DNA

DNA Structure Monomer (basic subunit) = nucleotide Nucleotide composed of: Phosphate group 5C sugar (deoxyribose) Nitrogenous-base * 5C sugar covalently bonded to both phosphate group AND nitrogenous base

Nitrogenous bases Only FOUR bases found in all DNA structures: 1- Adenine (A) 2-Thymine (T) 3-Guanine (G) 4-Cytosine (C) Adenine forms 2 H-bonds with Thymine Guanine forms 3 H-bonds with Cytosine

Phosphate groups bond to sugars with bases attaching at right angles

Double helix structure

Chromosome structure Stop YouTube at 1:41 Strands of DNA wrap around a protein (histone) forming nucleosomes. Nucleosomes coil together forming chromatin. Chromatin loops and coils together forming supercoils. Supercoils bunch together forming chromsomes.

DNA Replication Problem: In order to duplicate (replicate) double-stranded DNA, the two strands must be separated from each other exposing nucleotide bases with complimentary base pairs being added to the “open” strand forming a new double strand. Multiple steps: UNZIP the two strands Allow matching base pair nucleotides to form new hydrogen bonds with exposed nucleotides The new double strands must be exact duplicates of the original bases and be stable

Replication enzymes Helicase used with other proteins to UNZIP double strand. DNA polymerase – primary enzyme used to add new complimentary base nucleotides to unzipped DNA at replication forks. Ligase used to close gaps and help repair incorrect sequences. Start YouTube at 1:42, go to 2:50

Click slowly on animation to see step by step process Click slowly on animation to see step by step process. Just know about DNA polymerase, not all the other enzymes.

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