CELL GROWTH & REPRODUCTION

Cells cannot grow indefinitely ... they can mature, then divide or die If the cell is going to divide, new cells need both *cytoplasm (cytokinesis =division of cytoplasm) *copies of nuclear material In unicellular organism, reproduction=cell division In multicellular organism, cell reproduction allows growth, replacement of cells that wear out (skin, blood, etc), not reproduction of whole organism

Mitosis Mitosis- the process by which the nucleus of a cell divides, while maintaining the chromosome number. Cytokinesis- the division of the cytoplasm of the cell after mitosis or meiosis.

Mitosis Define Mitosis Define Cytokinesis Mitosis is essential for growth & repair of an organism It is the process that distributes the genetic material evenly between two daughter cells, so that each daughter cell is genetically identical to the parent cell. It’s simply a way to make more of the same cell

In animals… Somatic cells (cells of the body) are diploid. This means that each cell has two chromosomes of each type. They are in PAIRS. Biologists use “2N” to symbolize diploid. Gamete cells (egg, sperm) are haploid. This means that each cell has only one of each type of chromosome. Biologists use “1N” to symbolize haploid.

MITOSIS When somatic cells reproduce themselves the process is called MITOSIS. Mitosis leads to the production of two “daughter cells”. Each daughter cell has the same number of chromosomes as the parent cell. 2N Parent Cell Daughter Cells

ID each of these DNA Chromosomes Chromatin

Replicated Chromosomes Sister chromatids Bound at center by centromere Chromatids are identical Product of DNA replication How many chromatids are in a human cell that is going through Prophase & Metaphase??? centomere chromatid

Homologues versus chromatids Homologous chromosomes One from Mom and One from Dad Have different versions of the same genes Sister chromatids Bound at center by centromere Chromatids are identical Product of DNA replication

Chromosomes What’s a homologous pair? Chromos’ that code for the same traits They code for the same traits but each member of the pair has different information (different versions of the same genes)

Chromosomes (n) n refers to the number of pairs (or the number of different types of chromosomes) 2n refers to the total number of chromosomes In humans n = 23 In chimpanzees n = 24 In the king crab n = 104

Phases of Mitosis

Mitosis Interphase Prophase Metaphase Anaphase Telophase REPEAT (This process produces two identical cells. The process then repeats for each of the new cells.)

Mitosis

Mitosis Interphase Prophase DNA replication Centrioles replicate & become visible Cell spends most of life carries on 8 life processes (all but reproduction) Prophase Chromatin condenses become visible as sister chromatids (chromosomes) Centrioles move toward the poles Asters & Spindle form Nuclear membrane disappears

Metaphase Anaphase Centrioles at opposite poles Chromosomes line up at metaphase plate/equator Each replicated chromosome is attached to one the spindle at the centromere Anaphase Each of the sister chromatids separate at the centromere and move toward the opposite poles of the cell

Mitosis Telophase Cell divides  2 identical copies New Interphase begins And the process starts all over in each daughter cell Telophase Chromosomes decondense to chromatin Formation of cleavage furrow (animal cell), or cell plate (plant cell) spindle disappears New nuclear membranes forms the cytoplasm divides in two, this is called cytokinesis

INTERPHASE - DNA replicates centrioles The steps of Mitosis: INTERPHASE - DNA replicates centrioles rep`licate; cell spends most of life (carries on all life processes except reproduction) PROPHASE - chromatin condenses into discrete chromosomes, centrioles move to poles, spindle forms; nuclear membrane disappears METAPHASE – chromosomes (attached to spindles @ centromere) are lined up at the equatorial plane (in the middle) ANAPHASE - Sister chromatids separate at the centromere and migrate to opposite poles. TELOPHASE - chromosomes decondense to chromatin, a cleavage furrow deepens in the middle of the cell, nuclear membranes form, spindle disappears. Finally, the cytoplasm divides in two, this is called cytokinesis. 2 form identical cells, Interphase begins.

Plant Mitosis vs. Animal Mitosis

Reproduction Asexual reproduction (1 parent gives rise to 1 or more clones) Offspring are identical to the parents (Identical hereditary information) Accomplished by mitosis and cytokinesis Types of Asexual Reproduction What are some examples of organisms that reproduce asexually?