DNA contains the genetic instructions that determine traits in living organisms. It is found in the form of a double helix composed of two strands of nucleotides bonded together. Each nucleotide contains a phosphate, sugar (deoxyribose), and one of four nitrogenous bases: adenine, thymine, cytosine, or guanine. The base pairing rule dictates that adenine bonds only with thymine and cytosine bonds only with guanine. DNA replicates semi-conservatively prior to cell division to produce two identical copies of the original DNA molecule. It uses messenger RNA to transport its genetic instructions to ribosomes for protein production.

1. DNA & RNA

2. The Vocabulary of DNA
 Genetics—The study of
genes & heredity
 Trait-- inherited
characteristic
determined by the
presence and
expression of dominant
and/or recessive alleles.
 Gene-- a segment of
DNA that codes for a
protein, which in turn
codes for a trait (skin

3. DNA Facts
 Chromosomes are made of DNA
 Deoxyribonucleic Acid (DNA)
 Molecule that stores genetic information in cells
 Copies itself exactly for new cells

4. DNA-Deoxyribonucleic Acid
 DNA is often called the
blueprint of life.
 In simple terms, DNA
contains the instructions for
making proteins within the
cell.

5. Proteins
 Responsible for all cell
structures and functions
 Made of long chains of
amino acids
 There are 20 amino acids in the
body
 Proteins are responsible for:
 Hair, skin, hormones, muscle
movement, antibodies, chemical
reactions, oxygenation of cells.

6. When Watson, Crick
and Wilkins got their
Nobel prize awards in
1962, Rosalind
Franklin was cheated
of deserved
recognition in part by
her early death from
cancer in 1958.
Rosalind Franklin and Maurice
Wilkins took DNA X-ray photos that
were essential to the discovery of the
double helix of DNA by James
Watson and Francis Crick in 1953.

7. Why is the Study of DNA
Important?
 It’s essential to all life on earth
 Medical Benefits—disease detection,
treatment, prevention
 Development of Crops
 Forensics

8. DNA Structure
 DNA is a polymer (composed of
repeating subunits called nucleotides)
 2 long strands
Each a chain of nucleotides

9. Nucleotides
 Consists of…
Phosphate
Carbon sugar (deoxyribose)
Nitrogen base

10. Adenine and Guanine are PURINES
 Adenine and guanine each have two rings
of carbon and nitrogen atoms.
C
C
C
C
N
N
N
Adenine N
N
C
C
C
C
C
N
N
O
N
Guanine N
N
C

11. Thymine and Cytosine are PYRIDAMINES
 Thymine and cytosine each have one ring
of carbon and nitrogen atoms.
C
C
C
C
N
N
O
N
cytosine
C
C
C
C
N
N
O
O
thymine
C

12. Types of Nitrogenous Bases
 A = adenine
 T = thymine
 C = cytosine
 G = guanine

13. DNA Strand
 Each nucleotide bonds
to the next one to form a
strand.
 The two strands twist
around a central axis to
form a double helix.
 Sides of the ladder
alternate phosphate and
sugar (deoxyribose)
 Rungs are held together
by Hydrogen bonds

14. Base Pair Rule
 Adenine can bond
only with Thymine
A-T or T-A (2 H
bonds)
 Cytosine can bond
only with Guanine
C-G or G-C (3 H
bonds)
 This is called the
BASE PAIR RULE

15. Nitrogenous Bases
 Those 4 bases
(ATCG) have endless
combinations
Just like the letters of
the alphabet can
combine to make an
infinite number of
words.
 The two strands are
said to be
complimentary
 That means that if you have
GAATAC on one side you

16. Replication
 The process by which DNA
makes a copy of itself
 Why does DNA need to copy?
 Cells divide for an organism to
grow or reproduce
 Every new cell needs a copy of
DNA
 In DNA replication enzymes
work to unwind and separate
the double helix and add
complimentary nucleotides to
the exposed strands

17. Replication
 DNA replication is semi-conservative.
 When it makes a copy, one half of the old
strand is ALWAYS kept in the new strand
 This helps reduce the number of copy errors.

18. DNA Replication
 DNA helicases—
break H-bonds
linking bases
 DNA
polymerases—
move along each of
the strands, adding
nucleotides,
according to base
pairing rules.

19. DNA Replication
 The result is two
exact copies of the
original DNA
 Each new double
helix is composed of
one original DNA
strand and one new
strand.
 Semi-conservative

20. Translation
 DNA is in the nucleus
To make proteins,
DNA must get its
instructions to the
ribosomes who make
proteins.
To transport its
instructions, it uses
Messenger RNA
(mRNA)

21. RNA
 Ribonucleic Acid
Consists only of
one strand of
nucleotides
Has ribose (a 5C
sugar) NOT
deoxyribose
Has uracil (U) as
a nitrogenous
base NOT
thymine

22. DNA by the Numbers
 Each cell has about 3
meters of DNA.
 The average human has
300 trillion cells.
 The average human has
enough DNA to go from
the earth to the sun more
than 400 times.
 DNA has a diameter of
only 0.000000002 meters.
The earth is 150 billion meters
or 93 million miles from
the sun.

23. Coming Soon