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Lesson aims
We are going
to learn the
key features
of a genetic
organiser
(like DNA).
We will look
at evidence
that DNA is
the organiser.
We will
investigate
the way that
the organiser
works.
What is your definition of living?
Why do living things need a genetic
material?
Lesson aims
We are going
to learn the
key features
of a genetic
organiser
(like DNA).
We will look
at evidence
that DNA is
the organiser.
We will
investigate
the way that
the organiser
works.
What features must genetic material have?
Here are some clues!
What should it be made of?
How will it get from individual to individual
and from cell to cell?
What must it organise?
How will it improve?
How will it cope with change?
Lesson aims
The nature of the genetic organiser
We are going
to learn the
key features
of a genetic
organiser
(like DNA).
It is made of biomolecules.
We will look
at evidence
that DNA is
the organiser.
We will
investigate
the way that
the organiser
works.
It can be copied easily and mistakes are rare.
It has a direct connection with the production of
proteins.
Its instructions can be of variable length.
It must be compact enough to fit inside cells.
It must be stable but have
enough instability for
changes to happen.
Its code must have more
capacity than is needed.
It must be universal.
Observation of everyday
things gave rise to the idea of
spontaneous generation.
Muddy soil giving rise to frogs
and the action of rain on
grain to mice and rats.
The Greeks suggested the
idea of pangenesis. Pangenes
are formed in every organ.
They move through the blood
to the genitals and then to
the children. This idea results
in many of the links between
blood and heredity.
Soon after the invention of
the light microscope in the
1700s, it was noticed that the
chromosomes of actively
growing cells undergo
marked changes.
In 1869 - Friedrich Miescher
discovered a new acidic,
phosphorus containing material
in the pus on hospital blankets.
He later extracted the material
from salmon sperm cells.
He called this new substance
Nuclein.
In 1887 Edouard van Beneden reported that the
number of chromosomes was a constant for each
species
In 1902, Walter Sutton observed that chromosomes
obey Mendel's rules of inheritance.
The nucleus is rich in nuclein.
In the 1920s,
experiments on
bacteria by Fred
Griffith showed
that material
from an organism
can transform
other individuals
of the organism.
In the 1930s, Joachim Hammerling
discovered that he could alter the
characteristics of two varieties of an
alga by transplantation experiments.
The transplanted algae always reverted to the
characteristics of the part containing the
nucleus – in the base of the organism.
In 1944, Avery, MacLeod and McCarthy extracted
the transforming material discovered by Griffith
and investigated the effect of treating it with
different enzymes.
Protease, lipase and RNAase had no effect on the
transforming effect of the material.
The transforming material precipitated with alcohol
– a chemical feature of DNA.
In 1952, Briggs and King
showed that the transfer
of a nucleus into an egg
cell could direct its
development.
In 1952 Hershey and Chase
labelled the DNA and protein
coats of a type of virus that
uses bacteria to reproduce.
They allowed the viruses to
infect the bacteria but then
separated the virus coats
from the bacteria.
In 1953, Watson and Crick
suggested a structure for DNA
that suggested a mechanism
for copying and coding of
information.