Unit 4 Genetics Ch. 10 Cell Growth & Division

Cell Growth  In most cases, living things grow by producing more cells  The cells of an adult animal are no larger than the cells of a young animal, there are just more of them  In most cases, living things grow by producing more cells  The cells of an adult animal are no larger than the cells of a young animal, there are just more of them

Limits to Cell Growth  There are 2 reasons why cells divide instead of continuing to grow indefinitely  The larger a cell becomes, the more demands it places on its DNA  Also, the cell has more trouble moving enough nutrients & wastes across the cell membrane  There are 2 reasons why cells divide instead of continuing to grow indefinitely  The larger a cell becomes, the more demands it places on its DNA  Also, the cell has more trouble moving enough nutrients & wastes across the cell membrane

Divisions of the Cell  Cell division - the process where a cell divides into 2 new daughter cells  Before cell division occurs, the cell replicates (copies), all of its DNA  Each daughter cell gets a complete copy of that genetic information  Cell division - the process where a cell divides into 2 new daughter cells  Before cell division occurs, the cell replicates (copies), all of its DNA  Each daughter cell gets a complete copy of that genetic information

Cell Division  Mitosis - the 1st stage, division of the nucleus  Cytokinesis - the 2nd stage, division of the cytoplasm  Mitosis - the 1st stage, division of the nucleus  Cytokinesis - the 2nd stage, division of the cytoplasm

Cell Division  Reproduction by mitosis is classified as asexual, since the cells produced by mitosis are genetically identical to the parent cell  It is also a source of new cells when a multicellular organism grows & develops  Reproduction by mitosis is classified as asexual, since the cells produced by mitosis are genetically identical to the parent cell  It is also a source of new cells when a multicellular organism grows & develops

Chromosomes  In eukaryotic cells, the genetic info passed from 1 generation of cells to the next is carried by chromosomes  Chromosomes are made up of DNA (which carries the cell’s coded genetic info) & proteins  In eukaryotic cells, the genetic info passed from 1 generation of cells to the next is carried by chromosomes  Chromosomes are made up of DNA (which carries the cell’s coded genetic info) & proteins

Chromosomes  The cells of every organism have a specific # of chromosomes  Every human cell (except sex cells), have 23 pairs of chromosomes or 46 individual chromosomes  The cells of every organism have a specific # of chromosomes  Every human cell (except sex cells), have 23 pairs of chromosomes or 46 individual chromosomes

Chromosomes  Before cell division, each chromosome is copied  Each chromosome consists of 2 identical “sister” chromatids  When a cell divides, 1 chromatid goes to each of the 2 new cells  Before cell division, each chromosome is copied  Each chromosome consists of 2 identical “sister” chromatids  When a cell divides, 1 chromatid goes to each of the 2 new cells

Chromosomes  Each pair of chromatids is attached at the center - centromere

The Cell Cycle  Interphase - the “in-between” period of growth  Cell cycle - the series of events that cells go through as they grow  Interphase - the “in-between” period of growth  Cell cycle - the series of events that cells go through as they grow

The Cell Cycle  During the cell cycle, a cell grows, prepares for division, & divides to form 2 daughter cells, each of which then begins the cycle again  The cycle consists of 4 phases  During the cell cycle, a cell grows, prepares for division, & divides to form 2 daughter cells, each of which then begins the cycle again  The cycle consists of 4 phases

The Cell Cycle  Mitosis & cytokinesis takes place during the M phase  Chromosome replication, or synthesis (to make), takes place during the S phase  When the cell copies the chromosomes, it makes a duplicate set of DNA  Mitosis & cytokinesis takes place during the M phase  Chromosome replication, or synthesis (to make), takes place during the S phase  When the cell copies the chromosomes, it makes a duplicate set of DNA

The Cell Cycle  Between the M and S phase are G1 and G2  The G phases are periods of intense growth  Between the M and S phase are G1 and G2  The G phases are periods of intense growth

Mitosis  Biologists divide the events of mitosis into 4 phases: prophase, metaphase, anaphase, & telophase  Prophase:  The 1st & longest phase of mitosis, when the chromosomes become visible  Centrioles - 2 tiny structures in the cytoplasm, separate & move to opposite sides of the nucleus  Biologists divide the events of mitosis into 4 phases: prophase, metaphase, anaphase, & telophase  Prophase:  The 1st & longest phase of mitosis, when the chromosomes become visible  Centrioles - 2 tiny structures in the cytoplasm, separate & move to opposite sides of the nucleus

Mitosis  Prophase:  The centrioles help to organize the spindle- a fanlike structure that helps separate the chromosomes  The nucleolus disappears, & the nuclear envelope breaks down  Prophase:  The centrioles help to organize the spindle- a fanlike structure that helps separate the chromosomes  The nucleolus disappears, & the nuclear envelope breaks down

Mitosis  Metaphase:  The 2nd phase of mitosis that only lasts a few minutes  The chromosomes line up in the middle  Metaphase:  The 2nd phase of mitosis that only lasts a few minutes  The chromosomes line up in the middle

Mitosis  Anaphase:  The 3rd phase of mitosis, when the centromeres split, allowing the sister chromatids to separate & become individual chromosomes  The chromosomes continue to move until they have separated into 2 groups at the poles  Anaphase:  The 3rd phase of mitosis, when the centromeres split, allowing the sister chromatids to separate & become individual chromosomes  The chromosomes continue to move until they have separated into 2 groups at the poles

Mitosis  Telophase:  The 4th & final phase of mitosis, a nuclear envelope begins to form around each cluster of chromosomes at the poles  The spindle begins to break apart, & a nucleolus becomes visible in each daughter cell  Mitosis is complete  Telophase:  The 4th & final phase of mitosis, a nuclear envelope begins to form around each cluster of chromosomes at the poles  The spindle begins to break apart, & a nucleolus becomes visible in each daughter cell  Mitosis is complete

Mitosis  Remember: IPMAT, (Interphase, Prophase, Metaphase, Anaphase, & Telophase)

Cytokinesis  As a result of mitosis, 2 nuclei (each with the same set of chromosomes) are formed, within the cytoplasm of a single cell  All that is left to complete the M phase of the cell cycle, is to divide the cytoplasm itself  As a result of mitosis, 2 nuclei (each with the same set of chromosomes) are formed, within the cytoplasm of a single cell  All that is left to complete the M phase of the cell cycle, is to divide the cytoplasm itself

Cytokinesis  Cytokinesis usually occurs at the same time as telophase

Cell Cycle Regulators  Cyclin - protein that regulates the cell cycle  Cyclins regulate the timing of the cell cycle in eukaryotic cells  Cyclin - protein that regulates the cell cycle  Cyclins regulate the timing of the cell cycle in eukaryotic cells

Uncontrolled Cell Growth  Cancer - disorder where some of the body’s own cells lose the ability to control growth  Cancer cells do not respond to the signals that regulate the growth of most cells  Cancer - disorder where some of the body’s own cells lose the ability to control growth  Cancer cells do not respond to the signals that regulate the growth of most cells