Sex chromosome aberrations

Question 1

Incidence rate of Turner’s syndrome?

Answer 1

1 in 2000 to 1 in 5000 female births

Question 2

Karyotype notation of Turner syndrome?

Answer 2

45, X

Question 3

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

Answer 3

True.

Question 4

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

Answer 4

Turner syndrome

Question 5

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

Answer 5

short stature or primary amenorrhoea

Question 6

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

Answer 6

145 cm; mid - parental height

Question 7

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.

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

hypoplasia; multiple pigmented naevi

Question 10

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

Answer 10

Peripheral lymphoedema

Question 11

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

Answer 11

True.

Question 12

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 _____.

Answer 12

streaks; secondary sexual development.

Question 13

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

Answer 13

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

Question 14

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

Answer 14

True.

Question 15

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

Answer 15

False. Both are normal

Question 16

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.

Answer 16

sex hormone replacement; growth hormone

Question 17

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

Answer 17

in vitro fertilization

Question 18

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

Answer 18

spermatogenesis or post-fertilization

Question 19

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

Answer 19

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

Question 20

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

Answer 20

True.

Question 21

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.

Answer 21

True.

Question 22

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.

Answer 22

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

Question 23

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

Answer 23

mosaicism

Question 24

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.

Answer 24

gonadoblastoma; dysgerminoma

Question 25

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

Answer 25

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.

Question 26

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.

Answer 26

SHOX; Xp

Question 27

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

Answer 27

True.

Question 28

What is the incidence of 47, XYY?

Answer 28

1 in 1000 male births

Question 29

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

Answer 29

10-15; frustration; aggression

Question 29

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

Answer 29

20 per 1000

Question 30

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

Answer 30

True.

Question 31

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

Answer 31

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

Question 32

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

Answer 32

False. They tend to be tall.

Question 33

Causes of 47, XYY

Answer 33

production of YY sperm by nondisjunction at the second paternal meiotic division mitotic non disjunction of the Y chromosome during post fertilization

Question 34

What disease has a karyotype notation of 47, XYY

Answer 34

Jacob's syndrome

Question 35

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

Answer 35

2 XXY: 1 XYY: 2 XY: 1 XX

Question 36

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

Answer 36

True.

Question 37

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.

Answer 37

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

Question 38

47 XXY represents what disease?

Answer 38

Klinefelter syndrome

Question 39

What is the incidence of Klinefelter syndrome?

Answer 39

1 in 1000 males

Question 40

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

Answer 40

True. Increased risk of occurring in offspring with maternal age

Question 41

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).

Answer 41

True.

Question 42

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.

Answer 42

hypogonadism; infertility

Question 43

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.

Answer 43

False. Small testes and low production of testosterone

Question 44

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

Answer 44

secondary sexual characteristics; gynaecomastia

Question 45

____ 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.

Answer 45

Testosterone replacement therapy; mosaic

Question 45

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.

Answer 45

True.

Question 46

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.

Answer 46

False. Similar risk of developing breast cancer

Question 47

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

Answer 47

testicular sperm aspiration;intracytoplasmic sperm injection (ICSI)

Question 48

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.

Answer 48

10 – 20

Question 49

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

Answer 49

True.

Question 50

Genetic causes of Klinefelter syndrome

Answer 50

Maternal or paternal nondisjunction at the first or second meiotic devision Mitotic error after fertilization (rare)

Question 51

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.

Answer 51

XY sperm

Question 52

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

Answer 52

True.

Question 53

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

Answer 53

48,XXXY; 49,XXXXY; proximal radioulnar synostosis

Question 54

47, XXX represents what syndrome?

Answer 54

Triple X syndrome

Question 55

What is the incidence frequency of tripple X syndrome?

Answer 55

1 in 1000 females

Question 55

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

Answer 55

True.

Question 56

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

Answer 56

True.

Question 56

Genetic causes of triple X syndrome

Answer 56

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

Question 57

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

Answer 57

True.

Question 58

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

Answer 58

False. Fertile

Question 59

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

Answer 59

One – half

Question 60

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

Answer 60

True.