Week 3 299-306
Meiosis
3 and 4
Where it all came from and where genes are shuffled
Note: Meiosis mentioned below is referred to meiosis in sexual reproduction unless specified.
Outcomes:
Identify and explain:
 What diploid and haploid are;
 How many chromosomes there are in an egg/ a sperm/ zygote;
 All terminologies under this Big Idea (as listed in the glossary);
 What meiosis is;
 The changing of number of chromosomes and formation of new combination of alleles;
 The significance of meiosis;
 How ‘shuffling’ works in meiosis;
 The differences between sexual reproduction and asexual reproduction; and
 The stages of meiosis.
To be able to:
 Appreciate the importance of understanding meiosis and its role in genetic inheritance in sexual
reproduction.
Content:
Lesson 3
What is meiosis?
 Meiosis is the process that produces gametes with half the number of chromosomes seen in
somatic cells.
 Gametes have half the diploid number (i.e. haploid).
 It is after fertilisation, when the egg nucleus and the sperm nucleus fuse (thus the creation of a
zygote), the diploid number of chromosomes is restored.
o 23 + 23 = 46
o n + n = 2n, where n=23
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The production of an egg (ovum) is called oogenesis
The production of a person is called spermatogenesis
The changing of number of chromosomes and formation of new combination of alleles
 Meiosis halves the chromosome number, reducing it from diploid to haploid. This means each
gamete contains just one member of each homologous pair of chromosomes.
 Meiosis produces random combinations of the members of the different homologous
chromosome pairs. This means in a large number of gametes, any member of one homologous
pair can be found with any member of the other homologous pairs.
 Meiosis splices parts of the one chromosome with its partner homologue. This means gametes
contain chromosomes with new genetic combinations differing from those in the precursor cells.
The significance of meiosis – why is it so important?
 The key purpose of meiosis is that it produces variability among the offspring produced by sexual
reproduction.
 No two offspring are the same (this is not to be confused with identical twins), thus creating
diversity in a population.
How does shuffling work? The recombination produces variation
 Gametes carry unique genetic combinations because of crossing over between homologous
chromosomes and because of independent disjunction of chromosomes during meiosis.
 This re-assortment of genetic material to produce new genetic combinations is known as
recombination and is a major cause of variation in offspring of the same parents.
So how is sexual reproduction different to asexual reproduction?
 Asexual reproduction means one parent organism gives rise to offspring through the process of
meiosis, producing offspring that are genetically identical with each other and with the parent
organism.
Stages of meiosis
 Prophase 1
 Metaphase 1
 Anaphase 1
 Telophase 1
 Prophase 2
 Anaphase 2
 Telophase 2
Activities:
Lesson 4
There are 4 different types of activities a teacher may wish employ in allowing students to illustrate
their understanding of meiosis. The activities below have different emphasis on various intelligences. A
teacher may wish to adopt an activity most suited to the classroom dynamic he/ she is teaching.
Activity 1:
Use of Slowmation (Slow Animation)
 The aim of the task is for students to use modelling clay to illustrate their understanding of each
stage (and how each stage connects to other stages) of meiosis.
 The advantage of this particular task is that the presentation is a ‘flowing’ animation without
breaks.
 This task also allows students to exercise their ICT skills.
 Slowmation website: http://www.slowmation.com/
Should the task be too time-consuming, a teacher may wish to omit the animation section of the
activity and instruct the students to simply show frame by frame on a poster/ board.
Activity 2:
Traditional cut-and-paste activity to illustrate the process of meiosis.
 This involves separating diagrams of each stage from the explanations (see above diagram).
 The aim of the task is to match the correct explanation to each diagram, as well as putting each
stage in order.
 This task can be done in combination of an oral presentation.
Activity 3
An interpretative dance
 This involves putting students into groups of 8, each representing a strand belonging to a
chromosome.
 The aim of the task is allowing students to illustrate their understanding of meiosis through an
interpretive dance during the stages of meiosis.
 This task is best done with a narrative, thus allowing a teacher to understand the students’
interpretation of meiosis.
Activity 4
Meiosis song
 This task involves students to work in groups of 4 to create a song that illustrates their
understanding of meiosis and the stages involved.
 This type of task can be adapted to suit any topic.