Raz I：Two Make Twins

跟著小妞學(xué)英語(yǔ)之人體篇，收集資料如下。問(wèn)了我好多千奇百怪的問(wèn)題…

• Identical Twins：identical twins occur when a single egg is fertilized to form one zygote which then divides into two separate embryos.
  • Monozygotic twins are genetically nearly identical and they are always the same sex unless there has been a mutation during development.
  • Fingerprints are patterns on the tips of your fingers. Identical twins can look very alike, but their fingerprints are always different.
• 同卵雙生（identical twins）
• Fraternal Twins:When two eggs are independently fertilized by two different sperm cells, fraternal twins result. ---This is the most common type of twin.
  • Fraternal twins are, essentially, two ordinary siblings who happen to be born at the same time, since they arise from two separate eggs fertilized by two separate sperm, just like ordinary siblings.
• 異卵雙生（non-identical twins/Fraternal Twins）
  • 女性通常每一次月經(jīng)里，卵巢只釋放一顆卵子，但偶爾可能一次釋出兩粒卵子，兩顆卵子同時(shí)各自受精后各自所形成的兩粒受精卵能同時(shí)發(fā)育成兩個(gè)獨(dú)立胚胎，此稱為異卵雙生其中的遺傳基因信息是各有各的一套，性別搭配可以相同也可以混搭，如此雙生其實(shí)相當(dāng)于普通親生手足，往往不太像。