1910s Timeline - John Innes Centre

1930s L F La Cour develops
new cytological techniques
In 1929 Len La Cour publishes
his first paper on ‘New fixatives
for plant cytology’ in Nature.
This is followed up in 1931 by
‘Improvements in everyday
technique in plant cytology’ in
the Journal of the Microscopical
Society. These modestly titled
contributions mark the start of
La Cour’s career as a pioneer in
the development of techniques
for studying the chromosomes
of plants (and animals). By this
time he has become highly
skilled in the preparation of
chromosomes from a wide
variety of difficult material from
ferns to flowering plants and
insects. At the age of 24 he is
acknowledged as the expert in
this field and he mentors all
students who come to JIHI to
see chromosomes. His
experiments yield important
improvements in pre-treatment,
fixation, embedding and
staining of material. Before his
work methods, all using light
microscopy, were only just
satisfactory for ‘easy’ species
with low numbers of large
chromosomes. Even simple
chromosome counts were
fraught with problems, and each
species and tissue required
different treatments. La Cour’s
techniques helped reveal the
inner structure and coiling of the
chromosomes, and Darlington’s
contributions to cytological
theory were based on his
preparations. La Cour has
worked his way up from his first
job as a lab-boy, whose tasks at
Merton included cleaning
windows.
See also:
Dan Lewis, ‘Leonard Francis La
Cour 1907-1984’, Biographical
Memoirs of Fellows of the Royal
Society, 32 (1986): 357-375
1931 Geneticists in USA
provide cytological proof of
crossing-over
Harriet B. Creighton and
Barbara McClintock, at Cornell
University, Ithaca, New York,
demonstrate cytological proof
of crossing-over in maize. Their
work shows that genetic
recombination is caused by a
physical exchange of
chromosomal pieces.
Darlington had laid the
foundations of this idea in his
work on meiosis in 1929-30. In
contrast to ‘classical’ cytological
theory, which favoured a system
that retained the integrity of the
chromosome, Darlington’s
theory required breakage and
rejoining of chromatids as the
cause of crossing-over and the
exchange of genetic
information.
See:
C. D. Darlington, ‘A cytological
demonstration of ‘genetic’
crossing-over (Hyacinthus)’,
Proc. Royal Society of London, B,
107 (1930): 50-59.
Dan Lewis, ‘Cyril Dean
Darlington 1903-1981’,
Biographical Memoirs of Fellows
of the Royal Sociey, 29 (1983):
113-157, esp. pp. 131-32.
1931 JIHI affiliates to the
University of London for postgraduate
research and higher
degrees
The liberal policies of the
University of London allow
workers at affiliated research
institutes to register for higher
degrees without any formal or
informal contact with a college
or school of the University. This
arrangement remains until
1960.
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