DNA contains the genetic instructions used in the development and functioning of all known living organisms. It is found in the nuclei of cells and organelles called mitochondria. DNA is made up of nucleotides containing combinations of four bases that code for the production of proteins. Genes are sections of DNA that carry these instructions. Through DNA replication, cell division, and sexual reproduction, organisms pass their genetic material to offspring. Mutations in genes can result in genetic variations that impact traits.

1. How
DNA
Works

2. • DNA is found in
the cells of all
organisms, from
mosquitoes to
bacteria to humans
• Each organism has
a unique set of
DNA, but DNA
functions the same
way in all
organisms.

3. Unraveling DNA
• 1) DNA is often wound around proteins,
coiled into strands, and then bundled up
even more
• 2) In a cell that lacks a nucleus, each
strand of DNA forms a loose loop within
the cell
• 3) In a cell with a nucleus, the strands of
DNA and proteins: are bundled into
chromosomes

4. See the Difference!

5. • 4) The order of the bases on one side of
the molecule is a code that carries
information.
• 5) A gene consists of: a string of
nucleotides that gives cell information

7. Genes and Proteins
1) DNA code reads like a book—from 1
end to the other, in 1 direction
2) Bases form the alphabet of the code.
Groups of 3 bases are the codes for
specific amino acids.
3) Example: 3 bases CCA form proline.
4) A long string of amino acids forms a
protein. Thus, each gene is usually a: set
of instructions for making a protein.

8. Proteins and Traits
1) Proteins are found throughout cells
and cause: most differences you
see.
2) Proteins act as chemical triggers
and messengers.
3) A single organism may have
thousands of genes that code for
thousands of proteins.

9. Help From RNA
1) RNA: ribonucleic acid,
a molecule that is
present in all living
cells and plays role in
protein productions
2) RNA is so similar to DNA
that is can serve as:
temporary copy of a
DNA segment

10. Making of a
Protein (Figure 2):

12. Changes in Genes
1) Mutation: Changes
in the number, type,
or order of bases on
a piece of DNA
1) Deletion: base is
left out
2) Insertion: extra
base added
3) Substitution:
wrong base is
used

13. Do Mutations Matter?
• Three possible consequences to
changes in DNA:
1) An improved trait
2) No change
3) Harmful trait
• When error is found, it is usually fixed
• If the mutation occurs in the sex cells, the
changed gene can be passed from one
generation to the next.

14. How Do Mutations Happen?
1) Mutations happen regularly because of:
random errors when DNA is copied
2) Also, damage to DNA can be caused by
abnormal things that happen to cells
3) Any physical or chemical agent that can
cause a mutation in DNA is called a
mutagen.
4) Examples of mutagens: X-rays, UV
radiation, cigarette smoke

15. Uses of Genetic
Knowledge
• Genetic Engineering
1) Genetic engineering:
when scientists
manipulate individual
genes within an
organism
2) New products created: Genetically
engineered
drugs, food, fabrics peanut plant
3) For example, bacteria may
be used to make the
proteins found in a
spider’s silk

16. • Genetic
Identification
1) Your DNA is
unique, so it can
be used like a
fingerprint to
identify you.
2) DNA fingerprinting
identifies: the
unique patterns
in an individual’s
DNA

17. 1) Identical twins
have truly identical
DNA. Scientists
are now able to
create something
like a twin, called a
clone. A clone is a
new organism that
has an exact copy
of another
organism’s genes.