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Question
Explain the different types of twins in detail.
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Solution
Fraternal Twins
a) Fraternal Twins (commonly known as "non-identical twins") usually occur when two fertilised eggs are implanted in the uterine wall at the same time that is when the mother releases two eggs and both become fertilized by two different sperms.
b) The two eggs form two zygotes and these twins are therefore also known as dizygotic.
Dizygotic twins like any siblings have a very small chance of having the exact same chromosome profile.
c) but most likely have a number of different chromosomes that distinguish them.
d) Dizygotic twins may be a different sex or the same sex just as with any other siblings.
Like singleton siblings. they share 50% of their DNA.
Identical Twins
a) Identical Twins occur when a single egg is fertilized by a single sperm to form one zygote (monozygotic) but the zygote then divides into two separate embryos.
b) The biological mechanisms that prompt the single fertilized egg to split in two remain a mystery.
The two embryos develop into foetuses sharing the same womb.
c) Depending on the stage at which the zygote divides, identical twins may share the same amnion (in which case they are known as monoamniotic) or not (diamniotic).
d) Diamniotic identical twins may share the same placenta (known as monochorionic) or not (dichorionic). All monoamniotic twins are monochorionic.
a) Fraternal Twins (commonly known as "non-identical twins") usually occur when two fertilised eggs are implanted in the uterine wall at the same time that is when the mother releases two eggs and both become fertilized by two different sperms.
b) The two eggs form two zygotes and these twins are therefore also known as dizygotic.
Dizygotic twins like any siblings have a very small chance of having the exact same chromosome profile.
c) but most likely have a number of different chromosomes that distinguish them.
d) Dizygotic twins may be a different sex or the same sex just as with any other siblings.
Like singleton siblings. they share 50% of their DNA.
Identical Twins
a) Identical Twins occur when a single egg is fertilized by a single sperm to form one zygote (monozygotic) but the zygote then divides into two separate embryos.
b) The biological mechanisms that prompt the single fertilized egg to split in two remain a mystery.
The two embryos develop into foetuses sharing the same womb.
c) Depending on the stage at which the zygote divides, identical twins may share the same amnion (in which case they are known as monoamniotic) or not (diamniotic).
d) Diamniotic identical twins may share the same placenta (known as monochorionic) or not (dichorionic). All monoamniotic twins are monochorionic.
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