Wool Production

Three transgenic approaches have been investigated for enhancing wool production or improving wool quality. The first involved transfer of bacterial genes that had the capacity to synthesize cysteine from hydrogen sulfide and serine, both of which are available in the rumen. Cysteine is the rate-limiting amino acid for wool production, so an endogenous source of this amino acid has the potential to stimulate wool growth. The second approach to improve wool production was to stimulate fiber growth by expression of an IGF-I transgene specifically in wool follicles. The third approach was to improve wool fiber quality by altering expression of wool fiber keratin and

Table l Some proposed modifications of milk constituents

Change

Increase a and b caseins Increase phosphorylation sites in caseins Introduce proteolytic sites in caseins Increase k casein concentration

Eliminate b lactoglobulin

Decrease a lactalbumin

Add human lactoferrin Add human lysozyme

Add proteolytic sites to k casein

Decrease expression of acetyl CoA carboxylase

Express immunoglobulin genes

Replace bovine milk protein genes with human equivalents

Consequence

Enhanced curd firmness for cheesemaking, improved thermal stability, and increased calcium content

Increased calcium content, improved emulsification

Increased rate of textural development to improve cheese ripening

Enhanced stability of casein aggregates, decreased micelle size, decreased gelation and coagulation

Decreased high temperature gelation, improved digestibility, decreased allergenic response, decreased primary source of cysteine in milk

Decreased lactose, increased market potential of fluid milk, decreased ice crystal formation, compromised osmotic regulation of mammary gland

Enhanced iron absorption, protection against gut infections

Increased antimicrobial activity, reduced rennet clotting time, and increased cheese yield

Increased rate of cheese ripening

Decreased fat content, improved nutritional quality, reduced milk production costs

Protection against pathogens such as salmonella and listeria Mimic human breast milk keratin-associated protein genes in the wool follicle cortex.[9] Research on the latter approach is still underway in South Australia.

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