Repetitive DNA Part 4 Flashcards Preview

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Flashcards in Repetitive DNA Part 4 Deck (29):
1

Transposition

- moves mobile genetic elements between non homologous sites in the genome

1) to different places within one chromosome
2) between 2 chromosomes

2

what is responsible for a large fraction of the evolutionary change in a genome

- mobile elements

3

each mobile element contains

- an enzyme that mediates its own movement - transposase
- special sites upon which the enzyme acts - to mobilize the transposons

4

transposons

- transposable elements

5

mobile genetic elements target site selectivity

- have only little target site selectivity therefore move freely throughout the genome

6

transposase acts on specific DNA sequence at the end of transposon

- disconnects transposon from flanking DNA
- inserts it into new target DNA site
- no requirement for homology
- most move only rarely

7

3 classes of transposons

- DNA transposons
- LTR-containing transposons
- non-LTR retrotransposons (non autonomous retrotransposons)

8

wild type maize

- C locus expressed

9

Mutated maize

- transposable element ds is inserted into C locus and knocked out its expression

10

reverted maize

- Ac acts upon Ds element to jump it out in some cells to restore color

11

which element is more active

- Ac element more active than Ds element

12

Ac transposon

- has full transposon
- has transposase
- inverted repeats

13

transposase acts on Ds

- to move them but they can't move themselves

14

original mutation

- result of transposable element in C gene
- DS

15

another transposable element

- Ac = activator
- induces Ds to transpose out of C, causing reversion

16

Ds can transpose, but

only with the help of Ac

17

Ac autonomous transposon

- can transpose itself and inactivate other Ds genes by itself

18

DNA transposons move in the genome by

- cut and paste mechanism

19

two pathways of cut and paste transposons

- replicative
- nonreplicative

20

replicative

- copy self and leave old copy in place
- 2 copies now

21

nonreplicative

- jumps from one place to another

22

retrotransposons

- move by copy and paste mechanism

23

copy and paste

- makes RNA intermediate that must be reverse transcribed into DNA before being inserted into the genome

24

LTR-containing retrotransposons

- similarities with retroviruses
- AIDS virus, HIV infects human cells

25

how HIV replicates

- take viral RNA and using host nucleotides converts viral RNA into ssDNA then transcribed into dsDNA

26

non-LTR retrotransposons

- movement requires reverse transcriptase
- move by a copy and paste mechanism

27

types of non-LTR retrotransposons

- LINEs
- SINEs

28

80% of maize genome

- retrotransposons

29

half the genome of humans is composed of

- repetitive DNA