Mitosis B Mitosis and cytokinesis produce two genetically

Mitosis

B. Mitosis and cytokinesis produce two genetically identical daughter cells 1. Interphase - important role in preparing cell to divide (2 sets of DNA and are large enough) 2. Mitosis - divides cell’s nucleus into two genetically identical nuclei, each with its own single, full set of DNA Two genetically identical nuclei

Cell Division • Interphase • Mitosis – Prophase – Metaphase – Anaphase – Telophase • Cytokinesis

Interphase • Most of the cell cycle is spent in interphase • G 1, S, G 2 • DNA is in the form of chromatin • Cell is preparing to divide (replicates DNA)

Early Prophase • Chromatin in nucleus condenses to form visible chromosomes • Mitotic spindles form from fibers in cytoskeleton or centrioles (animal)

Late Prophase • Nuclear membrane & nucleolus broken down • Chromosomes are clearly visible • Spindle fibers called kinetochores attach to the centromere of each chromosome • Spindle finishes forming between the poles of the cell • Longest phase of mitosis (50 -60%)

Spindle Fibers • The mitotic spindle forms from the microtubules in plants and centrioles in animal cells • Polar fibers extend from one pole of the cell to the opposite pole • Kinetochore fibers extend from the pole to the centromere of each chromosome • Asters are short fibers radiating from centrioles

Metaphase • Chromosomes, attached to the kinetochore fibers, move to the center of the cell • Chromosomes are now lined up at the equator • Shortest phase of mitosis (<10%)

Anaphase • Sister chromatids are pulled to opposite ends of the cell by kinetochore fibers • Centromeres divide in two

Telophase • Sister chromatids at opposite poles • Spindle disassembles • Nuclear envelope forms • Nucleolus reappears • Cytokinesis occurs • Chromosomes unwind as chromatin

Cytokinesis • Cytoplasm is divided into two identical daughter cells • Animal cells – Cell pinches in half, forming a cleavage furrow • Plant cells – Cell plate forms between two nuclei

Mitosis • Results in two identical daughter cells – Have the same number of chromosomes as parent cell (diploid) – Smaller than parent cell—must grow in size to become mature cells (G 1 of interphase)

Name the Stages of Mitosis: Early Anaphase Early prophase Metaphase Interphase Late Prophase Late telophase, Advanced cytokinesis Early Telophase, Begin cytokinesis Mid-Prophase Late Anaphase 19

Identify the Stages ? Early, Middle, & Late Prophase ? ? Metaphase Late Prophase Anaphase ? ? Late Anaphase ? Telophase ? Telophase & Cytokinesis 20

b. Asexual reproduction - creation of offspring from a single parent. Offspring genetically identical

2. Binary fission - asexual reproduction of singlecelled organism a. Occurs in prokaryotes b. binary fission and mitosis have similar results

B. Advantages and Disadvantages of Asexual reproduction 1. In environments that don’t change, asexual may be better. If they are well suited to environment may be more efficient 2. In changing environments sexual reproduction produces genetic diversity which raises chances for survival