Sex Determination-Nuclear Sexing

Sex Determination-Nuclear Sexing

Q. 1

Barr body is seen in :

 A

Turners syndrome

 B

Klinefelters syndromeTesticular feminisation

 C

Tesiicular leminisation syndrome

 D

46 XY

Q. 1

Barr body is seen in :

 A

Turners syndrome

 B

Klinefelters syndromeTesticular feminisation

 C

Tesiicular leminisation syndrome

 D

46 XY

Ans. B

Explanation:

Klinefelters syndrome


Q. 2 Sex can be established by examining hair root cells for the presence of:
 A Davidson body
 B Barr body
 C Golgi body
 D Medullary index
Q. 2 Sex can be established by examining hair root cells for the presence of:
 A Davidson body
 B Barr body
 C Golgi body
 D Medullary index
Ans. B

Explanation:

Barr body


Q. 3

Chromosomal analysis of all of the following genotype shows Barr bodies, EXCEPT:

 A

XO

 B

XXY

 C

XX

 D

XXX

Q. 3

Chromosomal analysis of all of the following genotype shows Barr bodies, EXCEPT:

 A

XO

 B

XXY

 C

XX

 D

XXX

Ans. A

Explanation:

Routine microscopy of mammalian cell nuclei reveals a small, dense mass of heterochromatin present in females but not males. This “sex chromatin” (or Barr body or X-chromatin) is one of the two X chromosomes present in females.

As a general rule, only 1 X chromosome functions in a cell at a given time. All other X chromosomes present in a cell may be seen as X-chromatin bodies in a resting nucleus.

Thus, if one knows the number of X chromosomes, one can anticipate that the number of Barr bodies will be 1 less. If one counts the number of Barr bodies, the number of X chromosomes can be determined by adding 1. Hence Barr bodies are not seen in genotype XO.

The male cell has one X chromosome and one Y chromosome, therefore no sex chromatin is visible in males.

Ref: Manipalviratn S., Trivax B., Huang A. (2013). Chapter 3. Genetic Disorders & Sex Chromosome Abnormalities. In A.H. DeCherney, L. Nathan, N. Laufer, A.S. Roman (Eds), CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.

Quiz In Between


Q. 4

Barr body is found in the following phase of the cell cycle:

 A

Interphase

 B

Metaphase

 C

GI phase

 D

Telophase

Q. 4

Barr body is found in the following phase of the cell cycle:

 A

Interphase

 B

Metaphase

 C

GI phase

 D

Telophase

Ans. A

Explanation:

A i.e. Interphase

The inactive X can be seen in the interphase nucleus as a darkly staining small mass in contact with the nuclear membrane known as the Barr body or X chromatin. Barr body is the inactivated X chromosome. In non dividing interphase cells it remains tightly coiled and can be seen as a dark staining body within the nucleus.


Q. 5

Barr body is absent in female having ‑

 A

46 XX genome

 B

45 X0 genome

 C

47 XXX

 D

All of above

Q. 5

Barr body is absent in female having ‑

 A

46 XX genome

 B

45 X0 genome

 C

47 XXX

 D

All of above

Ans. B

Explanation:

Ans. is ‘b’ i.e., 45 X0 genome

Barr body (Sex – chromatin)

o It is a densely staining inactivated condensed ‘X’ chromosome that is present in each somatic cells of female.

o It is found in the nucleus.

o It is used as a test of genetic femaleness it is possible to determine the genetic sex of an individual according as to whether there is a chromatin mass present on the inner surface of the nuclear membrane of cells with resting or intermitent nuclei. Remember following fact and the question will seem very easy.

  • Chromatid body (Barr body or sex chromatin) is derived from one of the two X-chromosomes which becomes inactivated.
  • The numer of Barr bodies is thus one less than the number of X-chromosomes.

Note –

o  Barr body is found in female But –

o  Kleinefelter syndrome is male with Barr body.

o  Turner syndrome is female without Barr body.


Q. 6

Males who are sexually under developled with rudimentary testes and prostate glands, sparse pubic and facial hair, long arms and legs and large hands & feet are likely to have the chromosome complement of :

 A

45, XYY

 B

46, XY

 C

46, XXY

 D

46, X

Q. 6

Males who are sexually under developled with rudimentary testes and prostate glands, sparse pubic and facial hair, long arms and legs and large hands & feet are likely to have the chromosome complement of :

 A

45, XYY

 B

46, XY

 C

46, XXY

 D

46, X

Ans. C

Explanation:

Answer is C (46, XXY) :

The patient in question depicts a hypogonadic male that occurs when there are two or more X chromosomes, (47XX Y) and one Y chromosome, and represents the clinical picture of klinefelter’s syndrome.

None of the options appear technically correct as an extra X chromosome in the male should increase the total number of chromosomes to 47 and hence 47 XXY should be the most appropriate answer.

Within the available options however an extra X-chromosome is the most essential aspect and hence the best answer here is 46 XXY.

Klinefelter’s Syndrome: 47 XXV or 46 X,Y / 47 XXY Mosaicism

  • Small firm testes: Hyalinization of seminiferous tubules and azoospermia
  • Gynaecomastia
  • Lack of secondary male characters such as deep voice, beard, male distribution of pubic hair 
  • Distinct body habitus: Elongated body: Abnormally long leg
  • The mean IQ is some what lower than normal but mental retardation is uncommon 
  • Hypogonadism and in fertility
  • Klinefelter’s syndrome is produced by non disjunction during meiotic divisions

Quiz In Between


Q. 7

Sex chromosome pattern in Klinefelter’s syndrome is:

March 2004

 A

XXY

 B

XO

 C

XX

 D

XY

Q. 7

Sex chromosome pattern in Klinefelter’s syndrome is:

March 2004

 A

XXY

 B

XO

 C

XX

 D

XY

Ans. A

Explanation:

Ans. A i.e. XXY


Q. 8

Barr body was first detected in:

DNB 08

 A

Buccal mucosa

 B

Brain

 C

Liver

 D

Skin

Q. 8

Barr body was first detected in:

DNB 08

 A

Buccal mucosa

 B

Brain

 C

Liver

 D

Skin

Ans. B

Explanation:

Ans. Brain

Quiz In Between


Q. 9

Sex determining region is located on ‑

 A

Long arm of Y chromosome

 B

Short arm of Y chromosome

 C

Long arm of X chromosome

 D

Short arm of X chromosome

Q. 9

Sex determining region is located on ‑

 A

Long arm of Y chromosome

 B

Short arm of Y chromosome

 C

Long arm of X chromosome

 D

Short arm of X chromosome

Ans. B

Explanation:

 

Product of SRY gene is sex-determining region Y protein.

This protein is involved in male sexual development.


Q. 10

Barr body is absent in ‑

 A

Kleinfelter

 B

Turner

 C

Super female

 D

None of the above

Q. 10

Barr body is absent in ‑

 A

Kleinfelter

 B

Turner

 C

Super female

 D

None of the above

Ans. B

Explanation:

Ans. is ‘b’ i.e., Turner

Barr body (Sex – chromatin)

  • It is a densely staining inactivated condensed ‘X’ chromosome that is present in each somatic cells of female. o It is found in the nucleus.
  • It is used as a test of genetic femaleness -4 it is possible to determine the genetic sex of an individual according as to whether there is a chromatin mass present on the inner surface of the nuclear membrane of cells with resting or intermitent nuclei. Remember following fact and the question will seem very easy.
  • Chromatid body (Barr body or sex chromatin) is derived from one of the two X-chromosomes which becomes inactivated.
  • The numer of Barr bodies is thus one less than the number of X-chromosomes.

Quiz In Between



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