2: Cells and Mitosis
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- 2.1: Introduction
- Your body has many kinds of cells, each specialized for a specific purpose. Just as a home is made from a variety of building materials, the human body is constructed from many cell types. For example, epithelial cells protect the surface of the body and cover the organs and body cavities within. Bone cells help to support and protect the body. Cells of the immune system fight invading bacteria. Additionally, blood and blood cells carry nutrients and oxygen throughout the body while removing CO2
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- 2.2: Studying Cells
- This page outlines key learning objectives about cells and microscopy, underlining cells as fundamental life units. It distinguishes between prokaryotic and eukaryotic cells, discusses the differences in magnification and resolving power of light and electron microscopes, and reviews the historical development of cell theory. Additionally, it highlights the role of cytotechnologists in medical diagnostics through cellular examinations.
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- 2.3: DNA is Packaged into Chromatin
- If stretched to its full length, the DNA molecule of the largest human chromosome would be 85mm. Yet during mitosis and meiosis, this DNA molecule is compacted into a chromosome approximately 5µm long. Although this compaction makes it easier to transport DNA within a dividing cell, it also makes DNA less accessible for other cellular functions such as DNA synthesis and transcription.
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- 2.4: The Cell Cycle and Changes in DNA Content
- This page outlines the eukaryotic cell cycle, dividing it into four stages: Gap 1 (G1), DNA synthesis (S), Gap 2 (G2), and mitosis (M). It describes the sequence of events post-fertilization or cell division, including interphase comprising G1, S, and G2 phases. It also mentions the potential for cells to enter a non-dividing (G0) phase or undergo endoreduplication.
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- 2.5: Karyotypes Describe Chromosome Number and Structure
- This page explains karyograms as comprehensive representations of an organism's chromosomes, highlighting their importance in understanding genetic makeup and abnormalities. It notes that humans have 46 chromosomes, divided into autosomes and sex chromosomes, which are vital for sex determination.
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- 2.6: Chromosomes, Mitosis, and Meiosis
- Chromosomes contain genetic information. We often take this fact for granted, but just over a century ago, even the best biologists in the world were uncertain of the function of these rod-shaped structures. We now know that most chromosomes contain a single molecule of double-stranded DNA that form a complex with proteins. This arrangement allows long DNA molecules to be compacted into a small volume that can more easily be moved during mitosis and meiosis and expressed during interphase.
Thumbnail: Life cycle of the cell. (CC BY-SA 4.0; BruceBlaus).