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Chapter 6
Genes and Gene Technology
DNA
 Deoxyribonucleic acid
 Hereditary material that controls all
the activities of a cell
 contains the information to make new
cells
 provide instructions for making
proteins
Nucleotide
 A subunit of DNA
 Consists of a sugar, a phosphate, and
one of the four nitrogenous bases
 A, C, T or G
 Nucleic acid- a biochemical that
stores information needed to build
proteins
A, T, C, G




Adnenine – pairs with Thymine
Thymine – pairs with Adenine
Cytosine – pairs with Guanine
Guanine – pairs with Cytosine
Ribosome
 A small organelle in cells where
proteins are made from amino acids
What Do Genes Look Like?
 Chromosomes are made of DNA and
proteins
 Traits (appearance)are determined by
genes (codes of DNA)
 Genes are passed from generation to
generation
 Genes are located on the
chromosomes
The gene material must
 Able to supply instructions for cell
processes and for building cell
structures
 Able to be copied each time a cell
divides
Early Studies
 Suggested that DNA was a simple
molecule and therefore thought
protein carried heredity information
 1940’s – scientists discover that
genes of bacteria are made of DNA
Chargaff’s Rules
 1950’s – Erwin Chargaff found the
amount in adenine in DNA always
matches the amount of thymine
 Also, the amount of cytosine always
matches the amount of guanine
 Clue 1 to the structure of DNA
A Picture of DNA
 Clue 2 for the shape of DNA
 Rosalind Franklin (1920-1958)
 Used x-ray diffraction (bombard the
DNA molecule with x-rays that
bounce off and create a pattern)
 Created a picture of DNA molecule
Franklin’s Picture
 Died at the age of
38 due to cancer
 Discriminated
throughout her
career by Wilkins
and Watson
Watson and Crick
 Discovered that DNA was helical in
shape (double helix)
 Franklin’s picture
 Spiral shape
 Chargaff’s rules
 Bases in pairs
 Double strand
Watson and Crick
 Won the Nobel prize in 1962 with
Maurice Wilkins
 Rosalind Franklin receive no mention
because the Nobel Prize is not
awarded posthumously
 After her death, W and C gave her
credit to their success
 Because adenine always bonds
with thymine, and cytosine
always bonds with guanine, one
side of a DNA molecule is
complementary to the other.
If the DNA segment is
 GATTACTTTAACCT
 The complementary strand would be:
 CTAATGAAATTGGA
 The complementary base pairing
allows DNA to REPLICATE or copy
itself
 DNA replicates by splitting down the
middle where the nitrogen bases meet.
 The bases on each side of the molecule
are used as a template, or pattern for
a new complementary side.
 This creates two identical molecules of
DNA.
DNA
 DNA functions the
same way for all
organisms
 DNA makes us
the same and
makes us unique
 The bases on one side of the DNA
molecule can be put in any order,
allowing an enormous variety of genes.
 Each gene consists of a string of
bases.
 The order of the bases gives the cell
information about how to make each
trait.
 The double helix
wraps around a
protein known as
a histone and
coils and
condenses until it
appears as a
chromosome
The Importance of Environment
 Remember, genes only influence your
development
 Other things affect your growth and
development
 Nutrition, exercise
Mutation?
 Is this possible?
How about this?
Mutation
 A change in the order of the bases in
an organism’s DNA
 Deletion –removing a base
 Insertion – adding a base
 Substitution – Switching bases
 Insertion
 Substitution
Mutation – Leucistic
Mutagen
 Anything that can damage or cause
changes in DNA