DNA – What Is It?
Write down everything you know
about DNA on the back of the
notetaking worksheet
What is it?
D
= Deoxyribo
 N = nucleic
 A = Acid
 Deoxyribonucleic Acid
Length of Cell Cycle:
Length of cell cycle depends on the type of
cell.
 Liver cell takes 22 hours to divide, some
cells, like nerve cells, stay in interphase for
years.
(liver cell)

DNA Replication

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Ensures that each
daughter cell has
genetic information to
carry out its activities.
DNA carries all the
cells instructions.
DNA is passed from
parent cell to
daughter cells.
Structure of DNA




DNA molecule looks like a
twisted ladder
The molecule is known as
a “double helix”
Sides of molecule are
made of sugar
(deoxyribose) and
phosphate
Rung of molecule is made
of nitrogen base pairs
DNA Structure Continued


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Rung of molecule is
made of nitrogen
bases
Names of bases:
(A) adenine
(T) thymine
(G) guanine
(C) cytosine
DNA Structure Continued


One unit made up of a
phosphate, sugar and
nitrogen base is called
a Nucleotide.
Nucleotide = base +
sugar + phosphate
Replication Process

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Replication starts by the
molecule unwinding and
separating.
They separate between the
nitrogen pairs (on the rungs)
Free floating nitrogen bases
pair up with bases on each
half of the DNA molecule.
A always pairs with T
G always pairs with C
The order will exactly
match the parent DNA
molecule
Answer the following questions on a
sheet of paper.
1.
2.
3.
4.
5.
What does the length of the cell cycle
depend on?
What does DNA stand for?
Name 2 reasons DNA replication is so
important.
Describe what a DNA molecule looks like.
What is another name for a DNA molecule?
6. What are the sides of the DNA molecule
composed of?
7. What are the “rungs” of the DNA molecule
composed of?
8. What are the names of the “rungs” of a DNA
molecule?
9. What is a nucleotide and what are they
made of?
10. Draw a picture of a DNA molecule and label
each part.
11. List the steps of DNA replication.
12. Describe which base pairs always pair up
together during replication.