“All cells arise from preexisting cells” (Virchow)

2 Types of Reproduction Asexual 1 parent No fusion of nuclei Offspring are identical to parent & to each other No special organs/cells Process that divides cells = mitosis In one-celled organisms = new organism In multi-cellular organisms = growth & repair Sexual 2 parents Fusion of sperm & egg nuclei Offspring have a combination of traits from both parents Requires special organs (gonads) & cells (gametes) Process that creates new cells = meiosis Produces sperm & eggs

Mitotic Cell Division Occurs in body cells, also called ________ cells Involves nuclear division, also known as __________ Involves cytoplasmic division also known as ___________ Results in ____ daughter cells __________ to the parent AND each other somatic mitosis cytokinesis 2 identical

Terms Associated with Mitosis Chromosomes: rod-like structures in nucleus that contain hereditary information (DNA) & appear as long, thin threads called chromatin (at rest) Diploid #: (2n) “having 2 sets of chromosomes” (body cells) Refers to total # found in somatic cells nucleus In humans, 2n = 46 Homologous chromosomes: the diploid # of chromosomes can be paired according to size. These pairs are called homologous. Each chromosome (homolog) of the pair controls the same set of traits

Terms cont. Monoploid #: (n) AKA haploid Having only one chromosome from each homologous pair Sex cells are monoploid Double-stranded vs. single-stranded: after mitosis, in order for the daughter cells to be identical to the parent in chromosome #, during the non-dividing period (interphase), each single-stranded chromosome makes an exact copy of itself, stays attached to the original, becoming a double stranded chromosome (this is NOT the same as being 1 member of a homologous pair)

The Cell Cycle and Mitosis The Cell Cycle: a series of events that cells go through as they divide

Laser clip

Interphase An “in between” period of growth Occurs right before mitosis Divided into 3 phases G1 (growth/pre-synthesis): (10+ hrs.) the cell ↑ in size & makes new proteins & organelles (centriole, spindle, aster) S (replication/synthesis): (9 hrs) chromosomes are replicated G2 (post-synthesis): (4 hrs) many organelles needed for cell division are produced (centrioles, spindles, aster) Then, mitosis (cell division) occurs with 4 remaining phases:

Prophase Chromatids coil & thicken Nuclear membrane & nucleolus disintegrate Centrioles move toward poles Asters & spindles form

Metaphase Meta = middle Chromatids line up in middle on “equator” Spindle fibers attach to centromeres

Anaphase “Away” Double chromatids are split into singles Spindle fibers shorten & pull chromosomes towards poles

Telophase Two new cells form by “furrowing” (pinching in AKA cytokinesis) Chromosomes uncoil back to chromatin Each new cell is now in interphase New nuclear membranes form

Results of Mitosis: 2 identical cells/ no variety Mitosis Maintains Chromosome #

Comparison of Plant & Animal Cell Mitosis AnimalPlant Centrioles?YesNo Division of the Cell cytokinesisCell plate formed/no furrowing

Uncontrolled division of abnormal cells = ______________ Uncontrolled division of normal cells = ________________ cancer tumor

Aging: the process of getting older Mitosis in some cells slows down or stops Why? Telomeres: “caps” of DNA found on the end of each chromosome Keeps the chromosome intact; functions like the plastic cap on the ends of shoelaces Each time a cell divides, telomeres get shortened, thus the cell ages (b/c a cell cannot divide anymore after telomeres are gone) divisions for a cell

Telomerase: enzyme that re-lengthens telomeres Present in high concentrations in embryonic stem cells, gametes (egg/sperm) & cancer cells Aging video..\biomovies \aging.mov..\biomovies \aging.mov

Types of Asexual ReproductionTypes of Asexual Reproduction link #2 link #2 TypeCharacteristicsRepresentative Organisms 1. Binary Fission Production of 2 new organisms with equal division of cytoplasm Ex. Paramecium

TypeCharacteristicsRepresentative Organisms 2. Budding The production of 2 new organisms w/ an unequal division of cytoplasm In coral, sometimes the bud stays w/ the parent & forms colonies (coral reefs) Ex. Yeast Ex. hydra 3. SporulationWhen spores are released from the parent & can develop into new organisms Ex. MoldMold

TypeCharacteristicsRepresentative Organisms 4. RegenerationThe development of an entire organism from a part of the original organism OR the replacement of lost structures An entire new starfish from 1 ray of the parent Ex. Lobster claws, lizard tails

Spiny Brittlestar Regenerating arm

TypeCharacteristicsRepresentative Organisms 5. Vegetative Propagation The process by which plants develop from roots, stems or leaves of the parent plant (asexually) See below a. Artificial propagation 1. cuttings: “cutting” from a plant that develops into a new plant 2. grafting: Taking a scion from a desirable tree & attaching it to a stock of another rooted tree

TypeCharacteristicsRepresentative Organisms b. Natural propagation1. Bulbs Short underground stem that grows a new plant Ex. Onion, tulip 2. Tubers Growing new plants from pieces of old plant Contains stored food Buds/eyes develop into new plant Ex. Potato 3. Runners When a plant sends a “runner” out which puts down roots & grows into another plant(s). Ex. Strawberry, pumpkin, squash