Lesson aims

1
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?
2
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?
3
The nature of the genetic organiser It is made of
biomolecules. 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.
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.
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.
4
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.
5
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.
6
Soon after the invention of the light microscope
in the 1700s, it was noticed that the chromosomes
of actively growing cells undergo marked changes.
7
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.
8
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.
9
In the 1920s, experiments on bacteria by Fred
Griffith showed that material from an organism
can transform other individuals of the organism.
10
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.
11
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.
12
In 1952, Briggs and King showed that the transfer
of a nucleus into an egg cell could direct its
development.
13
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.
14
In 1953, Watson and Crick suggested a structure
for DNA that suggested a mechanism for copying
and coding of information.