DNA. Genetic material is located in nucleus The genetic information is stored in Deoxyribonucleic...

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

13

DNA DNA ReplicatioReplicatio

nnPreparing for Preparing for

mitosis or meiosismitosis or meiosis

copyright cmassengale

14

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

copyright cmassengale

15

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)

copyright cmassengale

ReplicationReplicationForkFork

Parental DNA MoleculeParental DNA Molecule

3’

5’3’

5’

16

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.

copyright cmassengale 17

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.

18

Stages of Mitosis

• What are they????????