Centrosomes organize microtubules Centrioles: bundles of microtubules – Pull chromosomes, form core in cilia Centrosomes and Centrioles

Cilia and Flagella Motor proteins 2:9 microtubule pattern Cilia move fluids Flagella move sperm cell

Internal lumen and membranes for protected reactions Mitochondria: Generates cell energy (ATP), have DNA Membranous Organelles: Create cell compartments

Smooth ER: Lipid synthesis & conversion Rough ER: Ribosomes, protein assembly & transport vesicles Endoplasmic Reticulum (ER) & Ribosomes

Cell Growth and Reproduction Cell Cycle- the series of changes Two Phases – Interphase: Cell grows and carries on its usual activities – Cell division or mitotic phase: cell divides into two daughter cells

G 2 Very brief. Enzymes and other proteins synthesized. By the end, centriole replication is completed Cell Life Cycle: Interphase or Growth Phase (G1, S, G2) - “between- phases”, prepares for mitosis by duplicating DNA and organelles S phase: DNA replication. New histones are made and assembled into chromatin G 1 : The cell is metabolically active, synthesizing proteins and growing

Mitosis: Reproduction of DNA nuclear division for all somatic or body cells diploid cells (2N) result in making 2 diploid daughter cells (2N). Four stages – Prophase – Metaphase – Anaphase – Telophase

Prophase = puddle of DNA “before-phase” chromatin shorten into chromosomes centrioles move to opposite ends, spindle fibers form nuclear envelope and nucleolus disappear

Metaphase: Middle “middle-phase” chromosomes line up on equatorial plate centromeres attach to fibers

Anaphase: Apart “apart phase” chromosomes split and chromatid is pulled to opposite centrioles spindle fibers shorten

Telophase: Tearing “end phase” chromosomes elongate to chromatin nuclear envelope and nucleolus reappear Cytokinesis: allows cell membrane to pinch in to separate 2 new daughter cells – Separate from Telophase

Cell Division Mitosis: division of the nucleus Cytokinesis: division of the cytoplasm The amount of nutrients a growing cell requires is directly related to its volume

Regulators of Cell Division 1.Chemical signals ( growth factors, hormones) released by other cells 2.Availability of space: Normal cells stop proliferating when they begin touching ( contact inhibition) 3.Cyclins and Cdks: proteins that allow the cell to enter S phase

Meiosis: Reproduction of Sex Cells A. Provides genetic variation in offspring because daughter cells are haploid (1N), where parent cells were diploid (2N). B. Chromosomes exist in pairs called homologous pairs; one from each parent.

1. Two kinds of chromosomes: 1.*autosomes- #s 1-22; determine body characteristics 2.*sex chromosomes- #23; determine if male (XY) or female (XX) 2. Somatic cells contain the diploid number of chromosomes, 2N = 46 for humans. 3. Gametes contain the haploid number of chromosomes, which is ½ the diploid number, 1N = 23 for humans.

Meiosis I – reduction of chromosomes 4 phases- 1. Prophase I- homologous chromosomes pair up, called tetrads; crossing-over? 2. Metaphase I- homologous pairs line up on equatorial plate 3. Anaphase I- homologous pairs split, each chromosome moves to opposite centrioles 4. Telophase I – cytokinesis occurs to separate into 2 daughter cells

Meiosis II division of chromosomes, similar to mitosis except the 4 phases are II. Result  4 haploids cells (1N). In male, generate 4 sperm. In female, generate 1 large egg Diploid Cells (2N)  Meiosis  Haploid Cells (1N)  Fertilization of 1N Egg + 1N Sperm = 2N Zygote

Three sources of genetic variability: 1.Independent assortment of homologues- combination of maternal and paternal chromosomes in gametes is 2 23 or 8 million. 2.Crossing over- genes on other chromosomes can stick 3.Random fertilization – which sperm wins?