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Chapter 9: DNA: The Molecule of Heredity Links

Understanding the structure and replication of chromosomes is an important goal in modern biological research. Abnormalities in chromosome structure can also be important in diagnosis and treatment of diseases such as cancer. These sites present the genetic and physical maps of human chromosomes, provide exercises for examining DNA structure, and introduce you to some of the researchers who are actively involved in this research.

Cytogenetics Gallery

Actual pictures of the structures of normal and defective human chromosomes are shown, and great hyperlinked definitions of terms such as chromosome are given.

Karyotyping Activity

Practice being a clinical cytogeneticist—a person who analyzes human chromosomes. This kind of activity is used to interpret results from amniocentesis.

The Human Genome

The known locations and functions of many human genes are summarized at this site (as of 1999). Click on a chromosome and then on a region to see what genes have been mapped to that position on the chromosome. You’ll find that we do not yet know the functions of many of the genes that have been mapped!

Chromosome 19

This site is from the Lawrence Livermore National Laboratory Human Genome Project. You can see the genes mapped to chromosome 19. Click on them to get their DNA sequences!

Chromosome Web Sites

Links are available here that take you to sites around the world that are involved in mapping and sequencing the human genome. You can get specific information about a particular chromosome.

2) What Is the Structure of DNA?

James D. Watson

The biography of one of the "discoverers" of DNA structure is presented at this site, which also includes really great pictures—even some from when Watson was just a kid.

Rosalind Franklin

Rosalind Franlkin's biography is summarized here. Her experiments provided the data that Watson and Crick used to solve the structure of DNA.

DNA Structure Activity

You will need to follow the directions and download a (free) demo version of a program called PCMolecule if you use a PC or MacMolecule if you use a Mac. Then you can examine the structure of DNA in great detail. Follow the quiz to see if you can figure out where the sugars, the phosphates, and the bases are in the three-dimensional model. This is really fun!

3) How Does DNA Replication Ensure Genetic Constancy?

Werner Syndrome and Progeria

This site, in Scientific American’s "Ask the Experts" series, reports statements from scientists involved in research in the area of premature aging syndromes.

Human Genetic Mutations

Although relatively complicated, this site contains a database of all of the known mutations in human genes. You can search for any condition you are interested in (Werner syndrome, hemophilia, cystic fibrosis, etc.) and see the actual DNA changes that have been found in people with these diseases.

Cystic Fibrosis Mutations

This interesting site shows the known mutations that lead to cystic fibrosis and also presents the frequency with which the 24 most common mutations (alleles) are found in various populations.

Chemical Safety

Are you curious about the hazards of a particular chemical? You can use the links here to find out if the chemical is known to cause mutations or is associated with other hazards.