Analyzing and Engineering Genes

Analyzing and Engineering Genes - Chapter 19: Analyzing and...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 19: Analyzing and Engineering Genes I. The Effort to Cure Pituitary Dwarfism: Basic Recombinant DNA Technologies The Pituitary gland is a structure at the base of the mammalian brain that produces several important biomolecules, including a protein that stimulates growth. This protein was named human growth hormone (HGH). The gene that codes for it is called GH1. a. Why Did Early Efforts to Treat the Disease Fail? Physicians began treating the disease with injections of naturally produced growth hormone. 1. Early trials showed that people with pituitary dwarfism could be treated successfully with growth hormone therapy, but only if the protein came from humans. 2. The only source of HGH was pituitary glands from human cadavers. 3. When some of the children treated with HGH developed a prion disease in their teens and twenties, physicians realized that the supply of growth hormone was contaminated with a prion protein from the brains cadavers supplying the hormone. The use of growth hormone isolated from cadavers was banned. b. Steps in Engineering a Safe Supply of Growth Hormones 1. Their plan was t insert fully functional copies of human GH1 into E.coli, which they hoped would then produce huge quantities of recombinant progeny. The recombinant cells would produce uncontaminated growth hormone in sufficient quantities to meet demand at an affordable price. ii. Using Reverse Transcription to Produce cDNAs 1. An enzyme called reverse transcriptase is responsible for a major exception to the central dogma of molecular biology: It allows information to flow from RNA to DNA. More specifically, reverse transcriptase catalyzes the synthesis of DNA from an RNA template. 2. DNA that is produced from RNA is called cDNA. 3. Reverse transcriptase played a key role in the search for the growth hormone gene. Knowing that GH1 is actively transcribed in cells from the pituitary gland, researchers isolated mRNAs from pituitary gland cells and used reverse transcriptase to reverse-transcribe those mRNAs to cDNAs. iii. Using Plasmids in Cloning 1. The effort to produce many copies of a gene is referred to as DNA cloning. Researchers can clone a gene by inserting it into a small, circular DNA molecule called a plasmid. 2. Some plasmids carry genes for antibiotic resistance or other traits that increase the cell’s ability to grow in a particular environment. 3. If researchers could splice a loose piece of DNA into a plasmid and then insert the modified plasmid into a bacterial cell, the engineered plasmid would be replicated and passed on to daughter cells as the bacterium grew and divided. 4. When a plasmid is used in this way – to make copies of a foreign DNA sequence – it is called a cloning vector. 5.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/16/2011 for the course BIO 180 taught by Professor Chamberlain during the Spring '08 term at Staten Island.

Page1 / 4

Analyzing and Engineering Genes - Chapter 19: Analyzing and...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online