DNA Replication Notes
Let’s clear somethings up. DNA stands for deoxyribose nucleic acid It is a double strand in the shape of a spiral called Double Helix. Both strands are held together by hydrogen bonds (weak bonds). Both strands run in opposite directions. This is called anti-parallel It is made up of nucleotides The three parts of nucleotides are Sugar Phosphate Nitrogenous Bases (Adenine, Thymine, Guanine, Cytosine) DNA holds the instructions to build different cells in our body—the same DNA is repeated in all cells. The instructions are coded in the order or sequence of nitrogenous bases.
DNA Replication Before a cell divides, the DNA strands unwind and separate Each strand makes a new partner by adding the appropriate nucleotides The result is that there are now two double-stranded DNA molecules in the nucleus So that when the cell divides each nucleus contains DNA This process is called replication
BLAST FROM THE PAST In which phase of the cell cycle does the DNA replicate? A- G1 B- S C- G2 D- M
Enzymes involved in DNA replication DNA Helicase—unzips the DNA by breaking the hydrogen bonds between the nucleotides apart. DNA Polymerase– builds a new polymer of DNA by adding nucleotides to both sides
The original strand separates when DNA Helicase breaks down the hydrogen bonds
DNA Polymerase adds nucleotides to each old strand to form two identical strands
DNA Polymerase adds nucleotides to each old strand to form two identical strands
A preview of next week… Every three nitrogenous bases codes for a protein that builds your traits! So it’s the bases that carry the genetic code! They also have the code to synthesize enzymes from organic molecules to help build and breakdown products and substrates.
What determines the traits of an organism? The order and sequence of the nitrogenous bases
Proofreading New DNA DNA polymerase initially makes about 1 in 10,000 base pairing errors. Enzymes proofread and correct these mistakes The new error rate for DNA that has been proofread is 1 in 1 Billion base pairing errors