Chapter 10 Cell Division

Prokaryotic Division Chromosomes (colored bodies) Prokaryotes have a single, circular chromosome

Prokaryotics Cell Division Prokaryotes (bacteria) reproduce through cell division Binary fission Circular chromosome (DNA) is replicated Replicated chromosomes are attached to the cell membrane at nearby sites As membrane expands, the copies separate New cell wall forms between copies, cell splits

What about eukaryotic division? Mitosis Eukaryotes use cell division to create new cells MITOSIS: division of the nucleus Growth, Maintenance and Repair Asexual cell division Reproduction MEIOSIS: a special, two-stage type of mitosis that results in daughter cells with half as many chromosomes as the parent cells

Humans 46 chromosomes Diploid state (2n = 46) 2 sets of 23 chromosomes (diploid) n = number of chromosomes in a set Fundamental number, haploid number In humans 23 n = contribution from each parent #23 = 1 sex chromosome, #1- 22 autosomes

Chromosomes Maternal Paternal Sex: X or X X or Y Autosomes #: ää 2222 (homologous pairs)

The Cell Cycle The Cell Cycle shows the stages of life of a cell

Cellular Division Cell division is how a cell makes a copy itself A cell spends most of its life in interphase 1st stage = G1, a growth phase; the number of organelles and the amount of cytoplasm double 2nd stage = S phase; DNA replicates (the chromatins turn into chromosomes) chromatins – loose uncoiled strands of DNA chromosomes – DNA wrapped around proteins How does DNA replicate? DNA Replication 3rd stage = G2, another growth phase; the cell will continue to grow

The Cell Cycle

Cellular Division After interphase, the cell goes through mitosis Mitosis is the next 4 phases of cellular division Mitosis occurs in all eukaryotic cells Only in your somatic cells Eukaryotic cells are cells that have a nuclei and membrane bound organelle Somatic cells are all body cells except for egg cells and sperm cells

Mitosis Overview

Phases of Mitosis First Phase – Prophase What happens during prophase? 1. Chromosomes condensed - become thicker 2. The nucleolus and nuclear membrane break down and disappear 3. Centrioles move to opposite sides of the cell 4. Spindle Fibers appear and radiate from the centrioles Spindle fibers are protein tubes

What does prophase look like?

Phases of Mitosis Second Phase – Metaphase What happens during metaphase? 1. Chromosomes move to the middle of the cell 2. Spindle fibers are attached to the chromosomes controlling their movement

What does metaphase look like?

Phases of Mitosis Third Phase – Anaphase What happens during anaphase? 1. The centromere breaks down The centomere holds the chromosomes together 2. The spindle fibers pull apart the chromosome Separating the sister chromatids

What does metaphase look like?

Phases of Mitosis Fourth Phase – Telophase What happens in telophase? 1. Nuclear membrane forms around chromatids This Forms a nucleus with a nucleolus 2. Chromatids turn into chromatins 3. The cell membrane starts to pinch inward to separate into 2 new cells 4. Centrioles and spindle fibers disappear

What does telophase look like?

Phases of Mitosis Cytokinesis is the last stage of cell division During cytokinesis the 2 cells actual split apart from each other In a plant cells, a cell plate grows between to the two new cell The cell plate develops into the cell wall

What does cytokinesis look like?