RECOMBINANT DNA AND GENOMES Molecular cloning vs cellular like Dolly copies of 1 gene at a time Genetic engineering making using recombinant DNA discovery of 2 very important things small circular DNA molecules called plasmids that replicate in bacterial cells especially prevalent in resistant microbes enzymes that cut double stranded DNA at specific nucleotide sequences along with DNA ligase these 2 things make it possible to recombine DNA restriction enzymes molecules in the lab 2 sets of DNA molecules combined recombinant DNA molecule restriction enzymes make staggered cuts in the vector DNA sticky ends small regions of single strands that can base pair with their complimentary sequences restriction sites are often palindromes DNA ligase used to make covalent bonds between insert DNA and vector DNA transformation insertion of recombinant DNA into cells selection only cells that have received a plasmid can grow in the presence of the antibiotic plasmid contains a selectable marker libraries collections of recombinant DNA genomic libraries contain clones representing all of the DNA sequences in a genome each bacterial cell used to clone contains a different recombinant DNA molecule in some cases you would not want to clone genomic DNA contains introns only want the 1 5 expressed you would make cDNA starting with mRNA from a specific organ or tissue reverse transcriptase special DNA pol from retroviruses to copy mRNA to DNA once cDNA is double stranded by a regular DNA pol it can be cloned into vectors clones represent genes that are expressed recombinant DNA molecules can be introduced into plants and animals GMO or transgenic organism contains recombinant DNA concerns about GMOs consumption exposure could cause allergic reactions or toxicity insect resistance could kill both helpful and destructive species are we making transgenic humans gene therapy is a transient kind of genetic modification recombinant DNA does not become part of the genome Human genome 1 5 exons giving rise to proteins rRNA or tRNA 300 bases introns 3000 bases GENOMES