Title: Meiosis - the division leading to the creation of gametes

Author: Joanna Borgensztajn

Target group

3rd‑grade students of middle school.

Core curriculum

General requirements

I. Knowledge of biological diversity and basic biological phenomena and processes. Student:

2. explains biological phenomena and processes occurring in selected organisms and in the environment.

Specific requirements

V. Genetics. Student:

4. shows the biological significance of mitosis and meiosis, distinguishes between haploid and diploid cells.

Lesson aim

Students discuss the process leading to the creation of gametes.

Criteria for success

• discuss the course of the division of the meiotic cell;

• you will explain why gametes differ in genetic origin due to meiosis;

• you'll explain why haploid cells are not subject to meiotic divisions.

Key competences

• communicating in the mother tongue;

• communicating in a foreign language;

• Mathematical competence and basic competences in science and technology; 

• digital competence;

• learning to learn;

• Social and civic competences.

Methods/forms of work:

Mini‑lecture, didactic discussion, subject exercises.

Individual work and group work.

Teaching measures:

• abstract;

• interactive whiteboard or traditional blackboard;

• tablets/computers;

Lesson phases

Introduction

1. The teacher determines the purpose of the lesson and informs the students about its planned course. Presents the criteria for success.

2. The teacher gives the topic of the lesson, the students write it in their notebooks.

3. The teacher asks one of the students to recall information about haploid and diploid cells, autosomes and sex chromosomes.

Realization

1. The teacher explains that meiosis is a division that leads to the generation of reproductive cells: gametes in humans and animals, and spores in plants.

2. The teacher presents an ilustration entitled „Meiosis stages” and discusses the meiosis process.

3. The teacher asks the students why the meiosis process does not occur in the case of haploid individuals and individuals with an odd number of chromosomes in the cell. Students discuss their ideas and write them on the board. The teacher presents a video explaining why a plant in which somatic cells contain 3n chromosomes does not produce seeds. Next, the teacher explains that the mechanisms regulating the course of meiosis interrupt it in the case where it is not possible to match the pairs of homologous chromosomes. In this case, the body is sterile. Haploid organisms, such as bees drones, for example, produce gametes in the process of mitosis.

4. Students independently perform „Exercise 1” and complete an interactive exercises to solidify the knowledge learned during the lesson.

Summary

Students ask questions, ask for additional explanations and complete their notes.

Homework

Explain where the homologous chromosomes come from, and give how many pairs of these chromosomes occur in humans.

Learn more about meiosis using the website www.yourgenome.org, entering the phrase „facts / what‑is‑meiosis”

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Meiosis - the division leading to the formation of gametes

Meiosis is the division, which leads to the creation of four daughter cells from one original cell. Each of them contains only half of the genetic material (1n) original cell (2n). As a result of meiosis, reproductive cells (gametes) arise in humans and other animals.

During meiosis, homologous chromosomes are coming together, forming a group of 4 chromatids. Two of them in their composition have genetic material from the father, two from the mother. Chromatids twist around each other. This process can cause cracking chromatids. Such cracks are repaired immediately, but sometimes chromatid fragments are exchanged between homologous chromosomes. Next, the homologous chromosome pairs are placed in the middle of the cell, and the protein fibers pull off the individual chromosomes (made of two chromatids) in opposite directions. This division follows another, similar to mitosis.

Meiosis occurs less frequently than mitosis and is characteristic only for eukaryotic organisms. Diploid cells go through it. It is not possible in haploid cells.

The gametes produced by one and the same individual differ in their genetic material because:

• the chromosomes from the father and mother divide into gametes at random;

• during meiosis between homologous chromosomes of the same pair there is a process of random exchange of chromatid fragments, i.e. genetic recombination.

During fertilization, as a result of combining the sperm and the egg cell, a unique set of genes is created. Therefore, the children of the same parents differ in many features.

• Chromosomes consist of DNA strands and enable precise division of genetic material between daughter cells.

• Diploid cells contain a double set of chromosomes, and haploid cells - a single one.

• Prior to cell division, there is always a doubling of the amount of DNA in the cell nucleus.

• Meiosis is the division of the nucleus, thanks to which four haploid daughter cells are formed from one diploid original cell.

• Meiosis leads to the generation of reproductive cells (gametes).

• During meiosis there is a genetic recombination process, thanks to which the daughter cells are not identical