A gene knock-in (or knock-in) refers to a genetic engineering method that involves the one-for-one substitution of DNA sequence information in a genetic locus or the insertion of sequence information not found within the locus. A gene knock-in therefore can be seen as a gain of function mutation and a gene knockout a loss of function mutation, but a gene knock-in may also involve the substitution of a functional gene locus for a mutant phenotype that results in some loss of function.

knock at/on 敲knock into 撞到某人身上knock down 撞倒knock out of 把…敲出knock over 撞倒knock off 停止工作，休息1) The boxer soon knocked his opponent ________ __.2) The office stuff knocks _________ ___ at six every day.3) Try knocking __________ ___ the window and see if there is anyone indoors.4) He was so absorbed in his book that he knocked __________ _____ the car parked there.

Suddenly he heard someone（）gently on the window. A: knock B: knocking C: knocked D: to knock

A: Listen! There__________ someone __________ at the door.B: It must be your sister. A: is; knocking B: is; knock C: are; knocking D: are; knock

Knock a total of ______ times. Each knock ______. A: one B: two C: three D: four E: five

There was a knock on the door, but _____ answered it.

Listen!Someone____________(knock)atthedoor.

knock out（基因敲除）

I heard someone _______ loudly at the door while I was listening to the radio. A: knock B: knocking C: to knock D: knocked

中国大学MOOC: “Knock off early” means ( ).