DNA

• Genetic material is located in nucleus• The genetic information is stored in

Deoxyribonucleic acid, DNA • Genetic information is copied from DNA and converted

to protein

The Nucleus

• Most cells only have 1 nucleus.• How ever a few cells have more than nuclei

making them multinucleated.• This only occurs in cells that have a large

volume and there fore a large mass.• One type of cell (Red Blood Cells) do not

have a nucleus making them anucleated.

Nucleus

• The nucleus is bound by a membrane called the nuclear envelope.

• It’s a double layer membrane with fluid in between.

• At certain points the layers fuse and nuclear pores form.

• These pores are large and allow many molecules as well as mRNA to easily pass through.

Nucleus

• Inside of the nucleus there are the chromatin (pre-condensed Chromosomes) and a couple of nucleoli.

• The nucleoli are where ribosmomes are made.

Nucleus

• Chromatins are made up of DNA and histone proteins.

• Histone proteins are simply globular proteins that help DNA to keep it’s shape and be supported.

DNA (Deoxyribo Nucleic Acid)

DNA is two long chains of Nucleotides•A Nucleotide consists of:

•A phosphate Group•A five carbon sugar (deoxyribose)•A Nitrogenous Base

DNA

• The sides of the DNA strand are the connection of the Phosphates to the Sugars.

• Each Phosphate is connected to deoxyribose by a covalent bond.

DNA

• There are four nitrogen bases that make up the “rungs” of the ladder

• Adenine • Guanine• Cytosine• Thymine

Four bases...Each of the four bases has a specific shape.

Purine bases• Adenine and

Guanine• Two carbon rings

Pyrimidine bases• Thymine and

Cytosine• A single carbon

ring

A two carbon ring can only attach to a single carbon ring.

DNA• Each base pair is

held together by a hydrogen bond.

• Adenine only pairs with Thymine and Cytosine only pairs with Guanine.

• They are called complimentary base pairs.

DNA Molecules

• Two polynucleotide chains are joined

• Double helix, twisted in right handed way

• Full circle in every 10 bases

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DNA DNA ReplicatioReplicatio

nnPreparing for Preparing for

mitosis or meiosismitosis or meiosis

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Replication FactsReplication Facts• DNA has to be copied DNA has to be copied

before a cell dividesbefore a cell divides• DNA is copied during DNA is copied during

the the SS or synthesis phase or synthesis phase of of interphaseinterphase

• New cells will need New cells will need identical identical DNA strandsDNA strands

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DNA ReplicationDNA Replication• Enzyme Enzyme HelicaseHelicase

unwinds and separates unwinds and separates the 2 DNA strands by the 2 DNA strands by breaking the breaking the weak weak hydrogen bonds.hydrogen bonds.

• Two strands open Two strands open forming forming Replication Replication Forks (Y-shaped region)Forks (Y-shaped region)

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ReplicationReplicationForkFork

Parental DNA MoleculeParental DNA Molecule

3’

5’3’

5’

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DNA ReplicationDNA Replication• An enzyme called DNA

polymerase grabs new nucleotides found floating in the cell and adds the new complimentary nucleotides to the single DNA Strand.

DNA Replication

• As the new nucleotides are attached Covalent bonds form between the sugar of one nucleotide and the phosphate of the other nucleotide.

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DNA Replication

• In each new DNA strand one side of the double helix is the original molecule and the other side is the new strand.

• This is called Semi-Conservative replication.

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Stages of Mitosis

• What are they????????