Unit 3:  Continuity of Life

Chapter 9: Huntington Disease

The Biology Project: Recombinant DNA Technology
Is Huntington disease always passed on from a parent to a child? Learn more about the genetics of Huntington disease by analyzing electrophoresis data. This problem set shows you a gel containing fragments of DNA from the children of a man who became ill with Huntington disease.

Chapter 10: Sex Chromosomes

The Biology Project: Sex-Linked Inheritance
Sharpen your skills in predicting the results of crosses involving sex-linked traits. This Biology Project page provides links to a variety of Mendelian genetics problems, allowing you to learn about constructing pedigrees, mapping chromosomes, sex-linked traits, genetic disorders, and much more.

Morgan: A Genetics Tutorial
Nettie Stevens was only one of the early researchers to work on sex chromosomes and sex determination. The geneticist Thomas Hunt Morgan, whose experiments are discussed several times in Chapter 10, performed many experiments on fruit flies to eventually deduce that certain traits are carried on sex chromosomes. This highly interactive, 10-page lesson reviews Morgan's experiments on sex determination and the inheritance of sex-linked traits.

Chapter 10: Transposed Genes

Barbara McClintock
Geneticist Barbara McClintock was awarded the Nobel Prize more than 30 years after completing her work on transposed genes. This Web page of the Marine Biological Laboratory—where McClintock first worked when she was earning her PhD—describes McClintock's career and the different challenges she encountered as a female scientist.

McClintock and the Ac/Ds Transposable Elements of Corn
How did McClintock actually reach the conclusion that DNA can move around in an organism? By crossing together different maize plants and then taking a careful look at the colors of different kernels in each of the offspring. Learn more about transposons with this detailed analysis of her experiments.

Chapter 11: Patents for Genes

What Are Patents Good For?
Greenpeace joins in the heated debate over gene patenting. Read about the organization's position on European legislation regarding patenting of genes and gene products.

Chapter 12: X-chromosome Inactivation

Human Karyotypes Exhibiting Various Abnormalities
What traits are caused by abnormalities in the X or Y chromosome? Identify differences among the karyotypes for people with Down syndrome, Klinefelter syndrome, and other genetic disorders.

Chapter 12: Polymerase Chain Reaction

What The Heck is PCR?
A faculty member at the University of Kansas answers this question and more—including the definition of primers, how PCR is performed, and how PCR is used to distinguish the DNA of different species.

Access Excellence About Biotech: Kary Mullis
Kary Mullis—the inventor of PCR—has been described as an intellectual maverick. He explored characteristics of matter for his PhD dissertation, and later developed the idea behind PCR while cruising a California highway.

The Biology Project: Molecular Biology
Visit this Biology Project page for links to information on recombinant DNA technology, biotechnology, and the Human Genome Project.

Polymerase Chain Reaction—Xeroxing DNA
This MIT site provides a good explanation of PCR—the process by which an identical copy of DNA can be made in less than two minutes. Further explore genetic engineering techniques with links on the use of DNA for "fingerprinting" and personal identification.