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Chapter 14
DNA: The Genetic
Material
BIOLOGY
Thirteenth Edition
Raven, Johnson, Mason, Losos,
Duncan
© 2023 McGraw Hill, LLC. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC.
, What are genes made of?
Scientists knew chromosomes were primarily made of
protein and DNA, but did not know which actually made up
genes
• DNA composed of four nucleotides while proteins
contained 20 distinct amino acids, suggesting proteins had
greater capacity for storing information
A series of experiments in 1920’s to 1950’s determined DNA
is the genetic material
© McGraw Hill, LLC 2
, Frederick Griffith – 1928
Studied Streptococcus pneumoniae, a pathogenic bacterium
causing pneumonia
Two strains of Streptococcus
• S strain is virulent
• R strain is nonvirulent
Griffith infected mice with both strains hoping to understand
the difference between the strains
© McGraw Hill, LLC 3
, Griffith’s Results 1
Injection of:
• Live virulent (S)
strain cells killed the
mice
• Live nonvirulent (R)
strain cells did not
kill the mice
Access the text alternative for slide images.
© McGraw Hill, LLC 4
Chapter 14
DNA: The Genetic
Material
BIOLOGY
Thirteenth Edition
Raven, Johnson, Mason, Losos,
Duncan
© 2023 McGraw Hill, LLC. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC.
, What are genes made of?
Scientists knew chromosomes were primarily made of
protein and DNA, but did not know which actually made up
genes
• DNA composed of four nucleotides while proteins
contained 20 distinct amino acids, suggesting proteins had
greater capacity for storing information
A series of experiments in 1920’s to 1950’s determined DNA
is the genetic material
© McGraw Hill, LLC 2
, Frederick Griffith – 1928
Studied Streptococcus pneumoniae, a pathogenic bacterium
causing pneumonia
Two strains of Streptococcus
• S strain is virulent
• R strain is nonvirulent
Griffith infected mice with both strains hoping to understand
the difference between the strains
© McGraw Hill, LLC 3
, Griffith’s Results 1
Injection of:
• Live virulent (S)
strain cells killed the
mice
• Live nonvirulent (R)
strain cells did not
kill the mice
Access the text alternative for slide images.
© McGraw Hill, LLC 4
