MBLG2972 Lecture Notes - Lecture 14: Karyotype, P Element, Reverse Transcriptase
5 Jul 2018
School
Department
Course
Professor
MBLG2072
Genetics and Genomics
Monica Zanuttini !
460381099
Lecture 14 "Mobile genetic elements
Transposable genetic elements: !
Many forms, lengths, copy numbers, move via transposition. Can cause a mutation via insertional
inactivation. !
!
McClintock’s maize experiments show that the colourless
sectors had a terminal deletion of one chromosome 9
homologue. There was a dissociation (Ds) element causing this
chromosome breakage, along with activator (Ac). !
!
Unstable mutants had varied patterns of purple spotting, due to
insertion of Ds into the C lock (different spot to before)
producing a colourless kernel. This is a rare transposition of Ds
out of the gene. !
Transpositional elements require enzyme transposase. !
There are autonomous transposable elements: can catalyse their own movement as they have the
transposes gene needed to carry out transposition. !
Non-autonomous transposable elements: don’t carry the transposase gene, and is unable to
move unless transposase element is elsewhere in the genome.!
McClintock's transposable genetic element hypothesis was that the unstable mutant phenotype
resulted when a transposable element (Ds) created a mutation by its insertion into the C allele and
led to reversion when the expression of Ac led to its removal. !
Document Summary
Many forms, lengths, copy numbers, move via transposition. Mcclintock"s maize experiments show that the colourless sectors had a terminal deletion of one chromosome 9 homologue. There was a dissociation (ds) element causing this chromosome breakage, along with activator (ac). Unstable mutants had varied patterns of purple spotting, due to insertion of ds into the c lock (di erent spot to before) producing a colourless kernel. This is a rare transposition of ds out of the gene. There are autonomous transposable elements: can catalyse their own movement as they have the transposes gene needed to carry out transposition. Non-autonomous transposable elements: don"t carry the transposase gene, and is unable to move unless transposase element is elsewhere in the genome. In bacterial genomes there are two categories of transposable elements: Is (insertion sequence) elements: contain only genes and sequences needed for autonomous transposition. About 1000 bp of dna, followed by an inverted repeat (ir) sequence.
