Name
Date
Teacher
Assessment type: Investigation – text alternative
Task: The significance of meiosis
An important feature of meiosis is the variation that is introduced as homologous
chromosomes pair up along the equator before the first division of the cytoplasm.
For this task assume the original (parent) cell contains three pairs of homologous
chromosomes.
The first division of meiosis
Work through the sections and answer the questions.
How do the maternal and paternal chromosomes separate from one another during
meiosis?
There are two alternative hypotheses which can be proposed to answer this question.
Hypothesis 1: After pairing of the homologous chromosomes, all the maternal
chromosomes go to one daughter cell and all the paternal chromosomes go to the other
daughter cell.
Hypothesis 2: After pairing of the homologous chromosomes, the maternal chromosomes
and the paternal chromosomes separate more or less at random. Some maternal and
some paternal chromosomes go into one daughter cell and the remainder into the other.
1.
How many different combinations of maternal and paternal chromosomes will there
be in the gametes if all the maternal chromosomes were to move to one end of the
spindle and all the paternal chromosomes to the other? Explain.
If you were to arrange the chromosomes according to the second hypothesis, you
would separate the maternal and paternal chromosomes at random, with some
maternal and some paternal chromosomes going into one cell and the remainder into
the other.
2.
Would it be possible to get all the maternal chromosomes to one side of the equator
and all the paternal chromosomes to the other by chance?
3.
If so, how often would you expect this to happen (in terms of probability)?
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Separation of the chromosome pairs

At this point in meiosis the paired chromosomes move apart towards opposite poles of
the spindle.

Each daughter cell will contain three pairs of chromatids still attached at the
centromere.
This completes the first division of meiosis.
The second division: Separation of the chromatids
The second division of meiosis involves the separation of the chromatids into four haploid
gametes.
4.
How many chromosomes did the original cell contain?
How many chromosomes did each of the gametes contain?
How many gametes result from the meiotic division of the original cell?
Are gametes haploid or diploid?
5.
Write down the combinations of the characteristics (ABC, AbC etc) which occurred in
the gametes produced.
6.
Could repeating meiosis give any different combinations of characteristics?
If so, what are they? You may choose to work this out mathematically.
Studying the data
Now consider what happens as a result of random separation of maternal and paternal
chromosomes.
7.
How many different kinds of gametes (with respect to the combinations of
characteristics they carry) were produced?
8.
How many possible kinds of gametes could one get from a parent with two
alternative forms for each of the three characteristics on the chromatids (parent
AaBbCc)?
9.
In practice, matings almost always produce offspring with different combinations of
the three pairs of characteristics involved. Which is more likely to be taking place:
separation of maternal and paternal sets or random separation of the chromosome
pairs? Explain.
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10. If you were to work through the stages of meiosis and its significance in variation by
modelling the chromosome sets, briefly comment on the limitations of experimental
design when using models to represent real-life events.
11. The members of a litter of puppies or a litter of kittens produced by mating usually
produce several different coat colours.
Use your knowledge of meiosis and random fusion of gametes to explain the
presence of several different coat colours amongst each of these litters?
12. Use an example of an Australian organism to demonstrate the significance of
variation in the gene pool of a population in a changing environment.
List the sources of variation in the gene pool.
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