Biology ~genotype and identical twins 20~~~

identical twins (also called monozygotic twins) are formed by fertilization from 1 sperm to 1 egg, turning into 1 zygote, and dividing into 2 embryos.
So, YES. they have the same DNA.

however, their appearance, traits may not be the same due to environmental influence. certain genes will switch on/off according to the different environment that the twins are in. so, as the twins age, the number of differences increases.
So, NO. their fingerprints are usually not the same due to environmental influence

2008-01-24 15:29:06 補充：
source: 2 years of BIO lectures labs.

2008-01-26 02:39:49 補充：
*fertilization of 1 sperm and 1 egg*

CE 的BIO:
應該只係會講 identical twins
係DNA 一樣的...
指模都會一樣

因為佢地係由同一條精子和卵子組成的合子分出來的...
所以佢地會有一樣的基因...
由遺傳基因決定的就會係一樣...
如血型, 基因上的缺陷,指模, 瞳色, 髮色等...

如果係同卵雙胞胎，DNA會非常接近，但不會完全相同。因為DNA在細胞分裂的時候都會有產生變異的機會。由一個受精卵分裂至一個完整的胚胎，中間需要經過很多次細胞分裂，所以雙胞胎之間仍然會有輕微的差別。同理，手指模也是獨一無二的，所以也不可能有完全一樣的手指模，故能用於身份辨認。