Cell Reproduction

Starting at the beginning… Biologically speaking, where did YOU come from? Biologically speaking, where did YOU come from?

Cells How many cells make up a human body? How many cells make up a human body? Did you have the same number last year? What about when you were 2 years old? 2 months old? Did you have the same number last year? What about when you were 2 years old? 2 months old?

Cells Your body is made up of between 10 and 100 trillion cells. (100,000,000,000,000) Your body is made up of between 10 and 100 trillion cells. (100,000,000,000,000) One-thousandth of them die every day One-thousandth of them die every day

Cells Where do all these cells come from? Where do all these cells come from?

Cell Reproduction

Cell Specialization Different body cells perform different functions Different body cells perform different functions Examples: skin, nerve, red blood cells, liver cells, platelets Examples: skin, nerve, red blood cells, liver cells, platelets

Cell Specialization Different cells live for different amounts of time Different cells live for different amounts of time (See chart, page 464.) (See chart, page 464.)464

Cellular Reproduction New cells are made from copies of old cells New cells are made from copies of old cells This process began occurring before you were born and will continue until after you die This process began occurring before you were born and will continue until after you die

Types of Cellular Reproduction MITOSIS – results in two identical cells; used for the majority of cells in the body MITOSIS – results in two identical cells; used for the majority of cells in the body MEIOSIS – results in four cells that are different from the “parents”; used for sex cells only MEIOSIS – results in four cells that are different from the “parents”; used for sex cells only

The life cycle of a cell

Mitosis Results in body growth or body repair Results in body growth or body repair Two new cells are called “daughter cells” Two new cells are called “daughter cells”

A Review of Cell Features Cell Membrane Cell Membrane Cytoplasm Cytoplasm Nucleus Nucleus Nuclear Membrane Nuclear Membrane Chromosomes – strands that carry a cell’s DNA Chromosomes – strands that carry a cell’s DNA Centrioles – strong, barrell-shaped organelle Centrioles – strong, barrell-shaped organelle

Mitosis Goals – duplicate chromosomes and move them to two new daughter cells Goals – duplicate chromosomes and move them to two new daughter cells

Before Mitosis Begins Chromosomes are duplicated within the cells (exact copies) Chromosomes are duplicated within the cells (exact copies) Held together at center Held together at center Two strands are called “sister chromatids” Two strands are called “sister chromatids”

Mitosis Step 1: PROPHASE Step 1: PROPHASE –Sister chromatids thicken –Nuclear membrane breaks down –Two centrioles move apart –Fibers (strands of protein) form between centrioles

Mitosis Step 2: METAPHASE Step 2: METAPHASE –Centrioles to opposite ends of cell –Fibers stretch between –Sister chromatids attach to fibers –Sister chromatids line up at center of the cell

Mitosis Step 3: ANAPHASE Step 3: ANAPHASE –Sister chromatids pulled apart from partner –Fibers pull chromatids towards centrioles at opposite ends of the cell

Mitosis STEP 4: TELOPHASE STEP 4: TELOPHASE –Each side now has complete set of chromosomes –Fibers disappear –Nuclear membrane re-forms –Cell membrane pinches inwards to form 2 cells

Cytokinesis The process of the cell membrane pinching together to fully separate into two new daughter cells. The process of the cell membrane pinching together to fully separate into two new daughter cells.

Mitosis in Plant Cells 2 Differences 2 Differences –No centrioles –Cell wall must re-form between new cells

Demo mitosis Use the lego to demonstrate Mitosis. Use the lego to demonstrate Mitosis. Have representations for: Have representations for: DNA DNA Chromosomes Chromosomes Centrioles Centrioles Spindles Spindles Cell membrane Cell membrane Nuclues Nuclues

Summary questions 1. Why do cells need to divide? (link back to SA:Vol ratio) 1. Why do cells need to divide? (link back to SA:Vol ratio) 2. How many times does the cell split 2. How many times does the cell split 3. How many daughter cells are created? 3. How many daughter cells are created? 4. What are the similarities between the daughter cells 4. What are the similarities between the daughter cells 5. Draw a replicated chromosome and label as many parts as you can. 5. Draw a replicated chromosome and label as many parts as you can.

INTERPHASE PROPHASE METAPHASE ANAPHASE TELOPHASE

Importance of Chromosomes All chromosomes come in pairs All chromosomes come in pairs Humans have 23 pairs, so a normal cell has 46 chromosomes Humans have 23 pairs, so a normal cell has 46 chromosomes All cells need a full set to function properly (except sex cells) All cells need a full set to function properly (except sex cells)

Chromosome Number Before mitosis begins, cells have two of each chromosome (2N) Before mitosis begins, cells have two of each chromosome (2N) After chromosomes duplicate, cells have four of each chromosome (4N) After chromosomes duplicate, cells have four of each chromosome (4N) After mitosis, cells have two of each chromosome (2N) After mitosis, cells have two of each chromosome (2N)

Meiosis

Meiosis Process that creates gametes (eggs and sperm) Process that creates gametes (eggs and sperm) Cells divide twice Cells divide twice

Chromosome Number Cells start with two of each chromosome (2N) Cells start with two of each chromosome (2N) Chromosomes double (4N) Chromosomes double (4N) Pairs divide (2N) Pairs divide (2N) Sister chromatids divide (N) Sister chromatids divide (N)

Importance of Meiosis During fertilization, sperm (N) and egg (N) fuse to create one cell (2N) During fertilization, sperm (N) and egg (N) fuse to create one cell (2N) New cell has complete set of chromosomes (half from mother, half from father) New cell has complete set of chromosomes (half from mother, half from father)

Chromosome Number N represents number of PAIRS of chromosomes N represents number of PAIRS of chromosomes 2N = total number of chromosomes in a normal cell 2N = total number of chromosomes in a normal cell N – total number of chromosomes in a gamete (sex cell) N – total number of chromosomes in a gamete (sex cell)

Steps of Meiosis Step 1 Step 1 –PROPHASE I

Steps of Meiosis Step 2: Step 2: –METAPHASE I

Steps of Meiosis Step 3: Step 3: –ANAPHASE I  Sister chromatids DO NOT separate. –TELEPHASE I

Steps of Meiosis Step 4: Step 4: –PROPHASE II –Cell has been split in two –No nuclear membrane forms

Steps of Meiosis Step 5: Step 5: –Occurs in both cells –METAPHASE II

Steps of Meiosis Step 6: Step 6: –ANAPHASE II –TELEPHASE II

THE MOST IMPORTANT DIFFERENCE In the first cell division, CHROMOSOME PAIRS are pulled apart. In the first cell division, CHROMOSOME PAIRS are pulled apart. In the second cell division, SISTER CHROMATIDS are pulled apart. In the second cell division, SISTER CHROMATIDS are pulled apart.

Cancer and Aging

Cancer/Aging How are cancer and aging similar? How are cancer and aging similar?

Cancer/Aging Changes in rates of mitosis Changes in rates of mitosis

Aging What properties of a person’s body change as they age? What properties of a person’s body change as they age? Physically? Physiologically? Physically? Physiologically?

Cancer Rapid, abnormal, uncontrolled mitosis Rapid, abnormal, uncontrolled mitosis What causes cancer? What causes cancer?

Cancer Causes Viruses Viruses Chemicals Chemicals Radiation Radiation