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Part II ISQ Club - Genetics

26 posts in this topic

Part II ISQs on two topics will be posted twice a week. You are encouraged to post a reply in the thread, stating whether you think an ISQ is true or false and why (eg. a short explanation, with reference to the textbook you used). Please only deal with one ISQ in each post and include the question as the first line of your post. All ISQs are taken from previous posts by Forum members.

In a few days this ISQ Club thread will be moved to the Question Bank board. If you submit an answer, your status will be changed to 'Question Bank member' and you will be able to see the Question Bank board. Please allow up to 48 hours for this change to happen.

1. Female carriers of Fragile-X have a below average IQ

2. The Fragile-X fragment occurs on the short arm of the X-chromosome

3. Klinefelter’s syndrome (XXY) is associated with moderate and severe learning difficulties in the majority of patients

4. Metachromatic leucodystrophy is an X-linked recessive condition

5. Restriction fragment length polymorphisms are inherited in a Mendelian fashion

6. Restriction fragment length polymorphisms are the only way to examine genetic linkage

7. Autism has a 90% MZ concordance rate

8. Linkage analysis can be used to study genetic disorders in families

9. A gene consists of coding information for intron, codon and mRNA

10. Most people with 47XYY do not have behavioural problems

11. Aggression is over-represented in 47XYY

12. Symptoms of Angelman’s syndrome include hyperphagia and cognitive impairment

13. Uniparental disomy is more a cause of Angelmann’s syndrome than Prader Willi syndrome

14. An imperforate anus at birth suggests Down’s syndrome

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1 true

2false Xq long arm

metachromatic leucodystrophy autosomal recessive

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Klinefelters syndrome question is false, they uss have mild ld

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Q4. False.  Metachromatic leucodystrophy is  an autosomal recessive metabolic disorder.

Q10. True

Q11. False? see below

XYY causes slight increased height, slightly decreased IQ.  Increased incidence in Prisons suggests increased behaviour probs and agression, but no causal link proven.

But Hey - lower IQ= more behavioural problems. So, Q11 is ambiguous. For a change..

Puri and Tyrer. Sciences Basic to Psychiatry.

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12. false hyperphagia and cognitive impairment symptoms of prader willi syndrome (the Paternal deletion of same genes) if maternal deletion get angelmans syndrome with midline handflapping and MR. an example of uniparetnal disomy aka imprinting

UPD causes equal amounts of PW and Angelman

13. true imperforate anus suggestive of downs, as is dudodenal atresia, prolonged meconium ileus, prolonged neonatal jaundince, floppy baby

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12. false hyperphagia and cognitive impairment symptoms of prader willi syndrome (the Paternal deletion of same genes) if maternal deletion get angelmans syndrome with midline handflapping and MR. an example of uniparetnal disomy aka imprinting

UPD causes equal amounts of PW and Angelman

13. true imperforate anus suggestive of downs, as is dudodenal atresia, prolonged meconium ileus, prolonged neonatal jaundince, floppy baby

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7 Autism has a 90% MZ concordance rate.

False

2 largest twin studies show 36% MZ vs 0% DZ in one study and 96% MZ vs 27% DZ in second study.Second study, however, zygosity was confirmed in only about half the sample.

Synopsis of Psychiatry, Kaplan and Saddock

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1 true ,30 to 50% of the female carriers show cognitive deficit[oxford page 1954]

2false lonng arm Xq 27.3 [ox 1953]

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3 false mild mental retardation in 47 XXY[may have an IQ in the normal range]severe mental retardation in rarer genoypic variations [puri pg 184]

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 8) Linkage analysis can be used to study genetic disorders in families

True - ref companion page 227

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13. Uniparental disomy is more a cause of Angelmann’s syndrome than Prader Willi syndrome

FALSE

Occurs in both, but more in Prader-Willi (25%) cf Angelman (2%)

(Pg 224, Comp to Psych St, 6th Ed, Johnstone et al)

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11. Aggression is over-represented in 47XYY

FALSE

(Pg 205, Exam Notes in Psych, Basic Sc, Malhi & Mitchell)

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10. Most people with 47XYY do not have behavioural problems

FALSE

(Pg 612, Comp to Psych St, 6th Ed, Johnstone et al)

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6. Restriction fragment length polymorphisms are the only way to examine genetic linkage

FALSE

(Pg 95, Oxford Txt of Psych, 3rd Ed, Gelder et al)

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7. Autism has a 90% MZ concordance rate

TRUE

“…the huge disparity in concordance rates for autism between MZ (n = 25) and DZ (n = 20) pairs (60% vs. 5%) confirmed the earlier findings on the strength of the genetic influence. Quantitative analyses indicated a heritability in excess of 90%.

http://www.findarticles.com/cf_dls/m0902/1_28/61969746/p2/article.jhtml?term=

“Current heritability estimates for autism are above 90%, which makes autism a strongly genetic disorder.”

http://www.cpa-apc.org/Publications/Archives/CJP/2003/september/guesteditorial.asp

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9. A gene consists of coding information for intron, codon and mRNA

FALSE

(Pg 220, Comp to Psych St, 6th Ed, Johnstone et al)

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14. An imperforate anus at birth suggests Down’s syndrome

FALSE

Suggest VACTERL syndrome

http://www.pedisurg.com/PtEduc/Imperforate_Anus.htm

What is imperforate anus?

Imperforate anus is the absence of a normal anal opening. The diagnosis is usually made shortly after birth by a routine physical examination. Imperforate anus occurs in about 1 in 5000 births and its cause is unknown.

Children who have imperforate anus may also have other congenital anomalies. The acronym VACTERL describes the associated problems that infants with imperforate anus may have: Vertebral defects, Anal atresia, Cardiac anomalies, Tracheoesophageal fistula, Esophageal atresia, Renal anomalies, and Limb anomalies. The incidence of kidney and bladder problems increases with the severity of the imperforate anus, ranging from 5 to 20 percent with low lesions up to 60 to 90 percent with high lesions. While some of these anomalies may be noted on physical examination, others require further diagnostic tests. Renal ultrasound is done shortly after birth on all infants to evaluate the kidneys. Chest X-ray, EKG, and cardiac ultrasound may be ordered to evaluate the heart. Other X-rays may be done to evaluate the trachea and esophagus and the spine.

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1. Female carriers of Fragile-X have a below average IQ

1]TRUE

It is the 2nd most common single cause of mental retardation. It can range from mild to severe. The intellectual functions seem to decline in the pubertal period. Females are less impaired than  males  but can be mildly retarded.

Kaplan & Sadock- Synopsis of Psychiatry 9th Edition

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7. Autism has a 90% MZ concordance rate

TRUE

“…the huge disparity in concordance rates for autism between MZ (n = 25) and DZ (n = 20) pairs (60% vs. 5%) confirmed the earlier findings on the strength of the genetic influence. Quantitative analyses indicated a heritability in excess of 90%.

http://www.findarticles.com/cf_dls/m0902/1_28/61969746/p2/article.jhtml?term=

“Current heritability estimates for autism are above 90%, which makes autism a strongly genetic disorder.”

http://www.cpa-apc.org/Publications/Archives/CJP/2003/september/guesteditorial.asp

The above quote in itself indicates that 7. 90% MZ concordance - False!

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5. RFLP patterns are inherited and segregate in Mendelian fashion thus, allowing their use in genotyping such as in cases of paternity dispute or in criminal investigations. -true

6. Restriction fragment length polymorphisms are the only way to examine genetic linkage - false (this is more a statistical procedure ...)

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Q: Female carriers of Fragile X have subnormal IQ

A: True, Females (1:2000)are usually carriers but can express phenotypical features and have mental retardation

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Q:2 = Fragile X on Short arm of chromosome X

A:2 = False, Long arm

Ref. Gin S. Malhi

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autism has a 90% monozygotic concordance rate..T

after getting confused i seatched ovid data base for estimates of concordance for autism.......

The UCLA Registry for Genetic Studies in Autism was established in 1980 to test the hypothesis that genetic factors may be etiologically significant in subsets of patients. To date 61 pairs of twins have enrolled and 40 meet research diagnostic criteria for autism. The authors found a concordance for autism in these 40 pairs of 95.7% in the monozygotic twins (22 of 23) and 23.5% in the dizygotic twins (four of 17).

Am J Psychiatry. 142(1):74-7, 1985 Jan.

Autism is a neurodevelopmental disorder of genetic origins, with a heritability of about 90%.

American Journal of PharmacoGenomics. 5(2):71-92, 2005

Genetic predisposition to autism is evident from family and twin studies, and heritability in idiopathic autism is estimated at over 90%.

Annals of Medicine. 35(4):274-281, 2003

In the combined sample 60% of monozygotic (MZ) pairs were concordant for autism versus no dizygotic (DZ) pairs

Psychological Medicine. 25(1):63-78, January 1995.

Twin studies reported 60% concordance for classic autism in monozygotic (MZ) twins versus 0 in dizygotic (DZ) twins

The recurrence rate in siblings of affected children is approximately 2% to 8%

Pediatrics. 113(5):e472-86, 2004 May.

A higher recurrence risk in families with autistic subjects (45 times greater than the prevalence in the general population) and higher concordance for autism among monozygotic (60-90%) than dizygotic (0-10%) twins argue for a genetic predisposition to idiopathic autism.

M S-Medecine Sciences. 19(11):1081-90, 2003 Nov.

The concordance for autism by pair was 91% in the monoygotic and 0% in the dizygotic pairs.

J Child Psychol Psychiatry. 30(3):405-16, 1989 May.

Autism is familial, as reflected in an empiric sibling recurrence risk of 3% and pooled monozygotic and dizygotic concordance rates of 64% and 9%, respectively, which are much greater than the population prevalence of 0.02% to 0.05%.

Archives of General Psychiatry. 45(10):953-61, 1988 Oct.

The authors found a concordance for autism in these 40 pairs of 95.7% in the monozygotic twins (22 of 23) and 23.5% in the dizygotic twins (four of 17).

Am J Psychiatry. 142(1):74-7, 1985 Jan.

so i'd say 90% is about right

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