Gene Therapy Dr Hanan Hussien Shehata Explain What

Gene Therapy Dr. Hanan Hussien Shehata

Ø Explain What is a transgenic animal Ø Differentiate between Knockout, Knockin and Conditional Knockout (Knockin) animals Ø Identify the objectives of producing a transgenic animal. Ø Recognize three main ways to produce transgenic animals. Ø Mention the Problems faced when producing a transgenic animal. 3

What is a transgenic animal? A transgenic animal is animal whose chromosomes have been changed to carry the genes of other organisms.

Knockout animal A transgenic animal in which the normal gene is missing or engineered so that is not transcribed or translated. “Knocks out” that gen

Knockin animal A transgenic animal in which the engineered “transgene” is manipulated to: (A) alter the function of the gene (e. g. , replace one amino acid with another in a site to determine if that site is essential for the protein’s function); (B) change transcription rate to overproduce or underproduce the gene product; C) create a fluorescent gene product to map its distribution in tissue.

Conditional Knockout (Knockin) animal A transgenic animal in which the transgene is knocked out (or in) in specific tissues, at a specific developmental stage, or in response to an exogenous substance (e. g. , an antibiotic).

How are transgenic animals made? There are three main ways to produce transgenic animals: Microinjection Blastocyst injection Via retrovirus.

Microinjection: This involves injecting a transgene, the gene used to create a transgenic animal, into a fertilized egg. There is little ability to determine where the transgenic is located and whether it will survive. Because of this, most eggs do not survive or do not have the transgene, but between 1% and 30% of the eggs injected can produce a live transgenic animal.

Transgenic animals

Blastocyst Injection: This involves placing the transgene into an embryonic stem cell [ ES cell ]. ES cells are cells that are able to develop into all types of tissues. The cells are injected into blastocysts, which is an early stage of development. The injected ES cells become part of the animal and the animal becomes a mixture of transgenic and original cells.

Help of a Retrovirus: A retrovirus is a virus that can insert itself into a host’s chromosomes. This virus is inserted into the cells. The animals that contain the virus must breed to produce a transgenic animal.

Why are transgenic animals being made ? Transgenic animals are being made to help economic traits, traits be used as disease models, and help in medical research

Economic Traits: Scientists created cattle to produce milk containing certain human proteins which may help in the treatment of diseases as emphysema. It also helps in breeding. Farmers can produce transgenic animals that have the needed traits for doing a specific job.

Disease Models: Scientists are creating animals with specific human diseases and cancers, so that they can study the affects it has on the body. They hope this will help them find a cure for the different diseases and cancers.

Medical Research: Every year people die because of lack of a replacement heart, liver, or kidney. Transgenic pigs may be able to supply these organs. Research is trying to find a way to remove a pig protein and replace it with a human protein.

Problems: (a) Multiple insertions: too much protein. (b) Insertion into a life-necessary gene: lethality. (c) Insertion into a gene leading to genesilencing: no protein. (d) Insertion in a different area can lead to differential gene regulation.

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