How to knock out a gene - expert plaese answer?

Question

if we want to knock out a gene. do we need to do it in every cell. (a person get 1 trillion cells). each cell has a DNA copy.

or there is way to do it at once. And the DNA copy in every cell will be changed ,

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I asked same question again, because it is difficult to understand

Answer 1

You can't knock out a gene in a grown individual - there are too many cells. You can produce knockout lab animals by knocking out a gene in a single cell and then making it grow into a full sized mouse. Actually, what you do is inject the mutated cells in a number of mouse embryos; they will form part of their bodies. Then you mate these mice among themselves, because at least some of them will have the knocked out gene, but in heterozygosity; by mating them, you recreate homozygosity.

The use of report sequences throughout the process helps you figure things out.