ch14imnoqs - Chapter14:CellularReproduction Cellular...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 14: Cellular Reproduction Cellular Reproduction: Background I. The 3rd tenet of Cell Theory – new cells originate only from other living cells; happens via cell division II. Multicellular organisms – countless divisions of a single-celled zygote produce an organism of astonishing A. Cell division does not stop with formation of mature organism, but continues throughout its life B. Tens of millions of cells undergo division at any given moment in an adult human 1. This amount of division is needed to replace cells that have aged or died 2. Old, worn-out blood cells are removed and replaced at the rate of ~100 million/minute 3. Importance of cell replacement becomes apparent after exposure to high radiation levels, which by radiation poisoning (like those who sealed Chernobyl) III. A. Mother cell transmits copies of its genetic information to its daughter cells, which become the next cell generation B. Daughter cells then become mother cells to their own daughter cells, etc. – thus the process is called cellular reproduction IV. Cell division occurs in all organisms, but is different in prokaryotes eukaryotes; this chapter concentrates on A. Cell division links parents to their offspring, living species to their extinct ancestors & humans to the earliest, most primitive cellular organisms The Cell Cycle: Introduction I. Cycle starts with cell division & ends with daughter cell formation or death – the stages through which a cell passes from one cell division to the next constitute the cell cycle II. Two major cell cycle phases - based on cell activities readily visible in light microscope A. M phase – M for "mitotic"; this stage includes mitosis (duplicated chromosomes are separated into 2 nuclei) & cytokinesis (entire cell & its cytoplasm divide into 2 daughter cells) 1. Only a small percentage of cells in a tissue or cell culture are seen to be in mitosis at any given time, suggesting that cells spend the majority of their time in interphase 2. In mitosis, the cell is focused on activities necessary for cell division; usually lasts only ~1 hour 3. 4. Length of M = % of cells in population in mitosis or cytokinesis x cell cycle length B. Interphase - occupies bulk of cycle: may extend for days, weeks or longer, depending on cell type & conditions; divided into G 1 2 (second gap) 1. Numerous preparations for upcoming mitosis occur during interphase, including replication of cell's DNA; cell often grows in volume during interphase 2. Does active metabolic functions (glucose oxidation, replication, transcription, translation) III. When does replication occur? – originally, it was thought that replication occurred throughout interphase; in
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 29

ch14imnoqs - Chapter14:CellularReproduction Cellular...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online