DNA Structure

Double Helix

Two molecules that are arranged into a ladder-like structure that DNA consists of.

Nucleotide

Millions of tiny subunits that make up a molecule of DNA.

Nucleotide contents

• Phosphate group

• Pentose sugar

• Nitrogenous base

Phosphate and sugar

Form the backbone if the DNA molecule.

Nitrogenous bases

Form the ‘rungs’ of the DNA molecule. There are 4 types.

Adenine and Thymine

• Double hydrogen bonds

• Form a base pair

Cytosine and Guanine

• Triple hydrogen bonds

• Form a base pair

Complementary base pairing

• Each base will only bond with one other specific base.

• Therefore, the order of the bases in one strand determines the order of the bases in the other strand.

Codons

Triplets that the bases are arranged into (we need to look at the sequence of bases to crack the genetic code found in DNA).

Gene

A section of DNA that codes for a protein. They are unique.

Protein

• Coded by genes (sections of DNA)

• Unique sequences of bases code for the production of unique ___s.

• Them and their unique combinations give us a unique phenotype.

Unique sequence of bases

• Each gene has a set of these.

• Code for the production of a unique protein.

Phenotype

Proteins and combinations of proteins coded by unique sequences of bases give us a unique ___.

Histones

Eight proteins that DNA strands are wrapped around.

Nucleosomes

Formed by DNA strands wrapping around eight proteins called histones.

Chromatin

• Formed if a cell is not dividing

• Loosely coiled

Chromosome

• Formed if a cell is dividing

• Coils tighter