The Molecular Basis of Inheritance

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Slide 1

Life’s Operating Instructions

In 1953, James Watson and Francis Crick shook the world

With an elegant double-helical model for the structure of deoxyribonucleic acid, or DNA

Slide 2

DNA, the substance of inheritance

Is the most celebrated molecule of our time

Hereditary information

Is encoded in the chemical language of DNA and reproduced in all the cells of your body

It is the DNA program

That directs the development of many different types of traits

Slide 3

Concept 16.1: DNA is the genetic material

Early in the 20th century

The identification of the molecules of inheritance loomed as a major challenge to biologists

Slide 4

The Search for the Genetic Material: Scientific Inquiry

The role of DNA in heredity

Was first worked out by studying bacteria and the viruses that infect them

Slide 5

Evidence That DNA Can Transform Bacteria

Frederick Griffith was studying Streptococcus pneumoniae

A bacterium that causes pneumonia in mammals

He worked with two strains of the bacterium

A pathogenic strain and a nonpathogenic strain

Slide 6

Griffith found that when he mixed heat-killed remains of the pathogenic strain

With living cells of the nonpathogenic strain, some of these living cells became pathogenic

Slide 7

Griffith called the phenomenon transformation

Now defined as a change in genotype and phenotype due to the assimilation of external DNA by a cell

Slide 8

Evidence That Viral DNA Can Program Cells

Additional evidence for DNA as the genetic material

Came from studies of a virus that infects bacteria

Slide 9

Viruses that infect bacteria, bacteriophages

Are widely used as tools by researchers in molecular genetics

Slide 10

Alfred Hershey and Martha Chase

Performed experiments showing that DNA is the genetic material of a phage known as T2

Slide 11

The Hershey and Chase experiment

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