Topic: Human sex determination, sex inheritance

Target group

8th‑grade students of elementary school

Core curriculum

General requirements

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

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

Specific requirements

V. Genetics. Pupil:

7. depicts human sex inheritance.

General aim of education

Students discuss the method of human sex determination.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• distinguish between sex chromosomes and autosomes;

• explain, using the symbols X and Y, the way inheritance of sex in man;

• explain why some features are sex‑linked.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• exposing

  • exposition.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Before classes

• Students get acquainted with the content of the abstract. They prepare to work on the lesson in such a way to be able to summarize the material read in their own words and solve the tasks themselves.

Introduction

• The teacher gives the topic, the goals of the lesson in a language understandable for the student, and the criteria of success.

• The teacher asks students to briefly explain the differences between the X and Y chromosome. He asks students what they know about gender inheritance..

Realization

• The teacher introduces the concept of karyotype and discusses the differences between the karyotype of the woman and the karyotype of the man. As a curiosity, it also provides information on the methods of gender determination deviating from the one found in mammals (eg birds, insects).

• The teacher presents the students with an illustration of sex chromosomes, and then discusses the distinguish between the X chromosome and the Y chromosome in terms of the traits conditioned by the genes found on these chromosomes.

• Students carry out the interactive exercises checking the level of knowledge learned during the lesson. The teacher initiates a discussion during which the correct solutions for all the exercises performed by the students are discussed.

Summary

• The teacher briefly presents the most important issues discussed in class. He answers the additional questions of the proteges and explains all their doubts. Students complete notes.

Homework

• Imagine that you have the opportunity to interview an academic - a specialist in the field of today's lesson. What questions would you like to ask him? Write them down.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Human sex determination, sex inheritance

The set of chromosomes present in human somatic cells is called karyotype. The human karyotype consists of 22 pairs of autosomes and one pair of sex chromosomes. The sex chromosomes, called X and Y, differ in their structure and the presence of different genes.

In addition to autosomes A (44 chromosomes = 22 pairs), women have two X chromosomes in their somatic cells, therefore their karyotype is recorded as 44AXX, and men – in addition to autosomes, have one X chromosome and one Y, which means that their karyotype is 44AXY.

There are few genes in the Y chromosome, mainly conditioning the formation of male sex characteristics. In the X chromosome present in the karyotype of both sexes there are genes conditioning the development of female sexual features (until it is revealed which two X chromosomes are needed) and nearly 1200 other genes, significant for the health of both women and men. These include genes responsible for correct colour perception, blood coagulation, muscle function.

The genetic sex of a human is shaped at the time of fertilization. It depends on the sex chromosome that is contained in the sperm that fertilizes the egg cell. Sperms have either the X chromosome or the Y chromosome. In the egg cell there is an X chromosome. If the egg cell is fertilized with the sperm with the Y chromosome, the 44AXY karyotype will be created, i.e. a boy will be born. If the sperm containing the X chromosome penetrates the egg cell, a 44AXX karyotype will be created and a girl will be born. The theoretical probability of a given child's birth is 50%.

• The human karyotype consists of 46 chromosomes: 44 autosomes and two sex chromosomes.

• Human sex is determined by the presence of sex chromosomes: in women - two X chromosomes, in men - one X chromosome and one Y chromosome.