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Overview of characteristics of various stages of cancer.

Staging describes the severity of a person's cancer based on the size and/or extent (reach) of the original (primary) tumor and whether or not cancer has spread in the body.

This page shows some key events of human development during the embryonic period of the first eight weeks (weeks 1 - 8) following fertilization. This period is also considered the organogenic period, when most organs within the embryo have begun to form. There are links to more detailed descriptions which can be viewed in a week by week format, by the Carnegie stages or integrated into a Timeline of human development. Online resources available include: individual images of all Carnegie stages, scanning electron micrographs of the earlier stages, cross-sections showing internal structures at mid- and late-embryonic, 3D reconstructions of internal structures, animations of processes, ultrasound scans and information about abnormalites of development.

The American Joint Committee on Cancer (AJCC) and the International Union for Cancer Control (UICC) maintain the TNM classification system as a tool for doctors to stage different types of cancer based on certain standards. It's reviewed every 6 to 8 years to include advances in our understanding of cancer.

This interrupted case study was inspired by and uses data from one of the largest commercial restaurant associated outbreaks of norovirus reported in the literature. It applies basic principles of epidemiology and outbreak investigation to a shellfish-linked norovirus outbreak at a Michelin star restaurant in the UK in 2009. The details of the case are taken directly from the report that was produced by the health protection agency and publications that followed. Students take on the role of an infection control team (ICT) that is responsible for identifying the extent and source of the outbreak. They are taken through different stages of the outbreak investigation and at each stage asked what their team would do in response to given pieces of information. Specifically, students uncover the scope and source of the outbreak using descriptive and basic analytical epidemiology methods. The case is suitable for first or second year introductory courses in microbiology, epidemiology, or other infectious disease related topics.

How are the stages of mitosis related to the creation of identical daughter cells? The primary function of the stages of mitosis is to make certain that each daughter cell is genetically identical to the mother cell. The mother cell's DNA is copied during interphase. During mitosis the chromosomes condense from long strands to highly coiled structures. The two copies of each DNA strand, called sister chromatids, are physically attached to one another. The chromosomes are moved to the center of the cell and split apart in a highly coordinated fashion. The condensation of the chromosomes, the physical connection of the sister chromatids, and the precise movement of the chromosomes are all important in making sure that each daughter cell has one copy of each chromosome and is genetically identical to the mother cell.

The purpose of this case is to teach introductory college biology students the basic process of mitosis, focusing on the fundamental cellular processes that occur during each of the stages-prophase, prometaphase, metaphase, anaphase, telophase and cytokinesis. It would also be appropriate for AP Biology students. The case is framed around solving a murder. The murder plot involves a naturally-occurring poison derived from Yew trees, known as paclitaxel. Paclitaxel is a mitotic inhibitor that works by inhibiting the depolymerization of microtubules so that the cell is arrested in metaphase. At the end of the case, students will be able to describe the basic process of mitosis, including the fundamental processes that occur in each stage. The discovery of paclitaxel led to the development of the chemotherapeutic drug, Taxol ®, and the case concludes by having students think about the correlations between poisons and chemotherapies. The case involves the use of videos, one of which was made by the author for this case, and can be used in a flipped classroom.

This case study was written for an introductory course for biology majors who are first learning about embryonic development. The case is composed of several parts and involves a storyline about a team of researchers who find frogs and eggs in bamboo plants during a field study. Students consider what these observations mean, learn basics about the stages of animal embryonic development, and make connections to phylogeny and natural selection. Students then apply their understanding of animal embryonic stage development to the chemical atrazine in the environment by examining data from several experiments. As a concluding activity students write a letter to an agency or newspaper of their choosing stating their opinion surrounding the use of atrazine in the environment. The case proceeds in a progressive disclosure format and involves a combination of class discussion, small group work, and homework. Because the case focuses on very basic animal embryonic development, it would also be a great start to a developmental biology course or an embryology course.

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.

1:20 Stages of Mitosis, a promotional piece, begins with a fly-through of cells preparing to undergo mitosis (cell division).

Adam Ruben's tongue-in-cheek column about the common difficulties and frustrations of reading a scientific paper broadly resonated among Science Careers readers. Many of you have come to us asking for more (and more serious) advice on how to make sense of the scientific literature, so we've asked a dozen scientists at different career stages and in a broad range of fields to tell us how they do it. Although it is clear that reading scientific papers becomes easier with experience, the stumbling blocks are real, and it is up to each scientist to identify and apply the techniques that work best for them. The responses have been edited for clarity and brevity.

This 5 lesson unit, which was designed by teachers in conjunction with scientists, ethicists, and curriculum developers, explores the scientific and ethical issues involved in stem cell research. The unit begins with an exploration of planaria as a model organism for stem cell research. Next, students identify stages in the development of human embryos and compare the types and potency of stem cells. Students learn about a variety of techniques used for obtaining stem cells and the scientific and ethical implications of those techniques. While exploring the ethics of stem cell research, students will develop an awareness of the many shades of gray that exist among positions of stakeholders in the debate. Students will be provided an opportunity to become familiar with policies and regulations for stem cell research that are currently in place in the United States, the issues regarding private and public funding, and the implications for treatment of disease and advancement of scientific knowledge. The unit culminates with students developing a position on embryonic stem cell research through the use of a Decision-Making Framework. Two culminating assessments are offered: In the individual assessment, students write a letter to the President or the President's Bioethics Committee describing their position and recommendations; In the group assessment, students develop a proposal for NIH funding to research treatment for a chosen disease using either embryonic or 'adult' stem cells.

The Visible Embryo is a visual guide through fetal development from fertilization through pregnancy to birth. As the most profound physiologic changes occur in the "first trimester" of pregnancy, these Carnegie stages are given prominence on the birth spiral.

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.

The most recent human retroviral infections leading to germ line integration took place with a subgroup of human endogenous retroviruses called HERVK(HML-2). The human genome contains ~90 copies of these viral genomes, which might have infected human ancestors as recently as 200,000 years ago. HERVs do not produce infectious virus: not only is the viral genome silenced - no mRNAs are produced - but they are littered with lethal mutations that have accumulated over time. A recent study revealed that HERVK mRNAs are produced during normal human embryogenesis. Viral RNAs were detected beginning at the 8-cell stage, through epiblast cells in preimplantation embryos, until formation of embryonic stem cells (illustrated). At this point the production of HERVK mRNA ceases. Viral capsid protein was detected in blastocysts, and electron microscopy revealed the presence of virus-like particles similar to those found in reconstructed HERVK particles. These results indicate that retroviral proteins and particles are present during human development, up until implantation.

The early stages of embryonic development shape our cells and tissues for life. It is during this time that our newly formed cells are transformed into heart, skin, nerve or other cell types. Scientists are finding that this process is largely controlled not by the genome, but by the epigenome, chemical markers on DNA that tell cells when to turn genes on and off. Now, studying zebrafish embryos, researchers at Washington University School of Medicine in St. Louis have shown that the epigenome plays a significant part in guiding development in the first 24 hours after fertilization.

2:40 video summarizing key points occurring during each stage of mitosis.

3:49 video, Alzheimer's disease is the most common cause of dementia, affecting over 40 million people worldwide. And though it was discovered over a century ago, scientists are still grappling for a cure. Ivan Seah Yu Jun describes how Alzheimer's affects the brain, shedding light on the different stages of this complicated, destructive disease.

1:38 Animated description of the digestive process and the structures of the digestive system involved at each stage.

The Rare Disease Foundation is focussed on linking basic science and clinical practice to increase the efficiency of rare disease research. This model is called Translational Care. This model drives patient based, treatment focussed research projects from disease characterization to treatment with greater efficiency. By incorporating research, astute clinician observation and parental knowledge into the various stages of rare disease research we impact the speed of discovery and the way rare conditions are managed.