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- In agricultural settings, because freemartins can’t reproduce, farmers often identify them through physical and/or behavioural traits.
- 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.
- 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).
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.
Option 3. C