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
DNA
Replication
Preparing for mitosis
or meiosis
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13
Replication Facts
• DNA has to be copied
before a cell divides
• DNA is copied during the S
or synthesis phase of
interphase
• New cells will need identical
DNA strands
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14
DNA Replication
• Enzyme Helicase unwinds
and separates the 2 DNA
strands by breaking the
weak hydrogen bonds.
• Two strands open forming
Replication Forks (Yshaped region)
3’
5’Parental DNA Molecule Replica
3’
Fork
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15
DNA 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.
16
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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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????????