DNA Structure DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix. A molecule of DNA is made up of millions of tiny subunits called Nucleotides. Each nucleotide consists of: 1. Phosphate group 2. Pentose sugar 3. Nitrogenous base

Nucleotides Each base will only bond with one other specific base. Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Form a base pair.

DNA Structure Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

DNA Structure To crack the genetic code found in DNA we need to look at the sequence of bases. The bases are arranged in triplets called codons. A G G - C T C - A A G - T C C - T A G T C C - G A G - T T C - A G G - A T C

A gene is a section of DNA that codes for a protein. Each unique gene has a unique sequence of bases. This unique sequence of bases will code for the production of a unique protein. It is these proteins and combination of proteins that give us a unique phenotype.

Protein DNA Gene Trait

Your Task On the whiteboards and in your notes, draw a flow chart to show how to get from:

Your Task – Part Two Attempt to build the structure of DNA using a set of rules and our prior knowledge (from these notes!) on DNA 10 minutes to create a model of DNA on “DNA Molecule 1” 3 partners will draw and share their structures on the whiteboard. Be able to defend your structure with the rules that are given

Nucleotides Phosphate Pentose Sugar Nitrogenous Base

Nucleotides The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. There are four types of nitrogenous bases.

Nucleotides A Adenine T Thymine G Guanine C Cytosine

G G A T T A A C T G C A T C

DNA Replication

Genes as Information Transfer gene A gene is the sequence of nucleotides within a portion of DNA that codes for a peptide or a functional RNA genome Sum of all genes = genome

DNA Replication is Semiconservative template Each strand of the parent DNA is used as a template to make the new daughter strand DNA replication makes 2 new complete double helices each with 1 old and 1 new strand

Steps in DNA Replication 1. DNA helicase breaks the hydrogen bonds holding bases together. 2. DNA polymerase adds new complementary nucleotides to each original strand from 5’ to 3’. 3. Each new DNA molecule is identical to the parent DNA molecule and is composed of an original strand and a new strand.

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