Topic: Pea inheritance, environment and phenotype

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. Student:

6 ) presents single‑gene inheritance, using the basic concepts of genetics (phenotype, genotype, gene, allele, homozygote, heterozygote, domination, recessiveness).

General aim of education

Pupils describe the results of Mendel's experience.

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;

• explain what determines, for example, the height of the human body and the height of the pea shoot.

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.

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 initiates a conversation introducing the topic.

  • What do you know about ...?

  • Have you ever met ...?

Realization

• Participants familiarize themselves with the content presented in the interactive illustration. Then the teacher discusses the issues with the students.

• Students, working alone or in pairs, perform tasks indicated by the teacher.

• The teacher gives examples of traits influenced by the environment (eg increase in people, height of pea plants) and examples of features that the environment has no influence on (eg eye color in humans, flower color or leaf shape in plants).

• 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

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

• Make at home a note from the lesson using the sketchnoting method.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Pea inheritance, environment and phenotype

Genetic cross illustrates how genes are passed on from parents and what genotypes are created in a descendant generation. The genetic cross includes symbolically stored genotypes (in relation to the analyzed genes) of the parental generation and all possible genotypes of the generation of descendant.

How to explain the result of Mendel's experiment using a genetic cross? The tall pea has two dominant alleles responsible for tall growth (DD) and is the dominant homozygote, short pea is a recessive homozygote and has two alleles responsible for short growth (dd). After the intersection of the parental generation (tall pea x short pea), all plants in the descendant generation were heterozygotes of tall growth (Dd). Each of these plants inherited one gene after the tall ancestor and one gene after the short ancestor. The dominant allel combined with recessive pair (Dd) means that the recessive allel is not implemented and has no effect on plant height. Thus, in the first descendant generation, all plants are heterozygous with long stems.

When the pea flowers from the first generation (Dd) are pollinated among themselves, we will receive a second generation of descendants. 3/4 of the plant of this generation has a tall growth, and 1/4 – a short growth. If we analyze the genotypes of individual plants of the second generation, it will turn out that 1/4 are dominant homozygotes, 2/4 (half), heterozygotes, and 1/4 are recessive homozygotes. The ratio of individual genotypes: Dd:Dd: dd is therefore 1: 2: 1, respectively.

In a similar way as the height of the shoot, the color of the pea flowers is inherited.

The environment can affect the phenotype. One of these phenotype traits is body height. If the pea on the DD or Dd genotype grew in the wrong environment, it would not reach its maximum height. In peas, height is conditioned by one pair of genes and the influence of the environment.

In man, body height is conditioned by many genes and the living environment. Tall parents generally have tall children. At present, because the children's living conditions are better than their parents, the descendants are growing more than their parents. However, if during development the children of tall parents lacked enough nutrients, they would not reach the genetically programmed body height.

Organisms with the same genotypes may look different if they are inhabiting different environments. If two identical grafts from one plant are planted in different soils, and the pots are set in places with different light access, after some time, although they are genetically identical, they will differ.

• A genotype is a set of genes of a given individual, and the phenotype is a set of its features.

• Genes and the environment affect the phenotype.

• In the case of crossing the dominant and recessive homozygote, we obtain heterozygotes which have phenotypic features such as the dominant homozygote.

• In the case of crossing two heterozygotes, offspring are formed with a 1: 2: 1 ratio of genotypes whose phenotypes have a ratio of 3: 1.