CYCLE CELL

Cell division results in two new cells identical to the original cell The original cell is called the parent cell.

Chromosomes – Rod-shaped structures that contain DNA and proteins Chromosomes become darkly-colored when stained Chromosomes carry the genetic material that is copied and passed from generation to generation of cells. What is an example of genetic material???

Supercoil within chromosome The structure of eukaryotic chromosomes Sister chromatids Centromere Supercoil within chromosome Chromosome Continued coiling within supercoil Histone (protein) DNA Section 8.2 Summary – pages 201 - 210

The DNA (chromatin) wraps tightly around proteins called histones. Purpose? Histones help maintain the shape of the chromosome.

Chromosomes consist of two identical halves Chromosomes consist of two identical halves. Each half is called a chromatid. Centromere – attachment point of the 2 chromatids

Each species has a certain number of chromosomes in each cell. For example, humans have 46 chromosomes in each cell.

2 types of chromosomes 1. Autosomes – all chromosomes that aren’t sex chromosomes. (#) 2. Sex chromosomes – determine the sex of an organism, but can also carry other traits. (Human sex chromosomes are X and Y) Females normally have 2 X chromosomes Males normally have 1 X and 1 Y

Karyotype: What do you notice about the X and Y? Each body cell of an organism produced by sexual reproduction has 2 copies of each autosome. Karyotype:

Haploid or diploid? Haploid – cells that contain only one set of chromosomes. These have half the number of chromosomes found in diploid cells Ex: sex cells 1n Diploid – cells that contain 2 chromosome sets. Ex: body (somatic) cells 2n * Note: meaning of somatic

Cell Division in Prokaryotes …called binary fission. The result is new material that is identical to the original cell.

Cell division in eukaryotes is called MITOSIS and is part of the larger CELL CYCLE Cell division is only one phase of the cell cycle. The cell spends the rest of its life in other phases. The CELL CYCLE refers to the processes of interphase and cell division in eukaryotes

Cell Cycle The majority of a eukaryotic cell’s life is spent in the growth period known as interphase. In INTERPHASE the cells grow, copy DNA, and prepare for cell division. eukaryotes

Interphase, the busiest phase of the cell cycle, is divided into four parts – three growth parts and one dormant period. What’s a dormant period?

Four Phases of Interphase G1 – cell growth – cells grow to mature size S – DNA copied G2 – preparation for cell division G0 – dormant period – cells have reached maturity and never divide again *** Not all cells will go into the G0 phase.

Following interphase, a cell enters its period of nuclear division called mitosis.

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

Prophase: The first phase of mitosis During prophase, the chromatin coils to form visible chromosomes. Spindle fibers begin to form Nuclear envelope begins to disappear Chromosomes are doubled

Chromatin – the uncoiled (loosely-packed) DNA in cells NOT undergoing cell division Sister Chromatids - the two halves of the doubled structure. Sister chromatids

Remember… Sister chromatids are held together by a structure called a centromere, which plays a role in chromosome movement during mitosis. Centromere – attachment point of sister chromatids Centromere

More about the Spindle...

Explain the terms: Spindle mIcrotublues Centrioles Kinetochore

Prometaphase (step 1.5) Nuclear envelope finishes breaking down Spindle finishes forming: Kinetochores Microtubules Spindle fibers arrive at poles

Metaphase: The second stage of mitosis During metaphase, the chromosomes line up on the equator of the spindle. Centromere Spindle fibers Sister chromatids

Anaphase: The third phase of mitosis During anaphase, the centromeres split and the sister chromatids are pulled apart to opposite poles of the cell.

Telophase: The fourth phase of mitosis During telophase, two distinct daughter cells can be seen. Nuclear envelope reappears Two daughter cells

Cytokinesis Following telophase, the cell’s cytoplasm divides in a process called cytokinesis. After this, the cells go on to do interphase again. Cytokinesis differs between plants and animals. Toward the end of telophase in animal cells, the plasma membrane pinches in along the equator.

Cytokinesis – plant vs. animal Animal Cell - the area of the cell membrane that pinches in and eventually separates the dividing cell into two cells is called the cleavage furrow

Cytokinesis – plant vs. animal Plant cells have a rigid cell wall, so the plasma membrane does not pinch in. A cell membrane forms around each cell, and new cell walls form on each side of the cell plate until separation is complete.

Do you think that cell cycle length can vary or is it always the same?

What controls cell division? A cell spends most of its time in interphase…so how does it know when to move on to cell division? PROTEINS regulate at certain checkpoints: G1 – cell growth checkpoint G2 – DNA synthesis checkpoint Mitosis checkpoint

checkpoints G1 (cell growth) checkpoint – if the cell has grown enough, proteins initiate the S Phase

checkpoints G2 (DNA synthesis) checkpoint – DNA repair enzymes check the results of the DNA replication. If inspection is passed, cell can proceed to mitosis

checkpoints Mitosis checkpoint – if mitosis has occurred correctly, proteins signal the cell to exit mitosis and re-enter G1.

What if a cell fails inspection? That cell passes into the G0 phase. Most cells that go to this phase stay there permanently.

When Control is Lost… The proteins that regulate cell growth and division are coded for by genes. Mutations occur and the cell doesn’t function properly A disruption could lead to cancer – uncontrolled growth of cells

How might proteins be connected to cancers?

Results of Mitosis When mitosis is complete, unicellular organisms remain as single cells. In multicellular organisms, cell growth and reproduction can result in groups of cells that work together as tissue to perform a specific function.

Tissues organize in various combinations to form organs that perform more complex roles within the organism. Multiple organs that work together form an organ system.

Let’s watch… 2:47

Question 1 A. centromeres B. chromosomes C. genes D. chlorophylls The stringy, rod-like structures in the cell nucleus that contain DNA are __________. A. centromeres B. chromosomes C. genes D. chlorophylls Section 2 Check

Question 2 A. prophase C. anaphase B. metaphase D. telophase Look at the diagram and identify the stage of mitosis that is depicted. Centromere Sister chromatids A. prophase C. anaphase B. metaphase D. telophase

Question 3 A. cytokinesis B. telekinesis C. meiosis D. mitosis What is the process by which a cell's cytoplasm divides? A. cytokinesis B. telekinesis C. meiosis D. mitosis Section 2 Check

Question 4 A. organ systems B. organs C. tissues D. cell cycles In multicellular organisms, groups of cells that work together to perform a specific function are called __________. A. organ systems B. organs C. tissues D. cell cycles

Question 5 Magnification of a plant cell reveals centromeres that have split and sister chromatids being pulled to opposite poles of the cell. This cell is in which phase of mitosis? A. prophase B. metaphase C. anaphase D. telophase Chapter Assessment

Disappearing nuclear envelope Question 6 Which phase of mitosis is depicted in this diagram? Spindle Fibers Doubled chromosome Disappearing nuclear envelope A. prophase C. anaphase B. metaphase D. telophase

Question 7 What is the term used for the period of the cell cycle represented by the red arrow in this graph? A. prophase DNA synthesis and replication B. metaphase Centrioles replicate; cell prepares for division Rapid growth and metabolic activity C. centrophase D. interphase Mitosis Cytokinesis Chapter Assessment

Question 8 What is the level of organization that is missing in this diagram? ? Cell Organ (muscle cell) Organ System Organism (stomach) (digestive tissue) (Florida Panther) A. mass C. tissue B. cluster D. cycle Chapter Assessment

Question 9 Which structure represents a cell in prophase of mitosis? B C D A. A C. C B. B D. D Chapter Assessment