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Paul Strode describes the HHMI BioInteractive Click and Learn activity on DNA sequencing and phylogenetic trees. He describes how it teaches students DNA sequence alignment, and how those sequence differences allow researchers to determine relationships between species. Visit www.biointeractive.org/phylo-tree to use the interactive resource, and to find related materials. Subscribe to the BioInteractive YouTube channel to get the latest educator tips!

In order to develop complex scientific explanations, students need to have many opportunities to grapple with a concept, look at it from various points of view, and analyze data representing different relationships. I plan the sequence and flow of my AP Environmental Science course strategically to ensure I am making these connections using a concept called "curriculum spiraling."

This 8-minute video is derived from the 2013 Holiday Lectures on Science. In it, Dr. Charles Sawyers explains the difference between proto-oncogenes, oncogenes, and tumor suppressor genes, and how mutations in these genes drive cancer development. "Cancer genes" can affect several cellular processes that he groups into three categories: cell growth and survival (i.e., genes involved in the cell cycle, cell fate (i.e., genes involved in cell differentiation), and genome maintenance (i.e, genes involved in DNA repair.)

Students begin by watching the online video clip and completing a worksheet. After that assignment, instructors can decide which of the two activities (or both!) to use in class. In Activity 1, students identify the locations on chromosomes of genes involved in cancer, using a set of 139 "Cancer Gene Cards" and associated posters. In Activity 2, students explore the genetic basis of cancer by examining cards that list genetic mutations found in the DNA of actual cancer patients. Small-group work spurs discussion about the genes that are mutated in different types of cancers and the cellular processes that the affected genes control. The Activity 1 and 2 Overview document provides short summaries of the two activities along with key concepts and learning objectives, background information, references and rubrics, and answers to students' questions. Both cancer discovery activities are appropriate for first-year high school biology (honors or regular), AP and IB Biology. Activity 2 is also appropriate for an undergraduate freshman biology class.

One of the most important molecules relating to cancer is called p53. This Click and Learn explains the structure and function of the p53 protein as well as how the protein's activity is regulated. Learn why p53 is called the guardian of the genome and how interfering with its function can lead to cancer.

This feature explores some of the therapies using adult stem cells, and looks at some of the experimental stem cell therapies that are going on today.

Penn State University anthropologist Dr. Nina Jablonski walks us through the evidence that the different shades of skin color among human populations arose as adaptations to the intensity of ultraviolet radiation in different parts of the world.

Meiosis, the form of cell division unique to egg and sperm production, sets the stage for sex determination by creating sperm that carry either an X or a Y sex chromosome. But what is it about the X or Y that determines sex? Before a meiotic cell divides, its two sets of chromosomes come together and cross over, or swap, segments. The first animation shows normal crossing over, where the X and Y chromosomes exchange pieces only at their tips. The second animation shows a rare mistake in which the Y chromosome transfers a gene called SRY to the X chromosome, resulting in sex-reversed babies. Studies of sex-reversed individuals led researchers to identify the master switch for sex determination, the SRY gene, which tells a fetus to become a boy.

Meiosis, the form of cell division unique to egg and sperm production, sets the stage for sex determination by creating sperm that carry either an X or a Y sex chromosome. But what is it about the X or Y that determines sex? Before a meiotic cell divides, its two sets of chromosomes come together and cross over, or swap, segments. The first animation shows normal crossing over, where the X and Y chromosomes exchange pieces only at their tips. The second animation shows a rare mistake in which the Y chromosome transfers a gene called SRY to the X chromosome, resulting in sex-reversed babies. Studies of sex-reversed individuals led researchers to identify the master switch for sex determination, the SRY gene, which tells a fetus to become a boy.

Four talks focus on sex determination-the molecular and genetic mechanisms that determine whether an organism will be male, female or a hermaphrodite.

Four talks focus on sex determination-the molecular and genetic mechanisms that determine whether an organism will be male, female or a hermaphrodite. Meisosis animation 49:00-53:00 53:21 SRY animation Y to X crossing over 53:30 SRY transfer 54:45

1:12 animation of angiogenesis

In the 2013 Holiday Lectures on Science, Charles L. Sawyers of Memorial Sloan-Kettering Cancer Center and Christopher A. Walsh of Boston Children's Hospital will reveal the breathtaking pace of discoveries into the genetic causes of various types of cancers and diseases of the nervous system, and discuss the impact of those discoveries on our understanding of normal human development and disease.

An overview of the immune system, concentrating on the roles played by B and T lymphocytes, and the antigen-presentation system.

In this classroom activity, there are chemical formulas and 3-D structural diagrams of some interesting natural and artificial molecules that students can build with a kit. To build some models, students will have to team up with one or more colleagues.

1:30 animation As a human embryo develops, its cells become progressively restricted in the types of specialized cells that they can produce. Inner cell mass (ICM) cells of the blastocyst can make any type of body cell. Gastrula-stage cells can give rise to the cells of a given germ layer. Later, cells become even more restricted. For example, the pancreatic bud of the endoderm layer can only make the cells of the pancreas.

Amanda Briody describes two BioInteractive resources focused on Gorongosa National Park in Mozambique. She uses the short film "The Guide: A Biologist in Gorongosa" to introduce students to the park and its scientists. The Gorongosa Interactive Timeline allows her to ask data-based questions on the park's history and ecology, and have students make evidence-based claims.

2:18 Human embryonic development depends on stem cells. During the course of development, cells divide, migrate, and specialize. Early in development, a group of cells called the inner cell mass (ICM) forms. These cells are able to produce all the tissues of the body. Later in development, during gastrulation, the three germ layers form, and most cells become more restricted in the types of cells that they can produce.

A data collection and analysis lesson that examines selection for coat color in pocket mouse populations on different color substrates over time.

In their study of the medium ground finches, evolutionary biologists Peter and Rosemary Grant were able to track the evolution of beak size twice in an amazingly short period of time due to two major droughts that occurred in the 1970s and 1980s. This activity simulates the food availability during these droughts and demonstrates how rapidly natural selection can act when the environment changes. Students use two different types of tools to represent different beak types to see which is best adapted to collect and "eat" seeds of different sizes. Students collect and analyze data and draw conclusions about traits that offer a selective advantage under different environmental conditions. They have the option of using an Excel spreadsheet to calculate different descriptive statistics and interpret graphs.

Vibrio harveyi is a marine bacteria that emits light only at high population density. The bacterial bioluminescence is controlled by a system called quorum sensing. In this system, signaling molecules are secreted, and when they bind to cell surface receptors, they turn on many genes, including those that produce bioluminescence.

At first glance, the research of Bonnie Bassler and Baldomero "Toto" Olivera might not appear to be medical at all. Dr. Bassler works on marine bacteria that glow in the dark, while Dr. Olivera studies venomous snails that hunt by harpooning fish. Yet their findings show what science has revealed time and again-knowledge that can be used to unlock medical secrets is often hidden in unlikely places. Nature has much to teach us, as long as we know where to look and what to look for. Join us for a four-lecture series as Bonnie and Toto guide us through intriguing slices of the natural world revealing how a deeper understanding of nature and biodiversity informs their research into new medicines.