1. Genetics, DNA, and Heredity

2. What is DNA?
DNA - DeoxyriboNucleic Acid
Long molecule used in storing hereditary
(genetic) information makes up genes.
- “blueprints” that build an organism.

3. Gene
Gene – small piece (segment) of DNA that
codes for a specific trait.
- Trait - eye color, hair color,
height, etc.

4. Where are Genes?

5. Genes pass on hereditary material to offspring.
Asexual reproduction – all genes come from one
parent (mitosis).
- Offspring identical to parent.
Sexual reproduction – half genes from mom and
half from dad (meiosis).
- Offspring are different from parent.

6. Structure of DNA
DNA is made up of thousands of smaller
molecules called nitrogenous bases.

7. 4 Kinds of Nitrogenous Bases
a. Adenine (A)
b. Guanine (G)
c. Cytosine (C)
d. Thymine (T)
These 4 bases exist in pairs:
Guanine-Cytosine (G-C) and Adenine-Thymine (A-T)
(Good Couples are Always Together)

8. Shape of DNA
Double Helix – looks like a twisted
ladder with two strands of DNA wrapped
around each other.

9. The “Ladder” (Draw Me!)
Nitrogenous bases form
the “steps” of the ladder

10. “Packaging” DNA
The nucleus contains the
chromosomes.
Chromosomes contain
lots of DNA strands
which make up genes.

11. DNA Replication
Before a cell divides
(mitosis or meiosis) it
must replicate, or copy,
its DNA.
- This makes sure that
all cells have copies of the
DNA.

12. How is DNA Replicated?
DNA is replicated in 3 steps:
 Original DNA molecule unzips
 2 new strands begin to take form
 Two identical DNA strands are formed

13. 1. Unzip original DNA
Original DNA molecule becomes separated
(unzips).

14. 2. Expand Two New Strands
Each original strand now becomes a
template (model) for a new strand of
DNA.

15. Base pairs are added to new strand using the
same rules Good Couples Always Together.
Original New
A T
T A
T A
G C
New Strand

16. 3. Two Identical DNA Molecules are Formed
Two new DNA molecules formed, each with 1
original strand and 1 new strand.

17. Heredity and Traits
Proteins decide which
traits will be shown
by the offspring.
DNA codes for which
amino acids will
make the proteins.

18. What Organelle Makes Proteins?
The organelles that
assemble proteins
from amino acids are
the ribosomes.

19. How Does DNA’s Directions Get to
the Ribosomes?
1. A messenger molecule (RNA) copies
information from the DNA.
2. The messenger molecule (RNA) goes to
the ribosome.
3. The ribosome collects amino acids and
assembles the proteins in the proper
order.

20. Changes in Heredity- Mutations

21. Nothing is perfect…
Mutation – any changes (alterations) in the
sequence of DNA that affects genetic
information and the appearance of offspring.

22. Types of Mutations
Gene mutation – a mutation that occurs in a
single gene and affects one trait.
Ex: Eye color, Sickle cell Anemia,
Hemophilia
Chromosome mutation – a mutation that occurs
in many genes and affects many traits at once.
Ex: Down Syndrome (an extra 21st
chromosome)

23. How Can Mutations Affect an
Organism?
Body cell mutations can cause cancer.
- only the individual is affected.
Gamete cell mutations affect the egg and the sperm.
- all offspring of the individual can be affected.