What are the events which lead to the formation of (a) identical twins, and (b) fraternal twins?
1 Answer
Fraternal twins occur when the female produces two eggs and identical twins occur when the female produces one egg and the zygote spontaneous divides into two.
Explanation:
Identical twins:
- In this case, the zygote undergoes cleavage(cell division by mitosis) when embryo is at two-celled stage.
- The two blastomeres may separate and then each behave as an independent zygote.
- Thus each broken blastomere give rise to a new independent individual.
- As both the organisms are produced as a result of mitosis, both have identical genetic makeup and are called identical twins.
- These twins involve sort of asexual reproduction after the normal sexual reproduction.
- Identical twins can't be of different genders. Mean both will be either males or females.
Fraternal twins:
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In some exceptional cases, the female produces more than one eggs.
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All eggs are independently fertilized by sperm.
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So, they form two or more zygotes. Each zygote develops into a new offspring.
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These offspring have different genetic combinations.
They may be two or more than two. Such offspring are called fraternal twins or triplets. -
They are produced sexually.
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Fraternal twins can have different genders as they don't have same genetic recombination.