Sex Determination-Nuclear Sexing
Most Certain Evidences
- Presence of testis in males & ovaries in females.
- Shown by ejaculation & menstruation respectively after puberty in males & females.
Highly probable evidence
- Females: Presence of breast, vagina, appropriate muscular development, absence of moustache, beard, chest hair.
- Males: Absence of breast tissue, appropriate muscular development,
- Presence of penis, moustache, beard, chest hair
Presumptive evidence
- Face
- Dress
- Costume
- Hair
- Voice
Nuclear Sexing
- The sex can be determined by studying the presence of:
- Barr bodies
- Davidson’s bodies and
- ‘Y’ chromosomes.
Barr bodies (Sex Chromatin)
- It is plano-convex nuclear condensation seen at the inner surface of the nuclear membrane.
- First detected in brain.
- In females more than 40% of nuclei of buccal mucosa contain chromatin body (chromatin positive),
- In males only less than 10% of nuclei contain chromatin body (chromatin negative).
- The ideal tissues to study Barr bodies are buccal mucosa, skin, smooth muscle and cartilage.
- Medico-Legal Importance: To differentiate between males & females
Davidson Bodies
- In females,upto6% of polymorphic W.B.C’s (i.e. neutrophils and eosinophils) show a thin stalked drumstick like projection at the periphery of the nucleus.
- This is absent in males
Y- Chromosomes
- The ‘Y’ Chromosomes present in males are fluroscent for the dye Quinacrine dihydrochloride.
- Blood stains, cartilage, bone marrow, teeth pulp and hair root pulp can be used as specimens.
Intersex States
- These are the conditions wherein both male and female characters coexist in varying degrees in the same individual.
- Gonadal agenesis – gonads (either ovaries or testes) fail to develop. The nuclear sex is chromatin negative.
- Gonadal dysgenesis – External genital organs are present, but the testes or ovaries fail to develop at puberty.
Gonadal dysgenesis
a. Klinefelter’s syndrome
- Anatomical structure in male, but the nuclear sexing is female (chromatin positive).
- Barr bodies present
- The chromosomal pattern is 47XXY
- Usually undiagnosed till puberty.
- Testes are small & firm in consistency, aspermia, No semen, Hyalinised testis (histologically).
- Gynaecomastia is usual finding.
- Sexual Euinacioidism (long arm& legs, scanty public hair growth. may not have hair growth over face)
- Person is usually tall with long slender arm’s & legs, scanty or absent facial hair, axillary hair and pubic hair, thin voice (Sexual Euinacioidism).
b.Turner’s syndrome
- Anatomical structure is female nuclear sexing is male (chromatin negative).
- Barr bodies absent
- The chromosomal pattern is 45 XO
- The person is usually of short stature.
- There is lack of development of secondary sexual characteristics associated with primary amenorrhoea, grossly undeveloped breast with widely spaced nipples, scanty public & axillary hair, infantile tubes and streak ovaries (no ovarian follicle, contains fibrous tissue).
- Congenital anomalies like Web neck, cubitus valgus, coarctation of aorta, osteoporosis, renal abnormalities, red-green colour blindness.
True hermaphroditism
- A rare condition,wherein external genitalia may be of both sexes, but internally there is presence of both testes & ovaries and ovotestes
Pseudohermaphroditism
- External characteristics of one sex, with gonads of opposite sex
a.Male pseudohermaphroditism:
- Nuclear sex XY, sex organs & sexual characteristic of female form
b.Female pseudohermaphroditism:
- Nuclear sex XX, sex organs & sexual characteristic of male form
Medico-Legal Importance of sex
- Marriage, divorce, Nullity of marriage, inheritance, rape, maternity, paternity, employment, contesting for election & other civil rights.
Exam Important
Nuclear Sexing
- The sex can be determined by studying the presence of:
- Barr bodies
- Davidson’s bodies and
- ‘Y’ chromosomes.
Barr bodies (Sex Chromatin)
- First detected in brain.
- In females more than 40% of nuclei of buccal mucosa contain chromatin body (chromatin positive),
- In males only less than 10% of nuclei contain chromatin body (chromatin negative).
Davidson Bodies
- This is absent in males
Y- Chromosomes
- The ‘Y’ Chromosomes present in males are fluroscent for the dye Quinacrine dihydrochloride.
Intersex States
Gonadal dysgenesis
a. Klinefelter’s syndrome
- Anatomical structure in male, but the nuclear sexing is female (chromatin positive).
- Barr bodies present
- The chromosomal pattern is 47XXY
- Testes are small & firm in consistency, aspermia, No semen, Hyalinised testis (histologically).
b.Turner’s syndrome
- Anatomical structure is female nuclear sexing is male (chromatin negative).
- Barr bodies absent
- The chromosomal pattern is 45 XO
True hermaphroditism
- A rare condition,wherein external genitalia may be of both sexes, but internally there is presence of both testes & ovaries and ovotestes
Pseudohermaphroditism
- External characteristics of one sex, with gonads of opposite sex
a.Male pseudohermaphroditism:
- Nuclear sex XY, sex organs & sexual characteristic of female form
b.Female pseudohermaphroditism:
- Nuclear sex XX, sex organs & sexual characteristic of male form
Medico-Legal Importance of sex
- Marriage, divorce, Nullity of marriage, inheritance, rape, maternity, paternity, employment, contesting for election & other civil rights.
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