DNA: The Genetic Material• The instructions for

inherited traits are called genes

• DNA: primary material that causes recognizable, inheritable characteristics in related groups of organisms

The Shape of DNA

• A DNA molecule looks like a spiral staircase and is composed of two parallel strands of linked subunits called nucleotides

The Shape of DNA• A nucleotide has 3 parts:

phosphate group, sugar (deoxyribose), and a base

• The phosphate and sugar link together to form the back bone

• The bases pair together to connect the two strands

DNA Replication

• Step 1: Unwind and Separate the DNA Strands – Two complementary strands of DNA separate from

each other and form Y shapes called replication forks• Step 2: Add Complementary Bases – At the replication fork, new nucleotides are added to

each side according to the base-pairing rules• Step 3: Formation of Two Identical DNA

Molecules– Each double-stranded DNA helix is made of one new

strand of DNA and one original strand of DNA

Base Pairing Rules

Replication Proteins• DNA Helicase – enzyme that unwinds DNA• DNA Polymerase – enzyme that adds nucleotides to each

base to form two new double helixes; proofreads

http://www.youtube.com/watch?v=zdDkiRw1PdU

Gene Expression

• The manifestation of genes into specific traits

Two Steps: • Transcription • Translation

Transcription

• Location: nucleus

• Makes mRNA from DNA

• After mRNA is made it travels into the cytoplasm

Codon

• 3 letter code on mRNA

• Pairing rules with DNA– A – U (Uracil)– T – A– C - G

Translation• Makes protein from

mRNA in cytoplasm on a ribosome

• tRNA carries anticodons to codons which code for an amino acid

• rRNA helps to make protein

Translation

What amino acid does each codon represent?

• UUG

• GUA

• CAC

• ACU

• AGG

• CCG

= Leucine

= Valine

= Histidine

= Threonine

= Arginine

= Proline