BIO372H5 Lecture Notes - Lecture 9: Mobile Genetic Elements, Dna Replication, Transposable Element
Document Summary
Some genetic elements move to new chromosomal locations by transposition. Mobile genetic elements (dna sequences) are called transposable elements ( transposons ). Specific dna regions moved to non-specific location in a chromosome. There are three principal classes of transposable elements. 1) dna transposons remain as dna throughout a cycle of recombination. 2) virus-like retrotransposons and 3) poly-a retrotransposons. Move to a new dna location using a transient rna intermediate. Generates 3"-oh group, which attacks target dna. Only one strand is transferred into the target dna. Two dna branches have a replication fork. Dna replication proteins assemble at these forks. The transposon dna is not excised from the host (donor) dna. Dna synthesized in the 5" to 3" direction. 1) dna transposons carry a transposase gene, flanked by recombination sites encoding transposases (recombinase for transposition) Terminal inverted-repeat sequences (recombination sites, ~25 bp) a gene. Additional genes e. g. , gene resistant to antibiotic.
