2006-12-26 23:23:07 · 8 answers · asked by Heather 1 in Science & Mathematics ➔ Biology
Indentical twins: two sperms fertilize on egg at the same time.
Fraternal twins: two sperms fertilize two eggs at approximately the same time.
2006-12-26 23:24:58 · answer #1 · answered by regerugged 7 · 2⤊ 1⤋
Identical twins come from 1 egg that divided into 2. Non-identical twins come from 2 seperate eggs.
2006-12-26 23:25:39 · answer #2 · answered by lou b 6 · 1⤊ 0⤋
Do you mean by gender? If so, then it is because when a man's sperm fertilizes a woman's egg, the egg can split into two different zygotes producing fraternal twins, meaning twins that are different sexes. The other is when the sperm fertilizes the egg and the egg has two zygotes inside of it, that's identical twins, meaning twins that are the same sex.
2006-12-27 05:56:47 · answer #3 · answered by jjefferson210 2 · 0⤊ 0⤋
Identical Twins (also known as Uniovular or Monozygotic twins).
During the fertilization process, only one ovum is impregnated by only one spermatozoid, but the egg divides in 2 embryos afterwards. They have exactly the same chromosomes, they have a perfect resemblance and they have the same sex.
There are 3 different ways that identical twins can develop and be carried:
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With the first case there is only one placenta that feeds the babies, but there can be two amniotic sacs (as in the diagram at the side). When there is 1 placenta and 2 amniotic sacs then the pregnancy is referred to as having a "mono-chorial" placenta and is "bi-amniotic".
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In the second scenario, there is only one amniotic sac. In the case of 1 placenta and 1 amniotic sac then the pregnancy is referred to as having a "mono-chorial" placenta and is "mono-amniotic".
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The third scenario is where there are two placentae and each embryo has its own amniotic pocket. When there are two placentas and two amniotic pockets like this, then one speaks of a "bi-chorial" pregnancy that is "bi-amniotic". (This last case is an identical situation to fraternal twins as shown below).
Non-Identical Twins (also known as Fraternal, Binovular or Dyzygotic twins).
When twins are non-identical, then two seperate eggs have been impregnated by 2 separate spermatozoa.
They each have a different chromosome make-up, they don't look alike and they can be either the same or different sex. In fact, this is simply two separate pregnancies that just happened to occur at the same time.
Each embryo is in its own amniotic sac and has its own placenta. This type of pregnancy is referred to as "bi-chorial" and "bi-amniotic".
2006-12-26 23:26:13 · answer #4 · answered by Yellow Tail 3 · 2⤊ 0⤋
During ovulation an egg is released. If the egg splits into two and tow embryos develop then identical twins are formed. If two separate eggs are released at ovulation, then fraternat (non identical twins) are formed.
2006-12-26 23:34:52 · answer #5 · answered by Grace St. Andrew 2 · 0⤊ 0⤋
identical twins come from 1 egg that divided in 2 parts but
non-identical twins come from seprate eggs and in 2 conditions each one had a diffrent sperm and because that they may not be completely samae ( all cromzoms not same)
2006-12-26 23:38:43 · answer #6 · answered by Thomasian 2 · 0⤊ 0⤋
Indentical twins: one sperms fertilize on egg at the same time, but the embryo split to two with unknown reason. must be same gender, 2 males or 2 females.
Fraternal twins: two sperms fertilize two eggs at approximately the same time. can be 2 males, 2 females or 1 males and 1 females.
2006-12-27 01:37:08 · answer #7 · answered by chenho 3 · 0⤊ 0⤋
identical and fraternal twins. boys and girls are usually fraternal but the ones that look identical are identical, i think
2006-12-26 23:29:17 · answer #8 · answered by notre1842dame 4 · 1⤊ 1⤋