Interest Grabber A Family Tree Section 14-1 A Family Tree To understand how traits are passed on from generation to generation, a pedigree, or a diagram that shows the relationships within a family, is used. In a pedigree, a circle represents a female, and a square represents a male. A filled-in circle or square shows that the individual has the trait being studied. The horizontal line that connects a circle and a square represents a marriage. The vertical line(s) and brackets below that line show the child(ren) of that couple. Go to Section:

Interest Grabber continued Section 14-1 1. This pedigree shows the inheritance of attached ear lobes. Which parent has attached ear lobes? 2. How many children do the parents have? Which child has attached ear lobes? 3. Which child is married? Does this child’s spouse have attached ear lobes? Do any of this child’s children have attached ear lobes? Go to Section:

Section Outline 14–1 Human Heredity A. Human Chromosomes B. Human Traits C. Human Genes 1. Blood Group Genes 2. Recessive Alleles 3. Dominant Alleles 4. Codominant Alleles D. From Gene to Molecule 1. Cystic Fibrosis 2. Sickle Cell Disease 3. Dominant or Recessive? Go to Section:

Figure 14-3 A Pedigree Section 14-1 Go to Section: A circle represents a female. A square represents a male. A horizontal line connecting a male and female represents a marriage. A vertical line and a bracket connect the parents to their children. A half-shaded circle or square indicates that a person is a carrier of the trait. A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait. A completely shaded circle or square indicates that a person expresses the trait. Go to Section:

Figure 14-4 Blood Groups Section 14-1 Go to Section: Safe Transfusions Phenotype (Blood Type Antigen on Red Blood Cell Genotype To From Go to Section:

Interest Grabber Gender Benders Section 14-2 Gender Benders You may remember that in humans, the sperm cells may carry an X chromosome or a Y chromosome, while egg cells have only X chromosomes. Sometimes, errors during meiosis in one of the parents produce offspring with an abnormal number of sex chromosomes. Go to Section:

Interest Grabber continued Section 14-2 1. On a sheet of paper, construct a Punnett square for the following cross: XX x XY. Fill in the Punnett square. What does the Punnett square represent? According to the Punnett square, what percentage of the offspring from this genetic cross will be males? What percentage will be females? 2. On a sheet of paper, construct a Punnett square for the following cross: XXX x XY. Fill in the Punnett square. How is this Punnett square different from the first one you constructed? What might have caused this difference? 3. How do the offspring in the two Punnett squares differ? Go to Section:

Section Outline 14–2 Human Chromosomes A. Human Genes and Chromosomes B. Sex-Linked Genes 1. Colorblindness 2. Hemophilia 3. Duchenne Muscular Dystrophy C. X-Chromosome Inactivation D. Chromosomal Disorders 1. Down Syndrome 2. Sex Chromosome Disorders Go to Section:

Homologous chromosomes fail to separate Nondisjunction Section 14-2 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Go to Section:

Homologous chromosomes fail to separate Nondisjunction Section 14-2 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Go to Section:

Homologous chromosomes fail to separate Nondisjunction Section 14-2 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Go to Section:

Figure 14-13 Colorblindness Section 14-2 Father (normal vision) Normal vision Colorblind Male Female Daughter (normal vision) Son (normal vision) Mother (carrier) Daughter (carrier) Son (colorblind) Go to Section:

Figure 14-13 Colorblindness Section 14-2 Father (normal vision) Normal vision Colorblind Male Female Daughter (normal vision) Son (normal vision) Mother (carrier) Daughter (carrier) Son (colorblind) Go to Section:

Interest Grabber Bioethics and You Section 14-3 Bioethics and You As you become more aware of scientific advances in genetics, you might realize that with the ability to manipulate genes, there comes responsibility. This ability provides an opportunity to improve the lives of many people. But there is also a potential for errors or intentional misuse of the technology. Go to Section:

Interest Grabber continued Section 14-3 Working with a partner, answer the following questions. 1. In what type of situation do you think genetic engineering—changing the genes of organisms—is warranted? Explain your reasoning about your position. If you do not think that genetic engineering is ever warranted, explain your reasons for your position. 2. In what type of situation do you think genetic engineering might be misused? Suggest limits that might be placed on the manipulation of genes to avoid its misuse. Go to Section: