GENE KNOCK IN,KNOCK OUT &KNOCK DOWN INTRODUCTION

KNOCK IN - What it implies something is inserted.
KNOCK OUT - It indicates something is omitted
KNOCK DOWN -  Need to down or decrease some expressions.

GENE KNOCK  IN-- Its the opposite of knock down gene. A gene is inserted from outside  in a region to see the function and interaction .

Techniques used -
1.Site specific recombination
2.By using transposons 

GENE KNOCK OUT - It is a method of creation of transgenic animals .The first knockout mouse was created by Mario R,Martin Evans and Oliver in 1889 for which they were awarded with nobel prize on 2007. It is a long term process .

 What do each of the genes present in a body do? Geneticists studied this by inactivating, or “knocking out”, the corresponding gene in mice or other model organisms. Then they observed whether their is any difference from normal behaviour or not. 
Process involves knocking out (made inoperative) of both the alleles of a gene and replacing it with a artificial piece of DNA which is inactive. The apperance of change in any phenotypic signs implies the function of knockout gene. 
Knocking out 2 genes simultanoeusly is called DKO (Double knockout ).

Functions-  1.To know what exactly happens when a gene is absent or mutated.
              2. To study the role of genes which have been sequenced but have unknown function.
               

Techniques used -
1. In test tube with plasmid .                                      
2.By BAC(bacterial artificial chromosomes)
3.With cell cultures                               
4.Homologous recombination or gene targeting 
5.Introducing short sequences of lox-p sites around the gene.

Goal - To create a transgenic animal that have altered gene .


Image source credit-https://www.genome.gov/12514551/

GENE KNOCK DOWN - Idea is same need to ommit the expression of desired gene but not completely . Genes are present but they are blocked . It is not physically deleted we need to block only the expression . It can achived in few weeks .

Technique used- By RNAi 

NOTE-
A knockin model replaces an endogenous gene with a mutant gene, but leaves the original promoter region intact such that expression is controlled by normal regulatory mechanisms. Therefore, gene expression typically occurs at normal levels. 
Knockout models remove a gene from the genome, and thus do not increase levels of gene expression. 

MCQs.  - 
1.Homologous recombination can be employed to generate 
A.  transgenic animals
B. Gene knockout animals 
C. Site specific mutagenesis 
D. Specific promoter sequences
Ans.  B (GATE XL - 2005) 

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