THEFIVE

KINGDOMS

INFERTILE

HYBRIDS

A mule

A Tigron

Differences within a species

HEREDITHEREDITYY

Transmissio

n of characteristi

cs from parents to offspring

It must be able to control expression of traits

It must be able to replicate in order to be in each

cell of the organism

It must be able to change in order to ensure survival of a species in a changing

environment

CHARACTERISTICS OF HEREDITARY MATERIAL

Fred Griffith (1928) – proposed a “transforming principle” as being responsible for changing a non-pathogenic strain of bacteria into a pathogenic strain.Click here to see image

Oswald Avery (1944) – showed Griffith’s “transforming principle” to be DNA.

Alfred Hershey & Martha Chase (1952) – confirmed Avery’s result using T2 bacteriophage. Click here to see image

THE SEARCH FOR THE AGENT OF

HEREDITY

GENE

Unit of inheritance

Discrete section of DNA

Carries information for specific proteins

GENE EXPRESSIONGENE EXPRESSION The process of

transferring information encoded in a gene into its functional product

• Erwin Chargaff (1950) – A and T in equal amounts, likewise G and C, in all organisms.

• Rosalind Franklin & Maurice Wilkins (1951) – produced an X-ray diffraction picture of DNA suggesting a helical structure.

• James Watson & Francis Crick (1953) – definitive 3-D structure of DNA.

• Matthew Meselson & Franklin Stahl (1958) – showed DNA replication to be semi-conservative.

• Marshall Nirenberg & Gobind Kharana (1966) – cracked the genetic code.

A STRUCTURE FOR DNA

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