Chapter 4: 4.7 Repair of Double Stranded DNA Breaks Flashcards
True or False:
Double-stranded breaks in DNA are not too damaging
False, they are particularly damaging
Why are double-stranded breaks in DNA particularly damaging?
Incorrect joining of the strands cause mass reorganization of the genes and affect the structure of chromosomes
List:
Methods of Repair of DNA Strand Breaks
- Non-Homologous End Joining
- Homologous Recombination
Describe:
Non-Homologous End Joining (NHEJ)
Joins two non-homologous ends of DNA together
* Usually after a double stranded break, the two ends of DNA are still close enough together that they will be ligated back together
What are the issues with NHEJ?
- Causes minor deletions; base pairs from either ends of the DNA fragments are lost
- Genes can end up joining together (chimeric genes)
True or False:
Deletions from NHEJ and harmful
False, they are usually not as the majority of DNA is non-coding or intronic DNA
Define:
Chimeric genes
Genes that are joined together
* Can result in changes to cell function or cancer
Describe:
Homologous Recombination
- Damaged DNA sequence is copied from an undamaged or highly similar (homologous) copy of the DNA
- The break is repaired by an exchange of two different DNA strands, referred to as recombination
What can homologous recombination be used to repair?
- Repair nicks in replication forks
- Double stranded breaks in DNA
True or False:
Homologous Recombination is error free
True
In Homologous Recombination:
How many different outcomes are there?
4 different outcomes
* The Holliday structure can be resolved in two different ways, yielding two different produces
* Thus double stranded breaks yield 4 different outcomes
True or False:
Homologous recombination is involved in genetic diversity of the offspring
True, provides a mechanism for creating genetic diversity
