Chpt 28b Flashcards
Semiconservative synthesis
each parental strand serves as template for synthesis of a new complementary strand
DNA synthesis: Leading and Lagging strand
DNA is synthesize in the 5’ to 3’ direction
Leading strand- continuous synthesis
-goes into the replication fork
Lagging strand- discontinuous synthesis
-results in Okazaki fragments
DNA ligaase
Seals nicks
- synthesizes phosphodiester bond between the 3’ hydroxyl group at the end of one change and the 5’ phosphate group at the of the other strand of the dsDNA
- requires ATP for archaea and eukarya
- requires NAD+ for bacteria
Process of initiation of replication
1) DnaA protein binds
2) ssDNA exposed to prepriming complex
- helicase, SSB, Primase
3) Polymerase homoenzyme assembles
Trombone model of lagging strand synthesis
DNA poly III synthesizes about 1000 nucleotides per okazaki fragment
-as nucleotides are added the slide lengthens
Telomerase
Specialized eukaryotic reverse transcriptase
- synthesizes the linear ends of chromosomes (telomere)
- carries own RNA template
Telomere
Linear ends of chromosomes
- Humans have repeated seq AGGTTT repeat
- protect ends from nuclease digestion
- senesence aging
In vivo telomere structure
ss region of DNA invades and H bonds to telomere repeat sequence
-stabilized by telomere binding proteins
Telomerase Model
Elizabeth blackburn and Carol Greidor model
- Elongation
- Translocation
Reverse transcriptase
Retrovirus- Human immunodeficiency virus (HIV)
-RNA genome converts RNA into viral DNA which integrate into human genome
Reverse transcriptase inhibitors
Nucleoside analogues-chain terminators -Zidovudine (AZT) -2',3' dideoxyinosine (ddI) *didanosine Nonnucleotide analgoues Protease Inhbiitors
DNA repair
repair is done due to damage that occurs from various sources
