Download Genetic Peas - Southern Biological

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Genetic Peas
We supply:
Living materials
Catalogue Code: S 7.5
Culture media
Frozen materials
Background:
There is a gene controlling the colour of pea plants that has the alternate alleles:
CG
:
dark green
CY
:
yellow
Preserved materials
Skeletons
Dark green is incompletely dominant, and this is reflected in the allele symbols chosen. The
possible genotypes of pea plants and their phenotypes are as follows:
Microscopes
GENOTYPE
PHENOTYPE
G
G
Dark green
G
Y
Light green
Y
Y
Yellow
C C
Wall charts
C C
C C
Stains and Indicators
The seed provided has been obtained from plants with the genotype C GCY. Pea plants are self
fertilizing so the cross giving rise to the seeds supplied will therefore have been:
CGCY x CGCY
Seeds
Books
Genotype of seed
Chemistry Models
Anatomical Models
Earth Science
CGCG
:
2CGCY
:
CYCY
We would expect the plants obtained to approximate a 1 dark green : 2 light green : 1 yellow
ratio. Yellow pea plants have defective chlorophyll and are unable to photosynthesize.
Hence they fail to thrive and die as young seedlings.
To grow your seed:
1.
Peas should be planted in cool weather and the flowers protected from any frost.
Environmental
2.
Planting can be carried out in seed boxes filled with potting mix, or alternatively, in
well drained soil which has been lightly limed some time before the planting.
3.
Seeds should be planted at least 5 cm apart, and at a depth of 1 to 2 cm. Water
regularly until germination.
4.
The colour of the plants can be observed soon after germination, however you may
wish to allow the plants to grow, flower, self fertilize and produce seed. Generally
light green plants are not as vigorous growers as dark green plants. The yellow plants,
as mentioned above, will die as young seedlings.
Forensic Equipment
and lots more on our website
www.southernbiological.com
.
If you allow the plants to grow beyond seedlings you may need to support them on a
string trellis or similar structure.
Ref: S 7.5
1/44 Rushdale St Knoxfield 3180 or PO Box 9227 Scoresby 3179 Victoria Australia
Phone: +61 3 9753 3896 Fax: +61 3 9753 3959
Email: [email protected] Web: www.southernbiological.com
A Division of Cogitamus Pty Ltd ACN 097 468 954 ABN 25 838 926 933
20/11/01
“ a world of learning”
Genetic Peas
We supply:
Living materials
Embedded Specimens
Culture media
Microbiology
Frozen materials
Preserved materials
Skeletons & Skulls
Questions you may consider for your students (brief answers
in brackets):
Catalogue Code: S 7.5
Have the students grow the seeds without giving them the
genetic background. Observe the seedlings as they grow and
when the colour becomes obvious, hold the appropriate
discussion.
Supporting Products for
Genetic Peas:
1. How many different colours can you see in the seedlings
and what are they?
(Three different colours - dark green, light green and yellow.)
Posters:
Code; BEB 109 Germination
2. The colour variation you see in these pea plants is due to
a single gene that has two alternate alleles. What model
do you propose to account for your observations?
(There may be a variety of models proposed by the students.
In these models a variety of letters may be used to denote the
alleles. Whatever letters the students use, they should realise
that their notation must convey the appropriate genetic
relationship - in this case incomplete dominance. The allele
notation used above was really based on logic:
Anatomy models
Microscopes
Wall charts
Glass ware
Stains and Indicators
Seeds
Books
CD-ROMs
Chemistry Models
Forensic Equipment
Gel Electrophoresis
Equipment
and lots more on our
comprehensive web page.
C to relate to the trait being considered, that is, colour.
G
to relate to one of the forms, that is, dark green.
Y
to relate to the other form, that is, yellow.
The reasoning for the correct model may go something as
follows: if the gene responsible has only two alleles and yet
three phenotypes are observed, then there must be an
incomplete dominance of the dark green allele over the yellow
allele when they are together in the same plant. This results in
three different phenotypes in the offspring if each parent is
heterozygous. [You may wish to explore alternative crosses
here too in order to emphasise this point. Note that the
numbers of each plant are not critical in the reasoning here
although if large numbers are obtained a 1:2:1 would be
expected. It is the presence of the three phenotypes that is
critical.] Hence the model is a cross between heterozygous
parents. The dark green plants will be homozygous for the
dark green allele, the yellow plants will be homozygous for the
yellow allele, and the light green plants will be heterozygous
for the yellow and green alleles. The genetic notation for the
cross is the same as the cross outlined in the background
section above.
Taste Testing Equipment;
Code: G 9.70 Genetics Biokit
Seeds;
Code; S 2.1 Genetic Barley
(200 seeds)
Code; S 2.1/L Genetic Barley
(1000 seeds)
Code; S 7.1 Smooth Peas (100
seeds)
Code; S 7.2 Wrinkly Peas
(100 seeds)
Code; S 7.3 Tall Peas (100
seeds)
Code; S 7.4 Dwarf Peas (100
seeds)
Code; S 7.6 Dun Peas (2000
seeds)
Brassica Seeds;
Please see our colour
catalogue for full listings.
Books;
Code; BK 72.10 Applied
Genetics
Computer Software;
Code; 0991139HY Genetic
Engineering
Code: 0991102HY Mendel’s
Principals of Heredity
Ref: S 7.50
1/44 Rushdale St Knoxfield 3180 or PO Box 9227 Scoresby 3179 Victoria Australia
Phone: +61 3 9753 3896 Fax: +61 3 9753 3959
Email: [email protected] Web: www.southernbiological.com
21/11/01