Nucleic acids like DNA and RNA contain genetic instructions that allow cells to function. DNA, found in the nucleus, is the primary genetic material and uses base pairing between adenine, thymine, guanine and cytosine to form its double helix structure. RNA plays an important role in protein production by carrying genetic messages from DNA in the nucleus to ribosomes in the cytoplasm using base pairing between adenine, uracil, guanine and cytosine. During DNA replication, the double helix unwinds and each strand serves as a template to produce two new identical DNA molecules to be passed on to daughter cells. Genes in DNA code for specific proteins through mRNA which is translated by ribosomes.

1. I. Genetic Material
A. Nucleic Acids
-Nucleic acids contain
instructions that cells
need to carry out all the
functions of life.
Nucleic acid – very large
organic molecules made
up of carbon, oxygen,
hydrogen, nitrogen, and
phosphorus.

2. 2 Types of Nucleic Acid :
1. DNA (deoxyribonucleic acid)-
the genetic material that
carries information about an
organism. It is passed from
parent to offspring.
-DNA directs all cellular
activities and is ONLY found in
the nucleus of a cell.
2. RNA (ribonucleic acid) – a
nucleic acid found in the
nucleus and cytoplasm of
cells that plays an important
role in the production of
proteins.

3. Nucleotides & Genetic Organization
-Nucleic acids are made up of nucleotides.
Nucleotides have 3 basic parts :
1. A 5-carbon sugar.
2. A phosphate group.
3. A nitrogenous (nitrogen-containing) base.
Levels of genetic organization :
Nucleotide Gene DNA Chromosomes Genome
smallest code for made tightly coiled the entire
building our traits of many strands of DNA genetic
block of genes make-up of
a gene an organism

4. B. Composition of DNA
Major parts of a DNA nucleotide :
1. A 5-carbon sugar called deoxyribose.
2. Phosphates
3. Four different nitrogenous bases (rungs of the ladder) :
a. Adenine (A)
b. Thymine (T)
c. Guanine (G)
d. Cytosine (C)

5. Pairing the Nitrogenous Bases in DNA
*Adenine always pairs
(matches up) with thymine
and guanine always pairs
(is complementary to) with
cytosine.
-These nitrogenous bases
make up four different
possible nucleotides in
DNA.
-Many nucleotides (basic
unit of nucleic acids)
placed together make one
DNA molecule.

6. C. Structure of DNA
James Watson & Francis Crick –
American biologist & British
physicist who built the first
accurate structural model of DNA
(Nobel Prize in 1962).
-Watson & Crick’s model of DNA
was a double helix (twisted
ladder), in which 2 strands were
wound around each other.

7. Structure of DNA con’t.
-The outside/sides of the
ladder are made of
deoxyribose sugar and
phosphates.
-The rungs of the ladder
are the nitrogenous bases
(connect to deoxyribose
sugar in the outside/side
of the ladder).

8. II. DNA Replication
*Before cells divide, they
make copies of their DNA.
-DNA Replication ensures
that each daughter cell will
have all of the genetic
information it needs to carry
out its activities.
-DNA replication is
semiconservative, meaning
that when DNA copies, each
new strand has ½ of the
original strand.

9. Major steps in DNA Replication :
1. DNA unwinds (untwists) exposing the
nitrogenous bases.
2. DNA unzips – weak hydrogen bonds
between nitrogenous bases break.
*Hydrogen bonds are the weakest type
of bond that occurs in molecules.
3. New complimentary strands form –
nitrogenous bases floating in the
nucleus of the cell pair up with the bases
on each half of the DNA molecule.
4. Two new DNA molecules that are exactly
alike are formed.
-Both new strands are identical to the
original strand of DNA.

10. III. The Function of Genes in DNA
*Proteins determine the size,
shape, and many other traits
of an organism, ex : eye
color, hair color, type of
hairline, etc.
-Each gene in a DNA
molecule codes for the
production of a particular
protein.
Gene – a small portion of the
DNA molecule that codes for
a particular trait/protein.

11. Order of Nitrogenous Bases
-The order of the nitrogenous
bases along a gene forms a
genetic code that specifies what
type of protein will be produced.
-The order of the nitrogenous
bases tells the cell which amino
acids to put together to make a
protein. If one amino acid is
changed or out of place, a
different protein is made.
-Since DNA cannot leave the
nucleus to make proteins at the
ribosomes, RNA directs protein
synthesis.

12. IV. RNA (ribonucleic acid)
Major parts of an RNA nucleotide :
1. Ribose sugar (a 5-carbon sugar)
2. Phosphates
3. Four different nitrogenous bases :
a. Adenine (A)
b. Uracil (U)
c. Cytosine (C)
d. Guanine (G)

13. How RNA makes a protein
-There are 3 major types of RNA.
1. mRNA – (messenger RNA)
carries information from the
nucleus to the rest of the cell.
2. tRNA – (transfer RNA)
transfers amino acids to
ribosomes during protein
synthesis.
3. rRNA – (ribosomal RNA) makes
up a major part of ribosomes.

14. When making proteins :
1. mRNA carries DNA’s
message to the
ribosomes (site of
protein synthesis)
in the cytoplasm.
2. Ribosomes (like a
decoder ring)
translate (interpret)
the RNA code into a
protein.

15. V. Differences between DNA and RNA
1. RNA has uracil and DNA
has thymine.
2. RNA is a single helix and
DNA is a double helix.
3. RNA is very small and DNA
is very large.
4. RNA can travel between
the nucleus and the
cytoplasm, DNA is only in
the nucleus.
5. RNA has ribose sugar and
DNA has deoxyribose.