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biology_chapter_6_notes1.docx

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Department
Biology
Course
BIOL 1500
Professor
All Professors
Semester
Winter

Description
Biology Chapter 6 Notes: Chromosomes and Cell Division • Telomere: cell reproduction "counter" and human cells divide about 50 times • Some chromosomes are circular, some are linear; • Binary fission (division of 2): asexual reproduction of prokaryotic cell division; daughter cells inherit their DNA from a single parent cell; DNA is carried in a single, circular chromosome; begins with replication (DNA duplicates itself); DNA molecule unwinds from its coiled-up configuration; the DNA strand splits apart and free-floating nucleotide bases attach; the cell elongates and pinches into two • Eukaryotic chromosome: made of more than just DNA; the long linear DNA strand is wrapped around proteins called histones (keeps DNA from getting tangled) Cell Cycle • eukaryote cells: somatic cells are cells forming the body of the organism and gametes are reproductive sex cells • Two phases to the somatic cell cycle: cells grow and prepare to divide during interphase and divide during the mitotic phase Interphase • Gap 1: cell grows and performs all cellular functions (making proteins, getting rid of waste, etc); cells that divide infrequently (neurons, heart muscle cells) spend most of their time in Gap 1 • DNA synthesis: cells begin to prepare for cell division; every chromosome creates an exact duplicate of itself by replication; before replication, each chromosome has become a pair of identical long linear strands, held together near the centre (region where chromosomes are in contact is called centromere) • Gap 2: cells continue to grow and prepare for cell division; differs from Gap 1 because genetic material has now been duplicated; Gap 2 usually shorter than Gap 1 Mitosis • nucleus of parent cell duplicates; followed by cytokinesis • DNA replication: Unwinding of coiled double-stranded DNA molecule and Rebuilding of double stranded DNA with an enzyme connecting the complementary base pairs • Purpose: enable existing cells to generate new, identical cells for Growth and Replacement • Apoptosis: Cells that must be replaced die on purpose 1. Prophase: nuclear membrane breaks down; sister chromatids (replicated chromosomes) condense; spindle fiber forms 2. Metaphase: sister chromatids line up at the centre of the cell 3. Anaphase: the sister chromatid pairs are pulled apart by the spindle fibrers; one full set of chromosomes from each chromatid goes to each side of the cell 4. Telophase: chromosomes begin to uncoil; nuclear membrane is reassembled around them 5. Cytokinesis: cytoplasm and organelles duplicate and are divided into approximately equal parts Out of Control Cell Division • Cancer: unrestrained cell growth and division and can cause serious health problems • Loses their "contact inhibition" • Cancer cells can divide indefinitely • Benign vs. malignant; metastasis is the process cancer cells separate from a tumor and invade the circulatory system Meiosis • Fertilization: fusion of two reproductive cells • Outcomes: 1. Redu
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