Genes Flashcards
(95 cards)
What are Chargaff’s Rules?
- # of A = # T (same for C&G)
2. # of A + T and C+G are equal on both strands
What is azidothymidine? (Zidovudine)
- Anti-Viral Drug
- Incorperation of nucleotiees that lack 3’-OH
- Used to treat HIV
Why doesn’t azidothymidine hurt humans?
- Human polymerase prefers Thymidien
- Viral Polymeraase prefers azidothymidine (AZT)
What is methylated in DNA?
- A & C nucleotides
- Histones
What keeps the two strands of DNA separate during replication?
-Single-stranded DNA binding proteins
What replaces the RNA primer in DNA replication?
-DNA polymerase I
What is Gyrase?
-The bacterial equivalent to topoisomerase
What drug targets Gyrase?
-Floroquinolones
Ciprofloxacin
How do Floroquinolones work?
Inhibit bacterial gyrase, causeing cell death
How does a cell identify DNA damage?
Repair enzymes continuously scan DNA strands for alterations in Tertiary structure of DNA or bulges, nicks in the phosphodiester bonds of the backbone, loops, double stranded breaks
Which enzymes are involved in DNA repair?
- Nucleases remove the damaged region
- DNA polymerase replaces the nucleotides
- DNA ligase seals the PDE bond
What is the role of p53 in DNA repair?
- It stops DNA replication until DNA is repaired
- Activates/sustains DNA Repair complexes
- Induces apoptosis if DNA Repair is not possilbe
What is a genetic disorder in which the DNA repair enzymes are damaged?
Xeroderma pigmentosum
How does Ionizing radiation damage DNA?
It affects sugar-phosphate backbone, leading to strand breaks-It damages purine rings
How does UV light damage DNA?
Causes dimerization between adjacent C and T bases
How do repair enzymes know which strand of DNA is the parent strand?
The parent strand is usually more methylated
What’s the difference between Exonucleases and Endonucleases?
- Exonucleases cleave 1 nucleotide from the end of a strand
- Endnonucleases cleave DNA at the middle of the strand
What enzyme is used to treat Cystic Fibrosis?
Dornase
What is homologous recombination?
The crhomosomal copy serves as a template so that its homologue can be repaired
Which type of cells contain telomerase?
Stem cells
What happens if a mature cell acquires telomerase?
Cancer
What is senescence?
Biological aging. Since DNA damage cannot be repaired, the cell stops dividing. The cell will go through apoptosis or will be eliminated by the immune system
What is the Hayflick Limit?
The point at which a cell can no longer divide, happens after ~50 divisions.
Why is RNA less stable than DNA?
- Single Stranded
- 2’ OH makes RNA more prone to hydrolysis