Blueprint of Life
Topic 10: Sutton and Boveri
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
DOT POINT(s)
 outline the roles of Sutton and Boveri in identifying the
importance of chromosomes
Introduction
Towards the end of the 19th century,
cytology (the study of cells) was the
scientific area of research that was in
vogue, with many important
discoveries being made at around the
turn of the century. This is not
surprising, since compound light
microscopes had advanced to a point
where they no longer produced
distorted images, becoming the ‘new
technology’ used to reveal the
wonders of what lies within ells and to
validate evidence for new theories.
parkerlab.bio.uci.edu
Introduction
At that time, the challenge
facing biologists was to
determine what material in the
cell held the hereditary factors.
A common belief in those days
was that protein would turn out
to be hereditary material,
because protein was present in
both the cytoplasm and the
nucleus.
faculty.fmcc.suny.edu
Introduction
There was also a flurry of
activity to validate or disprove
Mendel’s findings in the late
1800s and to test whether they
could be applied to organisms
other than pea plants.
creationrevolution.com
Boveri and Sea Urchins
Theodor Boveri, a German biologist, was one of the leading
cytologists at the turn of the century. Between 1896 and 1904,
he carried out experiments on sea urchin eggs, studying the
behaviour of the cell nucleus and chromosomes during meiosis
and after fertilisation.
idw-online.de
Boveri and Sea Urchins
Sea urchin eggs were ideally
suited for study because they
could be easily fertilised in a
laboratory and have a quick (48
hour) time frame for larval
development. Boveri’s studies
were advanced for his time, as
he did not simply rely on
observations made with a
microscope, but also solved
problems by experimenting
with the larvae of sea urchins.
www.thorntonsrestaurant.com
Boveri and Sea Urchins
It was already known at the time
that each species of living organism
has a set number of chromosomes
and that, during fertilisation, an
egg cell and a sperm cell fuse.
Boveri’s experimental work with
sea urchins showed that the
nucleus of the egg and sperm each
contribute the same amount (50%)
of chromosomes to the zygote
(fertilised egg), making a
connection between chromosomes
and heredity.
www.ubqool.com
Boveri and Sea Urchins
His experiments showed:
■ when a normal egg and
sperm fused, the resulting
offspring showed
characteristics of both parents
counsellorsofwisdom.com
Boveri and Sea Urchins
His experiments also showed:
■ that if the nucleus of only one
parent was present, the larvae
resembled that parent, but showed
abnormalities. When an egg, whose
nucleus had been removed, was
fertilised with a sperm, the resulting
sea urchin larvae showed
characteristics similar to the male
parent. However, they were smaller,
had only half the normal number of
chromosomes and showed some
abnormalities.
ocean.nationalgeographic.com
Boveri and Sea Urchins
From his experiments he
deduced that:
 a complete set of
chromosomes (that is,
chromosomes in pairs) is needed
for normal development
 the inheritance ‘factors’ are
found on chromosomes within
the nucleus (chromosomes are
the carriers of heredity)
web1.beverlyhg-h.schools.nsw.edu.au
Boveri and Sea Urchins
From his ongoing studies, he realised that there are more
hereditary ‘factors’ than chromosomes and so deduced that
there must be many factors (today known as genes) on one
chromosome.
www.bbc.co.uk
Sutton and Grasshoppers
Walter Sutton (1877–1916),
an American cytologist,
studied meiosis in cells of
grasshoppers (Brachystola
magna). In contrast to the
eminent Boveri, Sutton was a
young, unknown graduate
student who produced
remarkable and detailed
drawings of his findings in
cytology.
www.kumc.edu
Sutton and Grasshoppers
As a result of his observations, he made the connection between
the behaviour of chromosomes during meiosis and Mendel’s
laws of heredity. His independent findings (1902–4), together
with those of Boveri (1902), formed the basis of the
chromosome theory of inheritance.
www.biology.iupui.edu
Sutton and Grasshoppers
Sutton’s observations of meiosis
in grasshoppers revealed that:
■ chromosomes occur in distinct
pairs, visible during meiosis in
grasshopper cells; one
chromosome of each pair is
paternal and the other maternal
(today termed homologous pairs)
and the chromosomes in each
pair have the same size and shape
pk-photography.blogspot.com
Sutton and Grasshoppers
Sutton’s observations of meiosis in grasshoppers revealed that:
■ during meiosis (reduction division), the chromosome number of
a cell is halved: the chromosomes in each pair of chromosomes
separate (just like Mendel’s factors segregate—his law of
dominance and segregation) and each gamete receives one
chromosome from each pair
■ fertilisation restores the full number of chromosomes in the
zygote.
www.tutorvista.com
Sutton and Grasshoppers
He concluded that chromosomes were the carriers of heredity
units and behaved in the same manner as Mendel’s ‘factors of
inheritance’ (genes).
www.beltina.org
Sutton and Grasshoppers
In addition, Sutton stated that:
■ Chromosomes arrange
themselves independently along
the middle of the cell just
before it divides—that is, they
assort independently of each
other during segregation, like
Mendel’s factors (evidence for
Mendel’s law of independent
assortment)
www.downsyndrome.org.za
Sutton and Grasshoppers
In addition, Sutton stated that:
■ Chromosomes are units
involved in inheritance. Sutton,
like Boveri, also believed that
several Mendelian‘factors’
must be present in one
chromosome and could
therefore be inherited as a unit.
(This is what we term ‘linkage’
today. It will be dealt with in
more detail later).
www.scienceclarified.com
Response of the scientific
community at the time
Boveri and Sutton’s chromosome
theory linking chromosomes and
heredity was regarded with
scepticism by many, but accepted
by others, causing much discussion
and debate in the early part of the
20th century. As is common in
science, Sutton and Boveri’s
deductions became hypotheses for
testing in future experiments—
scientists set about trying to
validate or disprove these findings.
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Response of the scientific
community at the time
With advances in scientific
understanding and improved
technology, their cytological
interpretation of Mendelian inheritance
was convincingly confirmed in 1915
and still holds today.
www.transtutors.com
Activity
-Handout 10.1.3 Sutton and Boveri Chart
-Students to complete Sutton and Boveri findings worksheet
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