Recombinant DNA
Copying DNA Genetic engineers can transfer a gene from one organism to another to achieve a goal, but first, individual genes must be identified and separated from DNA. The original method (used by Douglas Prasher ) involved several steps:
- Determine the amino acid sequence in a protein.
- Predict the mRNA code for that sequence.
- Use a complementary base sequence to attract the predicted mRNA.
- Find the DNA fragment that binds to the mRNA.
Once scientists find a gene, they can use a technique called the polymerase chain reaction to make many copies.
- Heat separates the DNA into two strands.
- As the DNA cools, primers are added to opposite ends of the strands.
- DNA polymerase adds nucleotides between the primers, producing two complementary strands. The process can be repeated as many time as needed.
Changing DNA Recombinant DNA molecules contain DNA from two different sources.
Recombinant-DNA technollogy can change the genetic compossition of living organisms.
- plasmids are circular DNA molecules found inbacteria and yeasts; they are widely used by scientists studying recombinant DNA, because DNA joined to a plaemid can be replicated.
- A genetic marker is a gene that is used to differentiate a cell that carries a recombinant plasmid from those that do not.
Transgenic Organisms Transgenic organisms contain genes from other species. They result from the insertion of recombinant DNA into the genome of the host organisms. A clone is a member of a population of genetically identical cells.