Understand how a gene is a stretch of DNA on a chromosome. Find out about alleles in their role as versions sequence variants of a gene. [8:18]

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

Learn about the gene as a stretch of DNA on a chromosome. Also find out about alleles as versions or sequence variants of a gene. [8:17]

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

This video segment from the Secret of Life School Video: "Genetic Medicine: Tinkering with Our Genes" explores the potential for gene therapy to cure diseases like Alzheimer's.

The homeobox genes that define the basic body plan of mice and fruit flies are illustrated in this graphic from The Human Evolution Coloring Book by Adrienne Zihlman. The accompanying article describes how these genes act as "molecular architects" in all animal species.

In this animation, a molecular menagerie of small molecules is displayed, with two particular molecules singled out for attention: rapamycin and furrowstatin. [1:57]

Follow human geneticist Spencer Wells, Director of the Genographic Project of the National Geographic Society, as he tracks down the genetic changes associated with the ability to digest lactose as adults, tracing the origin of the trait to less than 10,000 years ago, a time when some human populations started domesticating animals. [14:52]

Biology 2e is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes various types of practice and homework questions that help students understand—and apply—key concepts. The 2nd edition has been revised to incorporate clearer, more current, and more dynamic explanations, while maintaining the same organization as the first edition. Art and illustrations have been substantially improved, and the textbook features additional assessments and related resources.

By the end of this section, you will be able to do the following:

List the steps in eukaryotic transcription
Discuss the role of RNA polymerases in transcription
Compare and contrast the three RNA polymerases
Explain the significance of transcription factors

By the end of this section, you will be able to do the following:

List the different steps in prokaryotic transcription
Discuss the role of promoters in prokaryotic transcription
Describe how and when transcription is terminated

By the end of this section, you will be able to do the following:

Describe the different steps in RNA processing
Understand the significance of exons, introns, and splicing for mRNAs
Explain how tRNAs and rRNAs are processed

By the end of this section, you will be able to do the following:

Describe the different steps in protein synthesis
Discuss the role of ribosomes in protein synthesis

By the end of this section, you will be able to do the following:

Explain the “central dogma” of DNA-protein synthesis
Describe the genetic code and how the nucleotide sequence prescribes the amino acid and the protein sequence

Biology is designed for multi-semester biology courses for science majors. It is grounded on an evolutionary basis and includes exciting features that highlight careers in the biological sciences and everyday applications of the concepts at hand. To meet the needs of today’s instructors and students, some content has been strategically condensed while maintaining the overall scope and coverage of traditional texts for this course. Instructors can customize the book, adapting it to the approach that works best in their classroom. Biology also includes an innovative art program that incorporates critical thinking and clicker questions to help students understand—and apply—key concepts.

This comprehensive study guide covers the main terms and concepts needed for a unit on human chromosomes and genes.

A free CK-12 account is required to view all materials.

This explanation of genetic drift is straightforward and easy to understand. Illustrations are provided to help visual learners

This animated lesson will explain how genes are inherited in pairs, one from the mother and one from the father.

At DNA from the Beginning, choose from classical genetics, molecules of genetics, genetic organization and control. Each concept is explained through animation, an image gallery, video interviews, biographies and links.