Cell Division and Mitosis

Starr/Taggart’s Biology:

The Unity and Diversity of Life, 9e

Chapter 9

Key Concepts:Continuity of life depends on

reproductionAfter cell division, each daughter cell

must receive the same amount of DNA

The cell cycle: Interphase and Mitosis DNA and proteins make up

chromosomes in eukaryotic cellsMembers of the same species have

the same number of chromosomes in their cells

Key Concepts:

The body cells of many organisms have a diploid chromosome number

Mitosis keeps the chromosome number constant

Mitosis is the basis of growth and tissue repair in multicelled eukaryotes.

Single-celled eukaryotes and many multicelled eukaryotes reproduce by mitosis

Overview

DNA contains hereditary instructions

Before cells reproduce, they must undergo nuclear division Mitosis

Meiosis

Multicelled organisms grow and repair themselves by mitosis

Overview

Mitosis and meiosis are nuclear division mechanisms

Mitosis in somatic cells allows growth, repair, and asexual reproduction

Meiosis occurs in germ cells, produces gametes, allows sexual reproduction

Prokaryotic cells reproduce asexually

Chromosomes

Each chromosome duplicates in preparation for mitosis

Sister chromatids remain attached

Mitosis and Chromosome Number

Chromosome number = Total of chromosomes in somatic cells Humans 46

Gorillas 48

Pea plants 14

Chromosomes are in pairs Humans 23 pairs

2n “diploid”

1n “haploid” (gametes)

The Cell Cycle

A diploid cell produces two diploid daughter cells

Two phases in cell cycle

InterphaseLongest phase

Increase in mass, doubles components, and duplicates DNA

MitosisNuclear division

InterphaseG1

“Gap” - cell growth before DNA replication

S

“Synthesis” - DNA replication

G2

“Second Gap” - preparation for division

The length of each part differs among different cell types

The Cell Cycle

Mitosis

Four stages

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis Cytoplasmic division

Prophase

Chromosomes become visible

Spindle apparatus formsCentrioles move apart to opposite poles

Microtubules break apart into tubulin subunits

New tubulin subunits form the spindle

Nuclear envelope breaks up

Prophase

Metaphase

Chromosomes interact with

microtubules on spindle apparatus Attachment at centromeres

•Kinetochore

Tubules pull on chromosomes

Orientation of sister chromatids to opposite poles

Alignment of chromosomes midway between the poles

Metaphase

Anaphase

Separation of sister chromatids Movement

toward opposite poles

Separation of Sister ChromatidsMicrotubules attached to

centromeres shorten and pull chromosomes towards poles

Separation of Sister ChromatidsSpindle elongates and the spindle

poles are pushed farther apart by overlapping microtubules

Telophase

Chromosomes arrive at spindle poles Chromosomes return to threadlike forms

New nuclear membranes form

Two nuclei form

Cytokinesis Division of cytoplasm

Forms two cells

Metaphase to Interphase

Cytoplasmic Division

Cytokinesis

Between late anaphase and end of telophase

In plants: cell plate formsVesicles fuse

In animals: cleavageCleavage furrow - depression forms at

cell’s midsection

In ConclusionA parent cell provides each daughter

cell with hereditary instructions

Eukaryotes divide by mitosis or meiosis and prokaryotes divide by binary fission

Each chromosome is one DNA molecule with proteins attached

Cells with a diploid number (2n) contain two of each kind of chromosome

In ConclusionMitosis maintains the chromosome

number from one cell generation to the next

Mitosis is the basis of growth and tissue repair, and asexual reproduction in some eukaryotes

The cell cycle includes interphase and mitosis

The phases of mitosis are prophase, metaphase, anaphase, and telophase

developed by M. Roig