The primary purpose of this activity is to help students to become aware of the existence of inherited conditions and to understand that knowing about inherited conditions can be of use in making informed decisions about personal and social issues and values. It is important that students in this stage of their development develop a positive attitude toward acquiring genetic knowledge.
A number of major inherited disorders occurs with some frequency only because there is a relatively large proportion of carriers of potentially harmful genetic traits in the general population. While having a recessive gene usually poses no health problem for a carrier, there is always the risk of serious genetic disease in any child of two carriers of the same harmful trait, or any son born to a mother carrying an X-linked defect.
Due to multiple-gene inheritance, interactions among several genes, and to an extent the activity of certain genes at a particular time in a person’s life, human heredity is very complex. Many genetic disorders are the result of mutant alleles that follow Mendelian inheritance patterns. Most of these genetic disorders can be traced to an allele for a recessive trait that codes for an ineffective or nonfunctional protein product. When the protein is an enzyme, the result in a homozygous recessive individual may be a block in an essential metabolic pathway. The lack of the product of that pathway may account for the symptoms of the disease or an excess of the precursor in the pathway may be toxic.
1. Discuss the definitions of the following terms with the class: recessive, dominant, carrier, heterozygous, homozygous, inherited disorder, mutation, genes and alleles.
Have students observe other members of the class and develop a list of obvious differences. Point out to students that these differences are referred to as ‘traits’ e.g. hair color, which are controlled by genes.
2. Divide the class into two groups.
3. Distribute the worksheets on the vocabulary discussed earlier in the lesson to one group. These students will be given instructions to match the correct meaning with each word given. (See page below).
4. Divide the remainder of the class into four groups. Distribute to each group drawings showing how each disorder is inherited. Have students figure out the odds for each offspring. Each group will work together to analyze the drawing provided. Allow each group to choose a representative who will explain to the rest of the class the way in which genetic defects may be transmitted to an individual.
5. At the end of this presentation, a representative from section A will define the terms given earlier to the rest of the class.
6. Students will be given a copy of each activity performed in class to review for homework.
Note: For Reinforcement
7. Use Polaroid slides of chromosomes and genetic conditions to be shown during the next lesson.