1. Chapter 28
DNA-Life’s Code

2. Objectives
• 1. Describe the structure of DNA
• 2. Explain how DNA controls genetic
traits
• 3. Describe how DNA copies itself and
works to make proteins

3. Six features of a DNA model
• 1. DNA has two main sides. They are
like rungs of a ladder.
• 2. Each side is made up of two different
chemicals: sugar and acid. They
alternate along each side
• 3. There are parts that connect the
sides together and they look like rungs
of a ladder

4. • 4. Nitrogen bases form the rungs of a
DNA molecule
• 5. There are 4 different nitrogen bases
in DNA. The letters A, T, C and G
stand for the four bases.
• 6. The four bases join in certain ways
to form the rungs. A will only fit with T
and C will only fit with G.
• Once DNA is forms it twists into a spiral
shape

5. DNA Structure
Sugar
Side parts
Acid
DNA molecule
Ladder like Nitrogen base A
Pair together
Nitrogen base T
Rung parts
Nitrogen base C
Pair together
Nitrogen base G

6. How DNA Works
• Through experiments scientists were
able to discover that DNA controls traits
• The order of nitrogen bases forms a
DNA code
• If the order of the bases are even
slightly different, then the trait is very
different

7. • DNA directs the making of proteins in cells in
the ribosome's of the cell
• The DNA is in the nucleus, but the proteins
are made in the ribosome's, which is located
in the cytoplasm
• A helper protein, RNA, carries the DNA from
the nucleus to the ribosome.
• The genetic code translates the DNA code
into protein code so that certain traits can be
duplicated

8. How DNA Copies Itself
• When DNA is ready to make a copy of
itself the following steps happen:
2. The molecule begins to open up along
its middle. Like a zipper opening up
3. Loose nitrogen bases of sugar and
acid begin to pair up with the opened
rungs.

9. • A joins to T and C joins to G
• As they join the genetic code is written
and the rungs join together
• They are exact duplicates of the cell,
so the new cell has the same genetic
code as he other cell
• Insert video