QUESTIONS

1. The table below shows how the gene for the human protein AAT (alpha-1-antitrypsin) can be inserted into sheep
Several mature eggs are collected from the ovaries of a  female sheep that has been given a fertility drug.

The eggs are fertilised in vitro.

A plasmid is prepared containing the gene for human AAT and a promoter sequence that causes the gene to be expressed in udder cells. Plasmids are microinjected into the nucleus of the fertilised zygotes. 

The zygotes divide in vitro until the embryos are at the 16-cell stage. The 16-cell embryos are implanted into the uterus of surrogate mother ewes. 

Test all the offspring from the surrogate mothers for AAT production in their milk. This is the only way to find if the zygote took up the AAT gene so that it can be expressed. About 1 in 20 eggs are successful.

Collect milk from the transgenic sheep for the rest of their lives. Their milk contains about 35 g of AAT per litre of milk.

(a) (i) What is the role of the plasmid in this process?

(1)

(ii) Why is the promoter sequence that causes the gene to be expressed in udder cells used?

(1)

(b) Describe how the AAT produced would be used to treat emphysema

(4)

(c) Name another disease that AAT could be used to treat

(1)