ChromosomesBinary Fission

MitosisCancer

CELL DIVISION

CHROMOSOMES

CHROMOSOMES

Are Tightly coiled strands of DNA and chromatin

- located in the nucleus of each cell- control growth and development

• Become darkly colored when stained.• Are the carriers of the genetic material that is

copied and passed from generation to generation of cells.

• Accurate transmission of chromosomes during cell division is critical.

CHROMOSOMES

CHROMOSOMES

Human Chromosome Number1. 46 total chromosomes2. Diploid cells = contain all 46 (full set) 3. Haploid cells = contain 23 (half set)

CHROMOSOMES

Two types of chromosomes1. Autosomes – 22 pairs2. Sex Chromosomes– 1 pair

B. Sex Chromosomesa. determine male or femaleb. XX = Femalec. XY = Male

CHROMOSOMES

• Chromatin – the relaxed, uncoiled state of the chromosome.

• Chromosome – threadlike structures within the nucleus containing genetic information that is passed from generation to generation.

Terminology

When chromosomes are preparing to divide the DNA replicates itself into two strands called chromatids.

Held together by a centromere

Binary Fission

CELL DIVISION IN

PROKARYOTES

• The process whereby bacteria copy their chromosome and then divide into two different cells.

BINARY FISSION

BINARY FISSION

MITOSIS AND MEIOSIS

CELL DIVISION IN

EUKARYOTES

CELL DIVISIONMitosis

• Occurs in body cells called SOMATIC CELLS• Examples

muscle cells, cheek cells, liver cells, bone cells, red blood cells, etc.

• Makes exact copies (asexual reproduction)

Meiosis• Occurs in sex cells

called GAMETES• Examples

egg cells, sperm cells• Mixes for genetic

variation (sexual reproduction)

Why must cells divide?

Cell division is necessary for:• Growth• Repair• Replacement of dying cells (such as skin

cells or red blood cells)• Reproduction of an organism.

• Most cells go through a series of changes in order to maintain homeostasis.

• Cells need to reproduce when their surface area can no longer supply the much larger volume with nutrients and rid wastes.

Cell Cycle The process of cell division is called the cell

cycle.

InterphaseThe first part of the cell cycle is called

Interphase

Interphase consists of three stages:-Normal cell activity-DNA (the chromosomes) replication-Final preparation for division

It is the longest phase of the cell cycle.

The Cell Cycle

Cell cycle The next phase of the cell

cycle is mitosis.

MitosisPurpose - to produce an exact copy of a

diploid cell.• After interphase, MITOSIS begins-4

phases(PMAT)–Prophase–Metaphase–Anaphase–Telophase

Cytokinesis in an Animal CellCleavage Furrow

Cytokinesis in an Plant Cell

Cytokinesis Cleavage furrow

Cell plate

Animal cell

Plant cell

Cell division

Which type of cells undergo mitosis?

Cell division

Which type of cells undergo mitosis?

All somatic cells.

Mitosis

Mitosis produces two exact copies of the original cell.

2 Diploid Somatic Cells

When Making New Cells Goes Terribly Wrong

MITOSIS AND CANCER

When is mitosis a BAD thing• When cells reproduce & they are not

needed– these cells take over organs, but don’t do the

right job– they just keep making copies– cancer

• damages organs

Why would cells just make copies?

• If DNA gets damaged, cells stop listening to correct instructions_Mutation: change in genetic makeup and

cause cells to become cancerous • Causes of mutations:

UV radiation chemical exposure radiation exposure heat

cigarette smoke pollution age genetics

Cancer-Causing Mutations• Exposure to environmental agents, virus, or

lifestyle changes may cause a mutation• Certain virus infections can transform the

cell • Human papillomavirus (HPV): Viral

proteins interact with cell proteins, cause cervical cancer

• Mistakes in DNA replication also cause mutations

Cancer• Carcinogens and certain behaviors

increase rate of mutations and cancer risk• Not all tumors are cancerous, benign

tumors, increase in size, but do not metastasize

• Metastasis: Process in which cells are invasive and move to other sites in the body

Cell Cycle Regulation• Normal cells contain check

points to regulate the cell cycle. Stopping at appropriate points.

• Cancerous cells do not respond to check points and continue rapidly through the cell cycle. This results in masses of undefined cells called tumors.

Tumors• Benign tumor

– abnormal cells remain at original site as a lump

– most do not cause serious problems &can be removed by surgery

Tumors• Malignant tumor

– cells leave original site• carried by blood system to other tissues• start more tumors

– damage functions of organs throughout body

Cancer Cells

Treatments for cancers• Treatments kill rapidly dividing cells

– chemotherapy• poisonous drugs that kill rapidly dividing cells

– radiation • high energy beam kills rapidly dividing cells

Cancer Is One Outcome of A Runaway Cell Cycle

Licentious division - prostate cancer cells during division.