Cell Reproduction: Process by which a cell divides and duplicates its genetic information Includes 2 stages: 1.Interphase: period of a cell’s life when it carries out its normal metabolic activities and grows; o chromosomes appear as chromatin(look like dots (chromosomes +proteins called histones) o Nuclear membrane is intact and visible as are the nucleoli BIOL 105 Lab 2--The Cell/Cell Division1 Lab 2, BIO 105

2.Mitotic phase –DNA and nuclear division into 2 daughter cells Is subdivided into four stages: --Prophase -- Anaphase --Metaphase -- Telophase just before nuclear division, chromatin condenses into chromatids (so they won’t break apart during division) and are held together by centromeres. PMAT – Mitotic phase is essential for body growth and tissue repair BIOL 105 Lab 2--The Cell/Cell Division2

Prophase—divided into 2 stages Chromosomes become visible, each with two chromatids joined at a centromere (Under the microscope, Chromosomes straighten out; are more disorganized looking ) DNA has replicated, but has not formed condensed structure of chromosome. They remain as loosely coiled chromatin; copies of chromatin remain attached to each other. chromatin Centrosomes separate, act as areas of growth of 2 “spindles” which migrate toward opposite poles of cell. Mitotic spindles (microtubules) form (from centrosomes) and push centrosomes toward opposite ends of cell Nuclear membrane is still intact to protect DNA molecules from mutation. BIOL 105 Lab 2--The Cell/Cell Division3

Metaphase Centromeres of chromosomes (called spindles) are aligned at opposite poles of cell Chromosomes line up at middle of the cell, called metaphase plate or equator or equatorial plate Anaphase Separated sister chromatids are pulled along behind centromeres and move to opposite cell ends. (“V” for victory sign)sister chromatids centromeres BIOL 105 Lab 2--The Cell/Cell Division4

Telophase Begins when chromosome movement stops Two sets of chromosomes uncoil to form chromatin New nuclear membrane forms around each chromatin mass Nucleoli reappear Spindle disappears Cytokinesis—division of cytoplasm so 2 new daughter cells are formed – Actually begins at end of Anaphase – Ring of actin microfilaments contracts to form a cleavage furrow and pinches apart so 2 daughter cells form BIOL 105 Lab 2--The Cell/Cell Division5

LABWORK 1. Identify the different stages of mitosis on microscope slides. 2. Describe process of DNA replication and mitosis. 3. Study process of mitosis models. [cell models] 4.Be able to identify interphase and each stage of mitosis on models and slides. BIOL 105 Lab 2--The Cell/Cell Division6