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FREE MARTIN

21st November, 2023

FREE MARTIN

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Context

  • In agricultural settings, because freemartins can’t reproduce, farmers often identify them through physical and/or behavioural traits.

Freemartin

  • A freemartin is an infertile female cattle with masculinized behavior and non-functioning ovaries.
  • Phenotypically, the animal appears female, but various aspects of female reproductive development are altered due to acquisition of anti-Müllerian hormone from the male twin.
  • Genetically, the animal is chimeric: karyotypy of a sample of cells shows XX/XY chromosomes.
  • The animal originates as a female (XX), but acquires the male (XY) component in utero by exchange of some cellular material from a male twin, via vascular connections between placentas: an example of microchimerism.
  • The chimerism is mainly present in the hematopoietic stem cells.

Mechanism

  • In most cattle twins, the blood vessels in the chorions become interconnected, creating a shared circulation for both twins.
  • If both foetuses are the same sex this is of no significance, but if they are different, male hormones pass from the male twin to the female twin.
  • The male hormones (testosterone and anti-Müllerian hormone) then masculinize the female twin, and the result is a freemartin.
  • The degree of masculinization is greater if the fusion occurs earlier in the pregnancy – in about ten percent of cases no fusion takes place and the female remains fertile.
  • The male twin is largely unaffected by the fusion, although the size of the testicles may be slightly reduced.
  • Testicle size is associated with fertility, so there may be some reduction in bull fertility.
  • Freemartins behave and grow in a similar way to castrated male cattle (steers).

PRACTICE QUESTION

Q. Recently, Freemartin was in the news. What is it?

1.    An animal that has both male and female sexual organs.

2.    A reproductive strategy that involves development of a female gamete  without fertilization.

3.    Infertile female cattle with masculinized behavior.

4.    Multiplication of genetically identical copies of a cultivar by asexual reproduction.

Choose the correct code.

  1. A
  2. B
  3. C
  4. D

Answer 

Option 3. C