Lecture 22 - Mobile genetic elements

Question 1

What are 3 different types of mobile genetic elements?

Answer 1

Plasmids, viruses, transposons

Question 2

Describe the structure of plasmids and how they are mobile

Answer 2

Plasmids: small circular DNA, don’t usually integrate into host genome (but can), use host machinery to propagate, encodes functions that impart advantage to host
Can go from one cell to another through conjugation, where F-pilus brings membranes together

Question 3

Describe the structure of viruses, and how they are mobile

Answer 3

Viruses: very small, uses host cell machinery to reproduce, will lyse cell
Has protein coat (protects nucleic acid), nucleic acid (genome), nucleoprotein (packages genome)
Can be in either lytic or lysogenic life cycle: Lytic cycle the genome circularizes, doesn’t integrate, synthesizes new virions and lyses cell
Lysogenic: genome integrates into host, replicates normally, when recombination event occurs, prophage enters lytic cycle

Question 4

What are transposons?

Answer 4

mobile DNA particles that jump from site to site on the chromosome. Transposons encode for transposases, tightly regulated and occurs infrequently
Random, can be lethal for cells, but another way to diversify genetic diversity

Question 5

Describe the 2 types of transposons

Answer 5

Direct: transposase cuts out tranpsosons by recognizing certain inverted repeating segments, cuts asymmetrically at target site and inserts transposon, then gaps covered through replication
Replicative: two sites form co-integrate, covalently bonded, then transposon replicated and integrated, then dissociation of protein