid - parental height

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7
Q

T/F. In newborns with Turner syndrome, chest tends to be broad, with the impression of narrowly spaced nipples, the hair line is high and the neck may be webbed.

A

False. Broad chest, widely spaced nipples, hairline is low, webbed neck

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8
Q

T/F. In newborns with Turner syndrome, elbow carrying angle may be decreased and the fourth metacarpals long.

A

False. Elbow carrying angle is increased and fourth metacarpals are short.

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9
Q

In newborns with Turner syndrome, ____ of the nails and ___ are common.

A

hypoplasia; multiple pigmented naevi

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10
Q

___ occurs at some stage in 40% of patient with Turner syndrome.

A

Peripheral lymphoedema

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11
Q

T/F. Occasionally, ovarian degeneration is incomplete in patients with Turner syndrome, menses may occur (10 – 15%) and, rarely, a pregnancy may be possible.

A

True.

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12
Q

In newborns with Turner syndrome, ova begin to degenerate and disappear after the 15 week of gestation, so that at birth the ovaries are represented by ____, and this results in failure of _____.

A

streaks; secondary sexual development.

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13
Q

What are the common cardiac abnormalities present in 50% of patients with Turner syndrome.

A

bicuspid aortic valve, coarctation of the aorta, atrial septal defect, and aortic stenosis

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14
Q

T/F. An increased risk of unexplained systemic hypertension (27%), renal malformations, Hashimoto thyroiditis, Crohn disease and gastrointestinal bleeding is associated with Turner syndrome.

A

True.

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15
Q

T/F. Intelligence and lifespan of patients with Turner syndrome may also be affected.

A

False. Both are normal

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16
Q

In patients with Turner syndrome, ____ will allow the development of secondary sexual characteristics, and treatment with ____ in childhood has been shown to increase the final height by at least 5 cm.

A

sex hormone replacement; growth hormone

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17
Q

Normal childbirth has been achieved by ___ using donor oocyte in patients with Turner syndrome.

A

in vitro fertilization

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18
Q

In 80% of patients w/ monosomy X, only the maternal X chromosome is present, and thus the error occurred in ____.

A

spermatogenesis or post-fertilization

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19
Q

T/F. There is lack of maternal age effect in the incidence of monosomy X.

A

True. 80 percent of the time, monosomy X occurs due to nondisjunction in the spermatogenesis or due to anaphase lag post fertilization.

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20
Q

T/F. In monosomy X, the sex chromatin body is absent from nuclei.

A

True.

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21
Q

T/F. Overall, 50% of patients have 45,X, 17% have an isochromosome of the long arm of X, 24% are mosaics, 7% have a ring X and 2% have a short arm deletion of one X.

A

True.

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22
Q

T/F. In general, deletion of the long arm of the X is associated with the Turner phenotype, while short - arm deletions alone produce streak ovaries without the associated dysmorphic features.

A

False. Long arm deletion - streak ovaries without dysmorphic features; short arm deletion - complete turner phenotype

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23
Q

In 4% of patients affected with Turner syndrome, ____ with a second cell line containing a Y chromosome is found.

A

mosaicism

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24
Q

In patient with mosaic monosomy of X, , there is a risk of up to 20% that the streak gonad will develop a ____, which can progress to a ____, and gonadal removal is generally recommended.

A

gonadoblastoma; dysgerminoma

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25
Q

T/F. Genotype/phenotype correlation is defined in mosaic monosomy of X.

A

False. Poor genotype-phenotype correlation , possibly as a result of varying extents of mosaicism for a normal cell line (45,X/46,XX) in different tissues.

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26
Q

Short stature, which is present in around 95% of cases of Turner syndrome, is caused at least in part by haploinsufficiency of the ____ gene located on ____, which encodes a transcription factor that is especially important during limb development.

A

SHOX; Xp

27
Q

T/F. The recurrence risk of Turner syndrome does not appear to be increased above the general population risk.

A

True.

28
Q

What is the incidence of 47, XYY?

A

1 in 1000 male births

29
Q

Patients with 47, XYY tends to have an IQ ____ points less than their normal siblings, and behaviour problems with easy ____ and ____ may occur.

A

10-15; frustration; aggression

29
Q

47, XYY accounts for ___ adult males who are in institutions on account of significant learning difficulties or criminal behaviour.

A

20 per 1000

30
Q

T/F. There is no apparent parental age effect in incidence of 47, XYY.

A

True.

31
Q

T/F. Patients with Jacob’s syndrome is often symptomatic and most 47,XYY men have learning difficulties or criminal behaviour.

A

False. 47, XYY often asymptomatic; usually no learning difficulty or criminal behaviour.

32
Q

T/F. Patients with 47, XYY tend to be short, but have normal body proportions and no other clinical signs.

A

False. They tend to be tall.

33
Q

Causes of 47, XYY

A

production of YY sperm by nondisjunction at the second paternal meiotic division

mitotic non disjunction of the Y chromosome during post fertilization

34
Q

What disease has a karyotype notation of 47, XYY

A

Jacob’s syndrome

35
Q

For a person w/ 47, XYY, the expected ratio of off spring would be:

A

2 XXY: 1 XYY: 2 XY: 1 XX

36
Q

T/F. The recurrence risk is probably not increased for the parents of an affected child with 47, XYY.

A

True.

37
Q

T/F. In practice, fertility appears impaired in most cases of Jacob’s syndrome, and affected patients are observed to have XX and XY off spring only.

A

False. While only XX and XY offspring are observed, fertility is not impaired in most cases.

38
Q

47 XXY represents what disease?

A

Klinefelter syndrome

39
Q

What is the incidence of Klinefelter syndrome?

A

1 in 1000 males

40
Q

T/F. Maternal age effect is observed in incidence of Klinefelter.

A

True. Increased risk of occurring in offspring with maternal age

41
Q

T/F. Frequency of 47, XXY is increased amongst azoospermic infertile males (1 in 10) and in males with significant learning difficulties (1 in 100).

A

True.

42
Q

The diagnosis of Klinefelter is generally made during adult life at the investigation of infertility, as this is the single commonest cause of ____ and ____ in men.

A

hypogonadism; infertility

43
Q

T/F. In patients with Klinefelter syndrome, the testes are small (less than 2 cm long in the adult) but are able to produce adult levels of testosterone.

A

False. Small testes and low production of testosterone

44
Q

The low production of testosterone in male with Klinefelter syndrome leads to poorly developed ____ and ____.

A

secondary sexual characteristics; gynaecomastia

45
Q

____ from early adolescence will improve secondary sexual characteristics in 47 XXY patients and help to prevent osteoporosis, but infertility is the rule, except in ____ patients.

A

Testosterone replacement therapy; mosaic

45
Q

T/F. In male with Klinefelter syndrome, the limbs are elongated from early childhood and the upper to lower segment ratio is abnormally low with a mean adult height close to the 75th percentile.

A

True.

46
Q

T/F. Scoliosis, emphysema, diabetes mellitus (8%) and osteoporosis may occur in males with Klinefelter, and the frequency of carcinoma of the breast is higher to that for normal females.

A

False. Similar risk of developing breast cancer

47
Q

In some males with Klinefelter, fertility has been achieved using ____ and ____.

A

testicular sperm aspiration;intracytoplasmic sperm injection (ICSI)

48
Q

In males with Klinefelter syndrome, there is a ___ - point reduction in verbal skills, but performance scores are usually normal and severe learning difficulties are uncommon. Behavioural problems are common in childhood.

A

10 – 20

49
Q

T/F. In males with Klinefelter syndrome, extra X chromosome is of maternal origin in 56% and paternal in 44% of patients.

A

True.

50
Q

Genetic causes of Klinefelter syndrome

A

Maternal or paternal nondisjunction at the first or second meiotic devision

Mitotic error after fertilization (rare)

51
Q

In the male, Klinefelter syndrome arises when the first meiotic division produces an ____ and this is favoured if the normal single XY cross - over is lost or fails to occur during male meiosis.

A

XY sperm

52
Q

T/F. The recurrence risk of Klinefelter syndrome does not appear to be increased above the general population risk.

A

True.

53
Q

Patients with ____ and ____ have severe learning difficulties and _____ is a common skeletal defect.

A

48,XXXY; 49,XXXXY; proximal radioulnar synostosis

54
Q

47, XXX represents what syndrome?

A

Triple X syndrome

55
Q

What is the incidence frequency of tripple X syndrome?

A

1 in 1000 females

55
Q

T/F. Triple X syndrome is associated with maternal age effect.

A

True.

56
Q

T/F. Individuals with triple X syndrome appear clinically normal, but 15 – 25% have mild learning difficulties.

A

True.

56
Q

Genetic causes of triple X syndrome

A

first or second maternal meiotic non disjunction
second paternal meiotic non disjunction
post-zygotic mitotic error

57
Q

T/F. The recurrence risk for triple X syndrome does not appear to be increased above the general population incidence.

A

True.

58
Q

T/F. About three - quarters of females affected with triple X syndrome are non fertile.

A

False. Fertile

59
Q

___ of the offspring of an female affected with triple X syndrome would be expected to be affected, but in practice they are usually normal.

A

One – half

60
Q

T/F. The more the X chromosome, the more severe the learning difficulty is.

A

True.

Gametogenesis (9 decks)

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