MODELLING MEIOSIS AND FERTILISATION IN THE
MAGLOOP
“Magloops” are much simpler organisms than human beings.
For a start, they do not have 23 pairs of chromosomes, they
have only 1 pair. Magloop biology, however, is the same as
human biology. In other words, they undergo meiosis and
fertilisation just like us!!
The task for your group of three is to model the process of
meiosis and fertilisation and to predict the genotypes of the
Magloop offspring produced.
Materials needed:
Butcher’s paper
Pipecleaners of various colours
Textas
PART A: MEIOSIS IN THE FEMALE MAGLOOP
On your butcher’s paper your group needs to draw a cell and attach one pair of pipecleaner
chromosomes.
You are going to model the process of meiosis and establish which alleles will end up in the
gametes of this Magloop female organism. Because chromosomes exist in pairs, there are
two alleles for every gene; one on each chromosome of the homologous pair. You can stick
your pipecleaners onto the butcher’s paper then label the alleles on each chromosome. Label
one allele “A” and the other allele “a”. Use the butcher’s paper and textas to draw in the cell
membrane etc. Draw and use pipecleaners to model each stage in meiosis until you end up
with 4 daughter cells. Remember that the DNA in each chromosome replicates before cell
division so that the doubled chromosome consists of two identical chromatids.
Part A Discussion Questions
1. How many chromosomes did the original Magloop parent cell have?
2. Where would this parent cell be found in this female Magloop? (Assume Magloops have
similar internal anatomy to humans!)
3. What do you notice about how many chromosomes the gametes have? Why is it so
important that the gametes contain this number of chromosomes?
4. Alleles are variations of the one gene. For example, if the gene was for “skin colour”
then the alleles might be “purple skin” and “green skin”. In your Magloop organism, the
gene you have marked has two different alleles (A and a) and is said to be “heterozygous”
for that gene. Would the sister chromatids (the two chromatids of the same
chromosome) have the same or different alleles? Explain.
5. Your Magloop’s genotype is Aa. It is “heterozygous” for that gene. What do you think it
means for an organism to be “homozygous”? Give an example of a homozygous
genotype and draw a diploid cell of a Magloop that is homozygous for the A gene.
6. When you modelled Meiosis, what alleles were found in each gamete (daughter cell), with
respect to the A gene?
7. What would the gametes be that the female Magloop is producing by meiosis?
8. What is the chance/probability of a gamete containing an “A” allele? An “a” allele?
PART B: MEIOSIS IN THE MALE MAGLOOP
The Magloop in Part A was a female. You now need to model meiosis in the male Magloop.
The process is the same, but this time the type of gametes produced will be different. Since
you have been through this process fully in Part A, you can simply construct the four
expected gametes with their pipecleaner chromosomes and labelled alleles.
Part B Discussion Questions
9. What cells would be undergoing meiosis in the male Magloop?
10. What would the gametes be that are being produced?
PART C: MODELLING FERTILISATION
You now need to redraw the four female and four male gametes side-by-side on the same
sheet of butcher’s paper. This next step might take a bit of space! It is time to model the
process of fertilisation.
In the process of fertilisation, one egg cell randomly meets one sperm cell. These cells fuse
together and the resulting “zygote” has the normal number of chromosomes.
EGG
SPERM
CELL
+
contains
1 chromosome
contains
1 chromosome
ZYGOTE
Contains 1 pair of chromosomes
How many possible ways can one egg combine with one sperm? You need to show on your
butcher’s paper ALL the zygotes it is possible to form.
Each zygote will eventually form a new Magloop due to mitosis. All cells in the Magloop will
contain the genotype (combination of alleles) of the zygote.
Write down the genotypes for each new Magloop offspring it is possible to form.
Part C Discussion Questions
11. How many different genotypes are possible in the offspring from these two Magloops?
What are these genotypes? (Write down the allelic combinations).
12. If a second fertilisation was to happen, what genotypes do you think it would be possible
to produce in the offspring? Explain.
13. In humans, how many chromosomes are found in the gametes? Are they paired or
unpaired chromosomes? Explain the importance of the gametes having this number of
chromosomes. In your explanation, demonstrate your understanding of meiosis and use
the term “homologous chromosome”.
14. How many alleles are possible for an individual to possess for each gene? Explain fully.
Conclusion
Summarise the key points you have learnt about the process of meiosis including the
outcomes (end products) of meiosis and of what importance this process is in sexual
reproduction.
This is an assessed practical and must be written up as a formal practical report.