Topic: The research of Gregor Mendel, genotypes and phenotypes

Author: Leokadia Stalewicz

Target group

8th‑grade students of elementary school

Core curriculum

General aim of education

Students discuss the scheme of monogenic character inheritance.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• predict the traits of offspring based on the characteristics of parents by saving a genetic cross for one trait;

• interpret a schematic record of inheritance (genetic cross) using the terms phenotype, genotype, gene, allele, homozygote, heterozygote, domination, recessiveness;

• distinguish the genotype from the phenotype.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• 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;

• packaging of F1 hybrid seeds (eg tomato, cucumber, ornamental plants).

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 reminds the participants of the classes what subject area the lesson will concern.

Realization

• Instructor, using the illustrations „Pea characteristics examined by Grzegorz Mendel” and an interactive illustration depicting the inheritance of the flower color, brings students closer to the research conducted by the aforementioned scholar. In the course of the mini‑report, the teacher explains that:

  • Mendel used in his research specially selected lines of plants (so‑called clean lines), for which he was sure that they give their offspring only a chosen feature;

  • after the crossing of two plants differing in the selected feature (eg stem length, flower color, etc.), Mendel obtained plants from the first generation (F1) exhibiting only one of these traits, which he called the dominant feature;

  • after the intersection of two hybrids from the F1 generation, Mendel received plants exhibiting the dominant trait and plants exhibiting a recessive trait in 3: 1 proportions.

• The teacher presents packages of seeds of cultivated plants (vegetables or flowers) being F1 hybrids. Then he asks students why the producers of these seeds advise against self‑propagation of the plants obtained from them. Students are looking for answers using the brainstorming method, and submit their proposals. If they fail to respond correctly, the teacher declares that the progeny plants, obtained from F1 hybrids, may not have certain features that determine their utility value.

• The teacher displays the illustration entitled „Allels” and defines this concept. Translates the difference between genotype and phenotype. He explains that for some pea traits, the heterozygote phenotype containing one dominant allele is the same as that of the dominant homozygote.

• As a curiosity, the teacher cites an example of red hair in people. The redhead person is a recessive homozygote. The recessive allele, conditioning the red hair color, is masked by the parents of such a person by the presence of an allele conditioning a different color and is not revealed in the phenotype. As a result, parents do not know that they have such copies of genes, especially if there were no redheads in their families.

• Students perform exercises and commands. The teacher checks and supplements the answers, providing students with the necessary information. Provides feedback..

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

• Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

• Write a short note about the topics covered in the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

The research of Gregor Mendel, genotypes and phenotypes

Genes of pea are responsible for the features like the height of the plant, the colour of the flowers, the colour and shape of the seeds or pods. Just like in other organisms, their features are conditioned by the genes. The collection of all the genes which forms a complete genetic information about a given organism is called the genotype. Each organism has a specific genotype. The collection of all the features of an organism, conditioned by the genotype and, to some extent, by the environment, is called the phenotype. The colour of the flowers, the shape of the seeds, the height of the stem are features of the phenotype.

As we know, in diploid cells, such as somatic cells, each chromosome exists in two copies. Genes are fragments of chromosomes, meaning that in each diploid cell there are two copies of a given gene. Those copies are called the alleles.

The alleles of a given gene can be dominant or recessive. Dominant allele is an allele which one copy in a cell is enough to generate a specific feature of an organism, called dominant feature. Recessive allele causes a given feature to appear only when in a cell there is no other allele of a given gene. Recessive alleles generate recessive features. If alleles that create pairs of genes are identical, we call such organism a homozygote from the perspective of that gene. Once an organism has two different alleles of a given gene, we call it heterozygote when it comes to that gene. Dominant alleles are marked with capital letters, whereas recessive alleles – with lowercase letters. Homozygote that has two dominant alleles of a given gene is called a dominant homozygote, whereas one that has two recessive alleles – recessive homozygote.

• Genotype is the collection of genes of a given organism, whereas a phenotype is the set of its features.

• Phenotype is influenced by the genes and the environment.

• Gregor Mendel created the basics of genetics in 19th century.