Lesson Notes By Weeks and Term v4 - SHS 1
THE HUMAN BODY AND HEALTH
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THE HUMAN BODY AND HEALTH
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Subject: General Science
Class: SHS 1
Term: 2nd Term
Week: 18
Grade code: 3.4.1.LI.2
Strand code: 4
Sub-strand code: 1
Content standard code: 3.4.1.CS.1
Indicator code: 3.4.1.LI.2
Theme: RELATIONSHIPS WITH THE ENVIRONMENT
Subtheme: THE HUMAN BODY AND HEALTH
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This lesson explores the fascinating and critical topic of hereditary diseases. Heredity is why we resemble our parents – we inherit traits like our height, skin colour, and hair type. However, sometimes, faulty genetic information can also be passed down, leading to diseases. In Ghana, conditions like sickle cell anaemia affect many families, making this topic deeply relevant. Understanding how these diseases are inherited is the first step towards managing them, making informed family planning decisions, and reducing the social stigma often associated with them.
Starter Activity: Think-Pair-Share (10 mins) Think (2 mins): "Look at the person sitting next to you. What are two things you can observe that make you different from them (e.g., height, eye colour, shape of nose)? Where do you think these features come from?" Pair (4 mins): Discuss your thoughts with your partner. Do you share any similar traits with your parents or siblings? Share (4 mins): The teacher invites a few pairs to share their ideas with the class. This leads into the concept of heredity.
Part 1: The Basics of Heredity Heredity: This is the passing on of physical or mental characteristics (traits) from parents to their children (offspring) through their genes. Traits: These are specific characteristics of an individual. Examples: Physical Traits: Skin colour, height, hair type (e.g., curly or straight), eye colour, tongue-rolling ability. Hereditary Diseases: These are also traits, but they are harmful variations that cause illness. Genes and Alleles: Think of your body's instruction manual as a set of books called chromosomes. You get one set from your mother and one set from your father. Each "sentence" in these books is a gene. A gene is a segment of DNA that codes for a specific trait. For example, there's a gene for haemoglobin (the protein in red blood cells). Alleles are the different versions of the same gene. For the haemoglobin gene, there is an allele for normal haemoglobin (let's call it A) and an allele for sickle-cell haemoglobin (let's call it S). Dominant vs. Recessive Alleles: A dominant allele shows its effect even if the individual only has one copy of it. A recessive allele only shows its effect if the individual has two copies of it. In the case of sickle cell, the normal allele (A) is dominant over the sickle cell allele (S). Genotype and Phenotype: Genotype: The genetic makeup of an individual (the combination of alleles, e.g., AA, AS, SS). Phenotype: The observable physical characteristic resulting from the genotype (e.g., having normal blood cells, being a carrier, or having sickle cell disease). Part 2: Exploring Specific Hereditary Diseases
A. Sickle Cell Anaemia
This is a very important disease to understand in Ghana and across West Africa. Cause: It is caused by inheriting two copies of the recessive sickle cell allele (S). The genotype is SS. This causes the red blood cells, which are normally round and flexible, to become hard, sticky, and shaped like a crescent moon or "sickle". Inheritance: A person with genotype AA has normal haemoglobin. A person with genotype AS has the "sickle cell trait". They are carriers but are generally healthy. They have one normal allele and one sickle allele. A person with genotype SS has sickle cell anaemia. Example (using a Punnett Square): Let's see the possible outcomes if two carriers (AS) have a child.