Subject: DNA and chromosomes

Target Group

A student of the 8th grade of elementary 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:

1. presents the structure and role of DNA,

3. describes the structure of the chromosome (chromatids, centromere) and gives the number of chromosomes in human cells and distinguishes between autosomes and sex chromosomes.

The purpose of the lesson

Students explain how the genetic information is stored in the cell.

Criteria for success

• explain how the DNA strand is built and where it is stored in the cell;

• you describe the structure of the chromosome;

• you will explain how many chromosomes are in human cells;

• provide examples of organisms that have a different number of chromosomes than humans.

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competences and basic scientific and technical competences;

• IT competences;

• the ability to learn;

• social and civic competences.

Methods / forms of work

Miniplication, presentation, work with film, brainstorming, didactic discussion, subject exercises.

Individual work and collective work.

Teaching aids

• abstract;

• Tablets / computers;

• interactive or traditional whiteboard.

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 the notebooks.

Realization

1. The lecturer using the illustrations available in the resources of the Internet, presents the methods of storage of genetic material by eukaryotic, prokaryotic and virus cells. Then it focuses on eukaryotes: it discusses the structure of DNA strand and the structure and function of chromosomes.

2. The teacher informs students that a certain amount of DNA is stored in the mitochondria and chloroplasts, but they do not form chromosomes. He explains that the egg of each animal contains mitochondria, but the sperm of human and other mammals leaves all of its organelles outside the egg cell. Mammals (including humans) inherit DNA found in the mitochondria exclusively from the mother.

3. The lecturer asks the mentees why the DNA thread is twisted. Students report their ideas and write them on the board. The teacher verifies the hypothesis.

4. The teacher determines the amount of chromosomes in the somatic cells of the human body and instructs students to find information on the number of chromosomes in somatic cells of other organisms. Pupils discuss the reasons for the presence of different amounts of chromosomes in different species.

5. Students perform interactive exercises to check the level of mastery of knowledge learned during the lesson.

Summary

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

Homework

Discuss the biological significance of mitosis and meiosis.

Vocabulary

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

DNA and chromosomes

In almost all organisms, genetic information – or information about their structure and functioning – is contained in DNA, deoxyribonucleic acid. In organisms with a nucleus (eukaryotic) the majority of the DNA is stored in the cell nucleus, which is a kind of control centre of the cell. A certain amount of DNA is also found in the mitochondria and chloroplasts, but chromosomes aren’t made there. Positive DNA is often inherited from one parent - in the case of people after their mothers.

Individual sections of DNA, are called genes, they contain instructions on the structure of cellular proteins and the various processes taking place in the cell. When the cell does not divide, the nucleus DNA is in loosely arranged threads, and the instructions within it can be read freely.

Before a cell divides, the amount of DNA contained in it doubles, and the threads twist strongly. During the division sticky, elongated structures are formed from them, which can only be seen under a microscope. These are chromosomes. They consist of two chromatids, that connect with each other in the place called the centromere.

The number of chromosomes in cells is specific to a given species. In people it is 46. 44 of them are called autosomes and 2 are sex chromosomes. The latter are marked with the letters X and Y. Women have somatic cells with 44 autosomes and 2 X chromosomes, and men have 44 autosomes, one X chromosome and one Y.

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

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