Artifical Selection

1. Artifical Selection

2. Artificial Selection • Artificial selection is the deliberate selection of organisms with desirable characteristics that are useful to humans • Humans determine which alleles pass onto successive generations.

3. Selective breeding • Useful varieties of plants and animals have been derived from species by selective breeding

4. Selective breeding • Cattle have been bred for • Quantity and quality of meat • Milk yield • Butterfat content of milk • Plants • Increasing yield of crops • Disease resistance

5. Inbreeding depression • Reduction in variation of alleles in the population • Increase risk of homozygosity (harmful recessive genes)

6. hybridisation. • Hybrid • Individual resulting from a cross of two genetically dissimilar parents of the same species • Hybrid vigour – some offspring produced are stronger (“fitter”) than either parent. • Re-establishes heterozygosity.

7. Hybridisation in Farm Animals • Hybrid vigour in cattle • Improved birth weight • Improved feed conversion efficiency • Sheep • Scottish blackface x French strain • Hybrid has improved meat yield and quality

8. Genetic Engineering

9. Genetic Engineering(Recombinant DNA technology) • Genome haploid set of chromosomes typical of a species • Recombinant DNA technology involves transferring genes from the genome of one organism to the genome of another.

10. Location of genes • Recognition of characteristic banding patterns on chromosomes • Giant chromosomes take up stains producing distinctive bands • Banding pattern is a constant characteristic of each type of chromosome • Example – red/white eye colour in fruit fly • Gene probes • Short length of chemically labelled single sided DNA • Complementary to the gene that the genetic engineers wish to locate • DNA is cut into fragments and the gene probe attaches to required gene

11. Genetic Engineering • Select a gene for desirable characteristics • Select a suitable vector • Splice the gene into the DNA of the vector • Insert vector into host cell • Host cell propagated

12. Enzymes involved • Endonuclease • Used to cut DNA into fragments and open bacterial plasmids • Recognizes a particular sequence of bases on DNA and makes its cuts at these sites. • Ligase • Seals “sticky ends” • Seals DNA fragment into bacterial plasmid

13. Vector • Recombinant plasmids carry DNA from genome of one organism into that of another.

14. Antibiotic • Recombinant plasmid also contains a gene coding for anti-biotic resistance

15. Useful products • Insulin production • interferon • Human growth hormone production

16. Transgenic crops • Agrobacterium tumefaciens can inject a plasmid into plant cells, the plasmid’s genetic material can become incorporated into the plant’s DNA. • Scientists use this bacteria to insert desirable genes into plants. These plants are transgenic varieties. • e.g. gene inserted to produce an insecticide protein, the leaves of the plant can resist attack by caterpillars.

17. Crop plants • Other inserted genes in plants • block production of chemicals which promote ripening • resistance to weed killer • production of antifreeze chemical • block enzyme production • ability to fix nitrogen • resistance to drought

18. Farm animals • genetically modified to produce human proteins • Examples • blood clotting factor • Eggs that contain anti-bodies needed for cancer fighting drugs

19. somatic fusion • Somatic fusion allows a fertile hybrid to be formed from two species. • Protoplasts from two different species are prepared by having their cell walls removed. • These protoplasts fused to form hybrid protoplast. • Somatic hybrid cell is induced to form a cell wall • Hybrid cell divides into a callus (undifferentiated cell mass) • Calluses develop into hybrid plants containing mixture of parents’ genetic traits.

20. Resistance to potato leaf roll • Through somatic fusion a potato plant has been produced which is tuber bearing and resistant to potato leaf roll virus.