- describe the early experiments of Gregor Mendel and relate his conclusions to modern genetic theory
- solve monohybrid and dihybrid cross problems using Punnett squares, and use probabilities to determine the expected phenotypes and genotypes in the offspring
- explain and provide examples of dominance, incomplete dominance, and multiple alleles
- draw and follow a pedigree chart in order to track a specific allele through many generations
- describe genetic disorders that are caused or influenced by specific genes
- consider the social and ethical implications associated with genetic testing
How Are Genes Passed on from Parent to Child?
You have your mother's eyes, your father's curly hair, and your grandmother's disposition. How are characteristics passed on from one generation to the next? Why do characteristics disappear from one generation and then reappear in the next? Can you predict which characteristics will be inherited? Would you like to be able to predict the characteristics you will pass on to your children, or find out which ones have been passed on to you from your parents but have not surfaced yet?
Researchers in modern genetics laboratories now study how specific characteristics are passed on from parent to offspring. However, humans have studied the characteristics of plants and animals ever since the beginning of organized agriculture. Early farmers learned that selective breeding of the best individuals resulted in a better food supply. These early farmers did not know about DNA or genes. They practised genetic selection by choosing to breed plants and animals based on characteristics that were important to them. In selecting and breeding corn, for example, they considered the size, colour, and shape of corn kernels, as well as their nutritional content.
Today we have a better understanding of how genes are passed from parent to child. Geneticists are most interested in pinpointing the exact mechanism by which a gene is passed on to offspring, especially in the case of genetic diseases. For example, two parents who do not have cystic fibrosis, a genetic respiratory disease, may have a child who is born with cystic fibrosis. Did the cystic fibrosis gene come from both parents, or just one? Will all the children of these parents have cystic fibrosis, or just some? By understanding how genetic disease genes are passed on, geneticists are able to answer such questions. Once such questions are answered, researchers can work on treatment and prevention.
In this chapter you will investigate how characteristics are passed on from parent to child. You will find out how the rules of probability predict the offspring's characteristics. You will explore the idea of being able to determine which genes you carry, and the social and ethical consequences of finding out. Finally, you will see how certain characteristics may be valuable to one individual and detrimental to another.
STARTING POINTS
Answer the following questions using your current knowledge. You will have a chance to revisit these questions later, applying concepts and skills from the chapter.
1. How do you think genetic information gets passed on from generation to generation?
2. Why are some characteristics passed on from parent to child while others are not?
3. How might an understanding of genetic processes and the inheritance of biological characteristics benefit individuals and society?
4. Why is there so much variation in the human population with respect to what humans look like?
5. How does society benefit from the screening of harmful genes?
Mendelian Genetics - Patterns of Inheritance
KEY CONCEPTS
After completing this chapter you will be able to
- describe the early experiments of Gregor Mendel and relate his conclusions to modern genetic theory
- solve monohybrid and dihybrid cross problems using Punnett squares, and use probabilities to determine the expected phenotypes and genotypes in the offspring
- explain and provide examples of dominance, incomplete dominance, and multiple alleles
- draw and follow a pedigree chart in order to track a specific allele through many generations
- describe genetic disorders that are caused or influenced by specific genes
- consider the social and ethical implications associated with genetic testing
How Are Genes Passed on from Parent to Child?
You have your mother's eyes, your father's curly hair, and your grandmother's disposition. How are characteristics passed on from one generation to the next? Why do characteristics disappear from one generation and then reappear in the next? Can you predict which characteristics will be inherited? Would you like to be able to predict the characteristics you will pass on to your children, or find out which ones have been passed on to you from your parents but have not surfaced yet?
Researchers in modern genetics laboratories now study how specific characteristics are passed on from parent to offspring. However, humans have studied the characteristics of plants and animals ever since the beginning of organized agriculture. Early farmers learned that selective breeding of the best individuals resulted in a better food supply. These early farmers did not know about DNA or genes. They practised genetic selection by choosing to breed plants and animals based on characteristics that were important to them. In selecting and breeding corn, for example, they considered the size, colour, and shape of corn kernels, as well as their nutritional content.
Today we have a better understanding of how genes are passed from parent to child. Geneticists are most interested in pinpointing the exact mechanism by which a gene is passed on to offspring, especially in the case of genetic diseases. For example, two parents who do not have cystic fibrosis, a genetic respiratory disease, may have a child who is born with cystic fibrosis. Did the cystic fibrosis gene come from both parents, or just one? Will all the children of these parents have cystic fibrosis, or just some? By understanding how genetic disease genes are passed on, geneticists are able to answer such questions. Once such questions are answered, researchers can work on treatment and prevention.
In this chapter you will investigate how characteristics are passed on from parent to child. You will find out how the rules of probability predict the offspring's characteristics. You will explore the idea of being able to determine which genes you carry, and the social and ethical consequences of finding out. Finally, you will see how certain characteristics may be valuable to one individual and detrimental to another.
STARTING POINTS
Answer the following questions using your current knowledge. You will have a chance to revisit these questions later, applying concepts and skills from the chapter.
1. How do you think genetic information gets passed on from generation to generation?
2. Why are some characteristics passed on from parent to child while others are not?
3. How might an understanding of genetic processes and the inheritance of biological characteristics benefit individuals and society?
4. Why is there so much variation in the human population with respect to what humans look like?
5. How does society benefit from the screening of harmful genes?
Sept. 25th-28th, 2017
Note: Types of crosses
5.1 Mendelian Inheritance *do question marked with "*"
Sept 28th, 2017
5.2 Variations in Heredity *do question marked with "*"
5.3 Pedigrees *read for unit project
5.5 Genetic Disorders *read for unit project
Sept 28th, 2017
Chapter 5 Assignment, part 1: My Genetic Profile
(Due Thursday, October 5th, 2017)
Oct. 2nd, 2017
5.7 Multi-trait Inheritance *do question marked with "*"
Oct. 4th, 2017
Pedigrees (SJC powerpoint) *do questions #1-5 in 5.3
Family Pedigree Assignment (Due Wednesday, October 18th, 2017)
Chapter 5 Assignment, part 2: Dihybrid crosses (Due Wednesday, October 11th, 2017)
*UNIT PROJECT is due Oct. 18th, 2017*
Oct. 11th, 2017
Chapter 5 Self-Quiz & Review
Oct. 13th, 2017
Chapter 5 Quiz (5.1, 5.2, 5.3, 5.7)