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.

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?

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?

Concept Map Section 14-1 Autosomol Disorders caused by Recessive alleles Dominant alleles Codominant alleles include include include Albinism Galactosemia Tay-Sachs disease Huntington’s disease Sickle cell disease Cystic fibrosis Phenylketonuria Achondroplasia Hypercholes- terolemia

Figure 14-3 A Pedigree Section 14-1 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.

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

Figure 14-8 The Cause of Cystic Fibrosis Section 14-1 Chromosome # 7 CFTR gene The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein. Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane. The cells in the person’s airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus.

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.

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?

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

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

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

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

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)

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)

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.

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.

Section Outline 14–3 Human Molecular Genetics A. Human DNA Analysis 1. Testing for Alleles 2. DNA Fingerprinting B. The Human Genome Project 1. Rapid Sequencing 2. Searching for Genes 3. A Breakthrough for Everyone C. Gene Therapy D. Ethical Issues in Human Genetics

Locating Genes Section 14-3 Gene Sequence Promoter Start signal Gene Stop signal

Figure 14-18 DNA Fingerprinting Section 14-3 Restriction enzyme Chromosomes contain large amounts of DNA called repeats that do not code for proteins. This DNA varies from person to person. Here, one sample has 12 repeats between genes A and B, while the second sample has 9 repeats. Restriction enzymes are used to cut the DNA into fragments containing genes and repeats. Note that the repeat fragments from these two samples are of different lengths. The DNA fragments are separated according to size using gel electrophoresis. The fragments containing repeats are then labeled using radioactive probes. This produces a series of bands—the DNA fingerprint.

Figure 14-21 Gene Therapy Section 14-3 Bone marrow cell Normal hemoglobin gene Nucleus Chromosomes Bone marrow Genetically engineered virus

Click a hyperlink to choose a video. Human Sex Determination Videos Click a hyperlink to choose a video. Human Sex Determination Nondisjunction Point Mutation Video Contents

Click the image to play the video segment. Human Sex Determination Click the image to play the video segment. Video 1

Click the image to play the video segment. Nondisjunction Click the image to play the video segment. Video 2

Click the image to play the video segment. Point Mutations Click the image to play the video segment. Video 3

Go Online Links from the authors on DNA samples Career links on geneticists More information on the Human Genome Project Interactive test For links on pedigrees, go to www.SciLinks.org and enter the Web Code as follows: cbn-4141. Internet

Interest Grabber Answers 1. This pedigree shows the inheritance of attached ear lobes. Which parent has attached ear lobes? The father 2. How many children do the parents have? Which child has attached ear lobes? Three; the daughter 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? The second son; no; yes, the daughter Section 1 Answers

Interest Grabber Answers 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? One half of the offspring will be males; the other half, 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? One of the gametes has two X chromosomes instead of just one. This might have resulted from a mistake in meiosis: Instead of separating, the pair of X chromosomes stayed together. 3. How do the offspring in the two Punnett squares differ? Instead of two XX and two XY offspring, there are one XX and one XY (which are normal), plus one XXX and one XXY (which are abnormal). Section 2 Answers

Interest Grabber Answers 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. Students’ answers likely will include medicinal uses of genetic engineering, such as gene therapy for genetic diseases and production of needed substances such as insulin. Some students may object to all genetic manipulations. 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. Students’ answers may include the “designing” of human babies with desirable traits and the cloning of humans. Some students may object to genetically altered foods. Section 3 Answers

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