(BIO) DNA Replication Flashcards
DNA Polymerase (Base Pairing)
Leading strand –> DNA pol (delta)
Lagging strand –> DNA pol (alpha)
Adds new nucleotides one at a time by extending the 3’ end of existing nucleotide chain, creating new phosphodiester bonds
DNA Ligase
Catalyzes the joining of DNA strands via formation of phosphodiester bonds
Used in:
- DNA replication (lagging strand)
- DNA repair
DNA Helicase
Motor protein
Moves along the phosphodiester backbone
Breaks hydrogen bonds between annealed nucleic acid strands
DNA Primase
Enzyme
Produces a short RNA primer that DNA polymerase can elongate when initiating synthesis of a new DNA strand
DNA polymerases cannot initiate DNA synthesis without an initial RNA or DNA primer
Topoisomeraase
Guides the unwinding of DNA by creating transient breaks in the DNA to relieve supercoiling
Leading strand
The 3’ to 5’ parent strand
Complementary DNA is synthesized continuously (b/c new nucleic acids can only be created in 5’ to 3’ direction)
Lagging strand
The 5’ to 3’ parent strand
Complementary DNA made in short fragments
Okazaki Fragments
Short DNA fragments synthesized on lagging strand
Each fragment is built 5’ to 3’
Each fragment requires a new RNA primer
Fragments must be joined together by DNA ligase
RNA Primer
A 7 to 10 base pair long nucleic acid sequence that serves as a starting point for DNA synthesis
Produced by Primase
SSBs
Single Stranded Binding proteins
Bind to DNA and prevent the parent strands from re-annealing into dsDNA
DNA
- Nitrogenous bases: ATGC
- Deoxyribose as its 5C sugar
- Double-stranded (typically)
- Contains INTRON sequences
- Remains in nucleus to facilitate storage of genetic material
RNA
- Nitrogenous bases: AUGC
- Ribose as its 5C sugar
- Single-stranded (typically)
- Does NOT contain intron sequences
- Can travel outside the nucleus – is translated on ribosomes that are bound to the ER or free-floating in the cytoplasm
