You can tell people apart by their fingerprints because everyone’s are a

little bit different…

DNA is like a fingerprint because everyone’s is a little different!

Every living thing has DNA. That means that you have something in common with

a zebra, a tree, a mushroom and a beetle!!!!

DNA stands for:D: DeoxyriboseN: NucleicA: Acid

DNA is too small to see, but under a microscope it looks like a twisted up ladder!

DNA is packed tightly in the cell

Learning Target: Describe the structure of a

DNA molecule

chromosome

histones

DNA doublehelix

Supercoils

DNA is made up of steps and rails like a ladder.

This is a rail/side

This is a step/rung

Green can only go with Red

Purple can only go with Yellow

H bonds

Nucleotide

Sugar-phosphate backbone

DNA Structure:

organic polymer made up of repeating nucleotides

A

T

C

G

Nitrogen Bases

Building blocks of DNA: Nucleotides

The sugar = Deoxyribose

The phosphate The phosphate

Shape = pentose

The nitrogenous bases

Purines

The nitrogenous bases

Pyrimidines

How are the pyrimidines different from the purines?

Purines =(2 Carbon rings) Pyrimidines = (1 Carbon ring)

A G C T

Four different NucleotidesBASIC

STRUCTURE

DNA is a polymer formed by base pairing: Base pairing rule

PRACTICE BASE PAIRING

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A G T C C G T T A G T

T C A G G C A A T C A

The Double HelixA.The overall shape of DNA is described as a

double helix (a twisted ladder).B.What forces holds the two strands together?

Covalent BondsHydrogen bonds

Who Discovered the DNA Structure?

• Watson and Crick – 1953• Model was a rope ladder

that had been given a twist = double helix

http://www.immediart.com/catalog/images/big_images/SPL_E_H400040-Watson_and_Crick_with_their_DNA_model-SPL.jpg

Where have we seen DNA being replicated?

Cell cycle MITOSIS AND MEIOSIS

DNA Replication• 1. DNA “unzips”

– Enzymes (helicases) break H bonds b/w nitrogen bases– Forming a replication fork (where the 2 strands

separate)

• 2. Free DNA nucleotides pair up along the nitrogen bases – DNA polymerases (enzymes) make sure that the bases

pair correctly

• 3. Bonds form– Covalent bonds form b/w sugars and phosphates – Hydrogen bonds form b/w nitrogen bases for both

molecules

DNA Replication• Result: 2 new exact copies of original

DNA molecule/ happens b/4 mitosis

• See page 316 in book and animations

DNA Replication

• ANIMATION

• ANIMATION DETAILED

How are DNA and RNA similar?

• DNA is composed of nucleotides and RNA is composed of nucleotides

How are DNA and RNA different?

How are DNA and RNA different?

• DNA…– Nucleotides = deoxyribose sugar– Double helix structure– Stays inside nucleus

• RNA…– Nuleotides = ribose sugar– Single-strand structure– Located both inside and outside of nucleus– Uracil instead of thymine (U instead of T)

Enzymes involved in DNA replication

• Helicase – opens the double helix to allow for replication

• DNA polymerase – reads the original DNA strand and lays down complementary bases

• Ligase - glues the newly formed DNA together

DNA replication practice

• You are DNA polymerase. Helicase has opened the DNA strand – read each side and produce the complementary copies.

__________________________________A G G T A A C C G G T T A C G A T T A TT C C A T T G G C C A A T G C T A A T A

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

PRACTICE BASE PAIRING RULES AGAIN

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A G T C C G T T A G T

T C A G G C A A T C A

Protein Synthesis= transcription and translation

• DNA contains all the information for your traits – the genes

• These genes are blueprints and need to remain safe – kept inside the nucleus

• Copies can be made though – a messenger