In this series of ten blogs, various parts of the GCSE Science, IGCSE Biology specifications will be explored through the context of food. As well as assisting students revising for their GCSE and IGCSE exams, the blogs also provide an every-day context for science which all readers should find accessible, interesting and useful.
Lamb chops for dinner tonight! Whether you keep sheep yourself or buy your chops from a farm shop, butcher or supermarket; whether they are produced in the UK or New Zealand, almost all sheep are kept outside and eat lots of grass. Sheep have been shaping the land in the UK for millennia. Their grazing creates short-grass conditions favoured by many of our beautiful native wild flowers, and sheep thrive in areas where crops cannot be grown and where the nutritional content of the land is too poor for other farm animals.
There are many breeds of sheep in the UK; the first to arrive was a domesticated Neolithic variety similar to Soay sheep which still survive today; other breeds were brought from mainland Europe in more recent history. From earliest times, farmers selected which sheep in their flocks had desirable characteristics and bred from them. Those desirable characteristics, whether in the meat, wool or hardiness were passed on to the lambs. Over generations, this artificial selection caused different varieties of sheep to be found in different parts of the country. Today the varieties of our native domestic sheep are protected – examples are Portland and Teeswater – and they are very different from the original Soays.
With new technology, new methods for producing sheep with desirable characteristics have developed. Sheep have been both genetically modified and cloned for research purposes; medical products are the most common research area. Neither process is used commercially in farms.
One method of genetic modification of sheep involves inserting genes from another organism into a sheep cell whose nucleus will be inserted into a sheep’s egg. The developing embryo and resulting lamb then carries extra genes.
Cloning – first done with sheep in the UK producing Dolly – involves inserting a complete nucleus from an adult sheep cell into an egg cell whose own nucleus has been removed. The resulting egg, given an electric shock, will start to divide and, in a few cases, sucessfully become an embryo resulting in a live birth. The lamb is genetically identical to the sheep from whom the nucleus was taken.
Next time lamb chops are on the menu, consider how far the sheep has come in 6000 years and how it has been shaping our lives throughout this time.
Science Tutor OOL