What you’ll learn about in this unit:

Why and how cells divide The three types of cell division: Binary Fission, Mitosis and Meiosis What regulates or controls when

cells start and stop dividing. How cells specialize during their

life Mistakes that occur during

division that can lead to cancer and genetic disorders

Unit 5 Cell DivisionKey Concept: All cells come from preexisting cells –

Cell Theory

Cell division – process by which cells produce new cells

3 Types of Cell Division: Prokaryotes (Bacteria) Eukaryotes (Animals, Plants, Fungi, Protists) Binary Fission Mitosis Meiosis

Purpose of Cell Reproduction /Division

Create new cells that contain the genetic material (DNA) stored in chromosomes.

Purpose of Cell Division

1. Binary Fission – Creates 2 genetically identical new

organisms by asexual reproduction

2. Mitosis – Creates somatic / body cells Ex. Skin, nerve, blood Used for growth, to repair damage or replace worn out cells

3. Meiosis – Creates gametes / sex cells Used for sexual reproduction

Chromosomes

When a new cell is made it must receive a copy of the genetic material from the parent cell.

Chromosomes are made of the DNA (genetic info) and“carry” it from a parent cell to the daughter cells.

Chromosome Location in Cells

Eukaryotic cells – Nucleus

Prokaryotic cells– Cytoplasm (Nucleoid Region)

Chromosome Shape Eukaryotic cells - Rod , Linear Prokaryotic cells – Circular

Chromosome Structure

2 Types of Molecules joined together

1. DNA (nucleic acid) 1 in each chromosome

2. Histones (protein) 1000’s in each chromosome

Two Types of Chromosomes

Autosomes – carry genes not related to sex Sex chromosomes – carry genes for sex traits

XX – Female XY - Male

Homologous Chromosomes

hair color

eye color

skin color

Homologous Chromosome Pair

One autosome from each parent Same size and shape Similar but not identical genes

Sex chromosomes are NOT homologous because they carry different genes

Body Cells and Sex Cells have different numbers of chromsomes

Somatic / Body Cells Have 2 copies of each chromosome 1 from

each parent – Diploid 2n

Members of a species have the same chromosome number in body cells

Ex. Humans 46 Dogs 78 Fruit Flies 4

Made through Mitosis

Body Cells and Sex Cells have different numbers of chromsomes

Gametes / Sex Cells Have only 1 copy of each chromosome -

Haploid 1n

Made through Meiosis

Haploid 1n Diploid 2n

3 Major Types of Cell Division

Binary Fission

* Used by Prokaryotes and some unicellular Protists * Makes two genetically identical daughter cells (clones) Form of asexual reproduction

Mitosis Used by eukaryotic organisms Process of making somatic/ body cells Ex Skin , nerve, muscle Used for growth, to repair damage or

replace worn out cells 2 Daughter cells are created from the

division on one parent cell Daughter cells are genetically identical to

the parent cell –they “inherit” an exact copy of the same chromosomes

Mitotic Cell DivisionX= Number of chromosomes

Parent Cell

X

Daughter Cells

X

X

Meiosis

Used by sexually reproducing eukaryotics. Process of making gametes/ sex cells.

4 new cells are made from one parent cell. New cells are NOT genetically identical to

the parent cell. Daughter cells have only half the number of

chromosomes as the parent cell.

Also known as Reduction Division

Meiotic Cell DivisionX= Number of chromosomes

Parent Cell

X

Daughter Cells

½ X

½ X ½ X

½ X

Gametes are made in Meiosis

DNA in threadlike form – Chromatin DNA in coiled /condensed form - Chromosome

Chromosome number is different in sex cells and body cells

• Haploid (n) cells have only 1 copy of each type of chromosome

• - Sex cells are haploid

• Diploid (2n) cells have 2 copies of each type of chromosome.– Body cells are diploid.

The zygote (fertilized egg) doubles its chromosomes and divides millions of times resulting in growth.Each new cell receives a complete set of all the chromosomes

6.1 Chromosomes and Meiosis

Meiosis occurs in the testicles and ovaries.

– Produces sex cells: egg and sperm.– Sex cells are what transport/carry the parents DNA to

their kids

body cells sex cells (sperm) sex cells (egg)

6.1 Chromosomes and Meiosis

• Haploid (n) cells have one copy of every chromosome.

– Gametes are haploid.– Gametes have 22 autosomes and 1 sex chromosome.

6.1 Chromosomes and Meiosis

• Chromosome number must be maintained in animals.• Many plants have more than two copies of each

chromosome.• Mitosis and meiosis are types of nuclear division that

make different types of cells.• Mitosis makes

more diploid cells.

6.1 Chromosomes and Meiosis

• Meiosis makes haploid cells from diploid cells.

– Meiosis occurs in sex cells. – Meiosis produces gametes.

Cell Division Vocabulary

diploid (2N) – a cell with 2 chromosome sets in each of its cells; all body (somatic) cells

haploid (N) – a cell with 1 chromosome set in each of its cells; all gametes (sperm, eggs)