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Hereditary diseases. History of genetic engineering

Lessons 26–27 · 2 lessons · A. G‘afurov, A. Abdukarimov, J. Tolipova, O. Ishankulov, M. Umaraliyeva, I. Abdurahmonova. Biology, Grade 10, 1st edition. “Sharq” publishing and printing joint-stock company, Tashkent, 2017
27

Research objects and history of genetic engineering

Textbook: pp. 121–122
GoalExplain the concept of genetic engineering, its research objects and the main stages of its history.
New words
genetic engineering · gen muhandisligirecombinant DNA · rekombinant DNKelectrophoresis · elektroforeztransgenic organism · transgen organizm
Explanation

Genetic engineering is the purposeful modification of an organism’s genes for human benefit: a set of methods to isolate genes, insert them into another organism and create organisms with new hereditary traits (transgenic). Research objects are viruses, bacteria, fungi, and plant and animal cells. The science developed after the structure of DNA was discovered: in 1953 J. Watson and F. Crick proposed the double-helix model; in the 1960s–70s the genetic code was deciphered and enzymes that cut DNA (restriction enzymes) and join it (ligases) were found; in 1972 P. Berg obtained the first recombinant DNA; in 1973 S. Cohen and H. Boyer inserted a foreign gene into a bacterium; from 1977 methods of reading the nucleotide sequence (sequencing) appeared; in 1978 human insulin was obtained using bacteria; in 1996 Dolly, a cloned sheep, was born; in 2003 the Human Genome Project was completed; since 2012 CRISPR/Cas9, a method of precise genome editing, has spread widely. Electrophoresis separates DNA fragments by length, and PCR (polymerase chain reaction) makes copies of DNA. Genetic engineering is used in medicine, agriculture and industry; its safety and ethical questions are discussed as well.

Worked examples
If the insulin gene is inserted into a bacterial plasmid, the bacteria multiply and make human insulin. Insulin was once taken from animal organs; now it is produced cheaply and in large amounts with such bacteria and yeast.
In PCR the number of DNA copies doubles every cycle: in 10 cycles one molecule gives 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 1024 copies.
Class activity

“Timeline”: groups put the events (1953, 1972, 1978, 1996, 2003, 2012) in order and draw a timeline on a big poster.

Practice
1
Define genetic engineering.
2
Distinguish the functions of electrophoresis and PCR.
3
In PCR, how many copies come from one DNA molecule after 8 cycles? (Number only.)
4
Why are bacteria convenient objects in genetic engineering?