Practical Biology U NIT 4: T HE C ELL C YCLE AND C ANCER

When demands are too high The result is Cell Division Cell Growth As cells get bigger it is more difficult for them to work: – – There is too much demand for information from the nucleus. – – It becomes too crowded and it is difficult to get materials in and out of the cell.

Cell Division in Our Bodies Brain cell - doesn’t divide in a life time Brain cell - doesn’t divide in a life time RBC’s days RBC’s days Skin cells - 35 days Skin cells - 35 days Stomach cell - 2 days Stomach cell - 2 days Bacteria cell - 20 to 30 minutes Bacteria cell - 20 to 30 minutes

A Review: Chromosomes Chromosomes are made of DNA packed around proteins called histones. Chromosomes are made of DNA packed around proteins called histones. The combination of protein and DNA is called chromatin. The combination of protein and DNA is called chromatin. Chromosomes are most visible during cell division. Chromosomes are most visible during cell division. A chromatid is one arm of a chromosome. A chromatid is one arm of a chromosome. The centromere is a spot in the center of the chromosome. The centromere is a spot in the center of the chromosome.

Chromosome Numbers Diploid (Somatic) cells Diploid (Somatic) cells –Most body cells (46 chromosomes) –2 of each chromosome type –homologous chromosomes - same genes different variations –Also called - 2n Haploid (germ) cells Haploid (germ) cells –Sperm and egg cells only (23 chromosomes) –1 of each chromosome –Also called 1n –Two haploid cells (egg and sperm) combine to create a diploid cell

Cell Division “All cells come from pre-existing cells” “All cells come from pre-existing cells” Prokaryotic cell division: Binary fission Binary fission

The Cell Cycle Cell grows Copies its DNA Divides nucleus and cytoplasm to form 2 daughter cells

The 3 Major Stages of the Cell Cycle Interphase Interphase: DNA is being replicated/Cell growth Mitosis Mitosis: the division of the cell nucleus Cytokinesis Cytokinesis: the division of the cytoplasm. M Phase

Interphase (Stage 1) G1 G1 – Cell grows and gets ready for DNA replication S phase S phase – DNA is replicated G2 G2 – Cell grows and gets ready for mitosis 3 Sub-Stages of Interphase

Mitosis (Stage 2) Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase Telophase PMAT! PMAT! 4 Minor Stages of Mitosis

Mitosis At the end of Interphase Prophase MetaphaseAnaphase Telophase Blood lilly Mitosis At the end of Interphase Prophase Metaphase AnaphaseTelophase

Prophase Chromatin chromosomes Chromatin coils up and becomes individual chromosomes Nuclear membrane breaks down Centrioles make spindle fibers Spindle fibers

Metaphase Chromosomes, Chromosomes, pulled by the spindle fibers, line up down the center of the cell.

Anaphase chromatids Chromosomes split into sister chromatids. Chromatids Chromatids are pulled to opposite ends of the cell by the spindle fibers.

Telophase Chromosomes Chromosomes are now at opposite ends of the cell Chromosomes Chromosomes unravel. Two new nuclear membranes form

Cytokinesis/Telophase (stage 3) Cytoplasm Cytoplasm pinches in half Cleavage Furrow Animals have a Cleavage Furrow cell plate Plants have a cell plate Daughter cells have identical sets of chromosomes

Do You Know the Stages of Mitosis? CYTOKINESIS PROPHASE ANAPHASE INTERPHASE METAPHASE TELOPHASE

Controls on Cell Division Most cells are in interphase Most cells are in interphase Checkpoints for division: Checkpoints for division: –Is DNA fully replicated? –Is the DNA damaged? –Are there enough nutrients to support cell growth? Cyclins – proteins that regulate the timing of the cell cycle Cyclins – proteins that regulate the timing of the cell cycle Mutations in these genes can lead to cancer

Genes Involved in Cell Cycle Internal Regulation (Cyclins) Tumor suppressor genes Tumor suppressor genes –Apoptosis – cell suicide (pre-programmed death) –Necrosis – cell death (un-programmed) outside source Proto-oncogenes – stimulate cell division but are easily mutated Proto-oncogenes – stimulate cell division but are easily mutated Cell Death Video

Cancer Definition: a group of more than 100 diseases that develop across time and involve the uncontrolled division of the body's cells Definition: a group of more than 100 diseases that develop across time and involve the uncontrolled division of the body's cells Extra cells form a mass or a tumor Extra cells form a mass or a tumor –Benign tumor remain within the mass (non-cancerous) –Malignant tumor cells invade and destroy healthy tissues elsewhere in the body (cancerous)

Types of Cancer Carcinoma- skin cells Carcinoma- skin cells Sarcoma- muscle, bone, cartilage, fat or connective tissues. Sarcoma- muscle, bone, cartilage, fat or connective tissues. Leukemia- white blood cells or their precursors (begins in bone marrow) Leukemia- white blood cells or their precursors (begins in bone marrow) Lymphoma- bone marrow cells/lymphatic system (solid tumors) Lymphoma- bone marrow cells/lymphatic system (solid tumors) Myelomas- affects white blood cells responsible for the production of antibodies Myelomas- affects white blood cells responsible for the production of antibodies Cell Cycle Animations Malignant Tumor Normal Cells Mastisized Tumor

What Causes Cancer? Gene changes due to: – – diet – – tobacco use – – exposure to radiation – – exposure to chemicals –(p53 or Rb don’t work) – Inherited genes (p53 or Rb don’t work) Immune System Failure Production of Telomerase Carcinogens

Allergic reactions – swelling – itching also flu like symptoms – greatest concern is extreme allergic reactions Biological Therapy: Elicits a response from your immune system (helps immune system fight cancerous cells) Weakening of the bones can - effect sex characteristics Hormone Therapy: Blocks hormones that cancer needs to grow Similar to radiation therapyChemotherapy: Chemicals target cancer cells given 2 or more at a time Can injure or kill healthy cells Radiation Therapy: Damages cancer cell’s DNA, cells won’t reproduce Restricted to a few types of cancer - may not get all cells- damages organsSurgery: physically remove tumor Side Effects Treatment

Cancer treatment and detection is improving Death rates decreased on average 2.1 percent per year from 2002 to 2004, nearly twice the annual decrease of 1.1 percent per year from 1993 through Death rates decreased on average 2.1 percent per year from 2002 to 2004, nearly twice the annual decrease of 1.1 percent per year from 1993 through Declines were observed in the incidence of lung cancer in men, colorectal cancer in men and women, and in breast cancer incidence in women from 2001 through 2004 Declines were observed in the incidence of lung cancer in men, colorectal cancer in men and women, and in breast cancer incidence in women from 2001 through 2004

Objectives Know what limits cell growth and know that these limits force a cell to divide. Define and distinguish between chromatin, chromosome, chromatid, and centromere. Define diploid, 2n, somatic cell and haploid, 1n, and germ cell. Be able to give the diploid number and haploid number for human cells. List the stages of the cell cycle and explain what occurs during each. Explain the differences between cytokinesis in plant cells and in animal cells. Explain how cell division is regulated. Define the following terms: cancer, oncogenes, tumor suppressor genes, malignant, and benign. Explain causes of cancer. Know the types of cancer. Explain five ways of treating cancer.