Cell Division

Cellular Reproduction Organism’s life begins as one cell

Rudolf Virchow (1858) stated: All cells come from cells

Prokaryotes divide only to reproduce

Asexual repro: 1 parent 2 daughters

AKA Binary fission (“dividing in half”)

One set of DNA duplicates, cell divides

Important Definitions

DNA: a molecule composed of deoxyribose nucleotides and contains the genetic information of living cells

Chromosome: a single DNA double helix together with proteins that help to organize the DNA

Chromatid: one of the two identical strands of DNA and protein that forms a replicated chromosome

Gene: a unit of heredity; specifies the amino acid sequence of proteins and hence particular traits

Allele: one of several alternative forms of a particular gene

Locus: the physical location of a gene on a chromosome

Important Definitions (cont.)

Diploid: referring to a cell with pairs of homologous chromosomes

Haploid: referring to a cell that has only one member of each pair of homologous chromosomes

Homologous Pair: two homologues that are similar in appearance and genetic information that pair during meiosis

Heterozygous: carrying two different alleles of a given gene

Homozygous: carrying two copies of the same allele of a given gene

What Are Mitosis And Meiosis?

Both are types of reproduction used during the cell cycle

Each type of cell division are specialized for different types of cells

Both undergo the cell cycle in very similar, yet very different ways

MitosisMitosis is the division of chromosomes in a cell

Usually followed by cytokinesis or cell division

Daughter cells produced after mitosis have same number of chromosomes as original cell

Purpose of mitosis is replication of somatic cells and asexual reproduction

Somatic cells include all cells in the body except the egg or sperm

MeiosisMeiosis is the division and reduction of the chromosomes of a cell

Daughter cells produced have half the chromosomes as the original cell

Purpose of meiosis is the production of gametes (sex cells)

Interphase And Synthesis Stages Of Mitosis And Meosis

During Interphase the cell carries out normal activities such as metabolism and protein synthesis

During synthesis the DNA in each chromosome is replicated

(GUEST, 2009)

Eukaryotic cells divide for reproduction, growth, and replacement of cells

Other organisms (plants & animals especially) reproduce through sexual reproduction

Sperm + Egg offspring

Offspring gets two

sets of genetic

information, one

from each parent

The Chromosome DNA is contained in structures called chromosomes within the nucleus of the cell

“chroma” color, “soma” body

Most of the time, chromatin fills the nucleus

Tangled mass of fibers of DNA & protein

When a cell begins to divide, the chromatin condenses and coils into chromosomes

Each chromosome has one long DNA molecule containing thousands of genes

The Chromosome Before a cell divides, it must duplicate its chromosomes

DNA replication!

Once duplicated, the chromosomes have sister chromatids with identical genes, joined at a centromere

When the cell divides, half goes to each daughter cell

The Cell Cycle Sequence of events from the time a cell divides to when it forms two daughter cells

Serves to double the cell’s parts, then splits

Stages:

Interphase 90%

Mitotic phase 10%

(SMITH, 2010)

Mitotic Phase Unique to eukaryotes

Ends with 2 identical cells

Sub-stages of Mitosis:

Prophase

Metaphase

Anaphase

Telophase

Cytokenisis

Prophase Sister chromatids are attached at centromere

Centrioles separate and extend spindle fibers

Nucleolus disappears and nuclear envelope breaks down

Kinetochores form on each chromatid, spindle fibers attach

Metaphase Centrosomes at poles

Chromosomes lined up at metaphase plate (cell’s equator)

Kinetochores of sister chromatids face opposite poles

Prophase And Metaphase Stages of Mitosis

The prophase stage

chromosomes condense and would be visible under a light microscope

the nuclear membrane degrades

In the metaphase stage the chromosomes line up along the equator

(PATTERSON, 2008)

Bibliography

 

GUEST. (2009). MITOSIS. MITOSIS. CHICAGO: SHARESLIDES.

TAMARITA. (2008). MITOSIS FINAL. MITOSIS FINAL. NEW YORK: SHARESLIDES.

JACKSON. (2010). BIOLOGY MITOSIS. BIOLOGY MITOSIS. LONDON: SHARESLIDES.

MARGLEMA. BIOLOGY MITOSIS INTERACTION. BIOLOGY MITOSIS INTERACTION. NEW YORK: SHARESLIDES.

PATTERSON, C. (2008). THE CELL CYCLE. AN OVERVIEW OF THE CELL CYCLE. BOSTON: SHARESLIDES.

SMITH. (2010). BIOLOGY-MITOSIS. BIOLOGY MITOSIS. LONDON: SHARESLIDES.