How Are Identical And Non Identical Twins Formed?

Identical twins form when one fertilised egg splits in half. Each half has the same genetic makeup resulting in two boys or two girls that look exactly alike. They will share an embryonic sack and placenta. If the egg doesn't split completely in half conjoined twins will form. Conjoined twins will have a part or parts of their body connected together at the site where the egg did not split. Operations are needed to separate the twins unless they share vital organs. Non identical twins, known as fraternal twins, result from hyperventilation. Hyperventilation is when more than one egg is released. Most women only release one egg per cycle (each month), but some release more than one egg in a cycle. If two eggs are released in a cycle and both eggs get fertilised they will each have their own genetic makeup, different embryos sacks, and their own placenta. They are no different than two siblings being born at different times, only they share the uterus for nine months and have the same birthday. Hyperventilation is genetic, so if a woman's mother or grandmother has had fraternal twins, she or her daughter may have fraternal twins as well. Identical twins are not genetic and happen in random pregnancies.

Identical twins are formed from the same egg. During development, the egg and sperm will develop into two identical parts and begin to grow separately into two babies instead of  the usual one, they also share a placenta.

In non identical twins, there are two eggs that are both fertilised around the same time but they are completely separate. They each have their own set of chromosomes and their own placenta.

Non identical twins are two siblings who happened to be conceived together and to share the same pregnancy.    This is possible because mum released two ova or eggs at once( instead of the normal one egg , in humans). The tendency for this to occur can run in families.     Obviously the two eggs contain a different variety of genes and  are fertilised by two different sperm also obviously containing different varieties of genes. This means that the two embryos are no more closer genetically than  any two siblings conceived and born as singletons.  Therefore they can be two boys, two girls or one of each.

Two seperate eggs are fertalized by sperm.  In identical twims one egg is fertalised and splits into two.

Twins for when two egg cell are fertilizes each egg by a different sp ern so that two embryos are formed

Identical twins are formed from the same egg - during development the egg and sperm will divide into two identical parts and begin to grow separately into two babies instead of the usual one, they also share a placenta. In non identical twins there are two eggs that are both fertalized around the same time - but they are completely separate they each have their own set of chrmosomes and their own placenta.

Identical twins arise when the fertilised ovum splits into two and continues to form two identical embryos. They are clones of each other as they share the same genes.     Non identical or two egg twins are made when the mother sheds two ova at the same cycle and two separate sperm fertilise them. Two egg twins share the same 50 per cent genetic material as  would any 2 siblings  that are conceived at different times.

One sperm splits into two eggs which is equal to twins

Identical twins are formed when the fertilized egg splits into two,thus
developing into two separate fetuses.This would mean that identical
twins are always the same sex.

I liked the first answer everyone was else was just annoying trying to be smart :) sorry though

Non identical twins are formed when the ovary lets two eggs out at the same tim

With identical twins, there is only one egg fertilised which splits into 2 (sometimes more), babies. They will therefore be the same sex and identical in every way. in non-identical twins two eggs are fertilised, and they may be of different or the same sex and look no more alike than any other sibling.

Non identical twins are called Fraternal twins.
 
identical twins are formed when a zygote (the combo of egg and sperm) splits into two zygotes.
 
fraternal twins are made up of two different zygotes ( two different eggs matched with two different sperm)  

Thank you very much
you helped me on my science homework!!
I hope I get a Gd level on it !!!

Identical twins have the same face but non-identical twins do not have the same face

Simpiler answer:
 
Identical twins form when the fertilized egg or ovum splits in two, and two feotuses form.
 
Non identical twins form when two (or more) eggs are fertilized, and two feotuses form.

Identical twins are formed when one fertilized egg splits into two in the earliest stages of pregnancy. Non Identical twins are formed when two eggs are fertilized at the same time.
That is why Identical twins are always the same sex, but non identical can be different sexes.

•Identical twins are formed when one fertilized egg splits in half. Each half has the same genetic form resulting either

    2 boys/2 girls/1 boy & 1girl that look exactly the same. They will share an fluid filled sack and a placenta.

Identical twins come from 1 egg cell splitting

non identical twins are formed from 2 cells being at the womb and being fertilised at the same time

When the mother supplies two maternal cells instead of her normal one cell, each are fertilized individually and result in non identical twins, each with different DNA. Identical twins happen when one maternal cell is fertilized then divides into two distinct embryos which then continue to develop separately, each with identical DNA since they initially where a single fertilized cell.

I wold guess that they are much like twins

I bloody don't know

Identical  twice are made when an egg divides intom2.

Identical twins have two eggs instead of one and then the sperm fertillizes.

I have friends who are twins and they have different dads.  Shame on mommy, oops.