MBG Part Two: Lecture 14

Question 1

What is a major difference between HBR and NHEJ repair mechanisms?

Answer 1

HDR requires enzymes to direct strand invasion, while NHEJ does not

Question 2

In nucleotide excision repair what happens?

Answer 2

The DNA is first separated, followed by removal by helicase, and sealed by ligase

Question 3

Ionizing radiation leads to dimerization of pyrimidine bases. Which mechanisms can the cell use to repair this mutation?

Answer 3

Direct Repair, Nucleotide Excision Repair

Question 4

If depurination is detected, what repair mechanism would the cell use to fix it?

Answer 4

Base Excision Repair

Question 5

What are Transporable Elements?

Answer 5

Segments of DNA capable of moving from one location in a chromosome to another

Question 6

What is the LINE transposon estimated to undergo?

Answer 6

Every 1 transposon in every 100 births

Question 7

What do transposable elements lead to?

Answer 7

Chromosome breakage and insert in new locations

Question 8

What can bacterial transposons carry?

Answer 8

Antibiotic Resistance Genes

Question 9

What type of breaks do transposable elements make?

Answer 9

A staggered break

Question 10

Where do transposable elements ts attach to?

Answer 10

Single Stranded ends of DNA

Question 11

Where is DNA replicated?

Answer 11

At the gaps

Question 12

What are Flanking Direct Repeats?

Answer 12

3 -12bp long and generated in the process of transposition but do not belong to the transposable element

Question 13

What is the transposase enzyme?

Answer 13

Makes the staggered break in the DNA and catalyzes the transposition

Question 14

What are Terminal Inverted Repeats?

Answer 14

9 - 40 bp long, inverted and complimentary and found at the ends within many transposable elements

Question 15

What are Class I: Retrotransposons?

Answer 15

RNA is transcribed from the transposable element (DNA)

The DNA copt us made from RNA by reverse transcription and inserted into a new chromosome site.

Question 16

What does Retrotransposons require?

Answer 16

A reverse transcriptase - reverse flow of genetic material from RNA to DNA

Question 17

What does Class II: DNA transposons-catalyzed by transposase consist of?

Answer 17

1. Non Replicative Transposons
2. Replicative Transposons

Question 18

What are Non-Replicative Transposons?

Answer 18

Element is physically cut out of one site in a chromosome and pasted into new site (cut and paste), the number of transposable elements is preserved (no replication)

Question 19

What are Replicative Transposons?

Answer 19

Element is replicated with one copy and inserted at a new site (copy and paste leading to the number of transposable elements increasing)

Question 20

What does Class II DNA Transposition not require?

Answer 20

An RNA intermediate

Question 21

What types of transposons are in Eukaryotes?

Answer 21

Retrotransposons and DNA transposons

Question 22

What types of transposons are in Prokaryotes?

Answer 22

DNA transposons

Question 23

What mechanisms are in place to control or limit transposition?

Answer 23

DNA methylation
- Suppresses transcription
- Prevents the production of transposase enzyme

Alterations in Chromatin Structure to prevent transcription

Control of Transposase Translation by piRNAs

Question 24

What type of mutation is transposition?

Answer 24

A spontaneous mutation causing insertion (loss of function or gain of function)

Question 25

What does Transposition Lead to?

Answer 25

Duplications, Deletions, Insertions and Translocations

Question 26

How is Transposable Elements shown within a grape mutation?

Answer 26

Black Pigments in grapes (controlled by TF VVmybA!)

A retrotransposon insertion Gret1 disrupted gene resulting in white grapes

Red grapes came from a partial removal of retrotransposon which resulted in an intermediate

Question 27

How can deletion occur?

Answer 27

Pairing of direct repeats

Question 28

How can inversion occur?

Answer 28

Pairing of Inverted Repeats

Question 29

What can a misalignment of transposable elements on sister chromatids cause?

Answer 29

• Insertion or Deletion
• Translocation
• Duplication in other sister chromatid