A CELL’S ROLE IN CREATING AN ORGANISM

Uni-cellular organism Organism is composed of a singe cell Single cell performs all life functions Examples: yeast, bacteria

Multicellular Organisms Organism composed of more than one cell Examples: plants, animals Cells develop special jobs and group together in an organized way...

Mutlicellular Organism Levels of organization cells --> tissues --> organs --> organ systems --> organisms

Cells Are the basic unit of structure and function in living things Examples- blood cells, nerve cells, bone cells, etc

Tissues Made up of groups of similar cells that perform a particular function Examples— connective, epithelial, muscle, and nerve

Organs Made up of tissues that work together to perform a specific activity Examples - heart, brain, skin, etc.

Organ systems Groups of two or more organs that work together to perform a specific function for the organism. --Examples - digestive system, nervous system, skeletal system, etc.

Organism Entire living thing that can carry out all basic life processes

Essential Question How do organisms get to be MULTI-cellular?

Cell growth and Division Why can’t cells get infinitely large? 1. Because the info stored in DNA can only meet the needs of a limited sized cell... Too big of a cell leads to an “information crisis”

Why can’t cells get infinitely large? 2. Because a cell that is too big can not efficiently have nutrients delivered and wastes removed

Diffusion and Cell Size Lab

Limits to cell size DNA overload Problems exchanging materials Ratio of surface area to volume

Surface Area

Do Now….. 1) List the levels of organism organization from smallest to largest 2) Why can’t cells get infinitely large? 3) Are the cells of an elephant larger than the cells of a mouse? Why or why not?

How do cells divide? Cell division is a pattern of growth and division for the cell. The cell will grow so that when it divides it will be the proper size and the new cell will have all of the “parts” that it needs. Cells will continue to do this until they die

The cell cycle focuses on what happens in the nucleus……. So lets first get to know the terms associated with our DNA.

Every cell has 6 feet of DNA inside its nucleus!

How does the cell fit 6 ft of DNA in a nucleus? The DNA is tightly packaged inside the nucleus. We will see how this works on the next slide.

Chromatin: DNA and proteins spread out loosely in the nucleus Like a bowl of spaghetti

Chromosome: Long, rod-shaped structures composed of DNA and proteins Duplicated Chromosome: Even when it is duplicated it is still considered a chromosome…..just duplicated *Each arm is now called a sister chromatid held together at the centromere *ONLY IN THIS STAGE WHEN THE CELL IS DIVIDING!

Chromosome Structure: Super Coiling of DNA (YouTube Clip—click image)

Chromosomes are formed from a single DNA strand that contains MANY genes  NOTE: Gene = a region of DNA that controls a hereditary characteristic (trait)

46 1 chromosome = 1-strand of DNA  How many strands of DNA do we have in a normal body cell? Click for size perspective

1.Every species has a set number of chromosomes in each cell 2.Humans have 46 chromosomes (23 pairs) in EVERY cell with the EXCEPTION of sex cells

Do you think that the number of chromosomes indicates how highly developed an organism is? Check out other organisms !

1. SEX CHROMOSOMES – chromosomes that determine the sex of an organism – Humans…Normal Female = XX Normal Male = XY – Chromosome pair #23 2. AUTOSOMES All of the other chromosomes in an organism. Chromosome pairs #ed 1-22

Organisms receive one copy of each autosome from each parent So we have 23 pairs! One from mom and one from Dad The two copies of each autosome are called HOMOLOGOUS CHROMOSOMES Their “bands” line up!

HOMOLOGOUS CHROMOSOMES = chromosomes of the same size, shape, and banding pattern. One chromosome of the pair came from each parent.

1.Haploid (1n) = cells that contain ONE SET of chromosomes (germ cells/sex cells/gametes) 2. Diploid (2n) = cells that contain TWO SETS of chromosomes (somatic cells / body cells)

i.e. When a sperm cell (1n) and an egg cell (1n) combine, the new cell will be diploid (2n)

1. A picture of the chromosomes in a dividing cell 2. Used to examine an individual’s chromosomes Karyotype:

KaryotypeKaryotype Normal Male

KaryotypeKaryotype wise.berkeley.edu/student/topFrame.php?projectID=23132 Karyotype BEFORE Mitosis Karyotype AFTER Mitosis

Haploid cell Diploid cell

Remember: How many chromosomes do humans have?

The Cell Cycle: Interphase and Mitosis Mitosis is a process that helps organisms grow, develop, and heal. Mitosis refers to the division of “body cells.” Think My Toe

(AKA--Mitotic Phase)

Period of cell growth and development that precedes mitosis and follows CYTOKINESIS (cell splitting) Longest phase of the cell cycle INTERPHASE: Centrioles

1.G 1 = Growth 1—most cell growth (cell contents are duplicated) 2.S = Synthesis—DNA is duplicated 3.G 2 = Growth 2—cell grow a little to prepare for division and “double checks” for errors

1. PROPHASE: Chromatin condense and thicken – now called chromosome. (DUPLICATED) The nuclear envelope breaks down Centrioles move to opposite "poles“ (or ends) of the cell

2. METAPHASE: 1. The spindle fibers (centriole) fully develops 2. The duplicated chromosomes align at the metaphase plate (middle)

3. ANAPHASE: 1. Sister chromatids of the duplicated chromosomes separate and begin moving to opposite ends (poles) of the cell. 2. Spindle fibers lengthen and elongate the cell. 3. Each pole contains a complete set of chromosomes.

1.Nucleus begins to form at opposite poles. 2.The nuclear envelopes and nucleoli also reappear. 4. TELOPHASE:

CYTOKINESIS: = the division of the original cell's cytoplasm. (There are now two separate cells)

Animal Cell Cleavage furrow forms and pinches cell in half. Cytokinesis: Animal Cell vs. Plant cell

Plant Cell Cell plate forms to divide the cell.

CELL CYCLE 1. Interphase 2. Cell Division (Mitosis + Cytokinesis) MITOSIS 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase

Cell Cycle Regulation  Cell growth and division are carefully controlled.  Not all cells will go through the cell cycle at the same rate. Examples of cells rapidly dividing: Examples of cells NOT dividing often: RBC Muscle cells Skin cells /2009/05/red-blood-cells.bmp _Cancer_(Non-Meloma)/The_Basics/Epidermis-dermis.jpg Bone marrow Digestive tract cells cooper&part=A1967&rendertype=figure&id=A Nerve cells

Cell Cycle Regulation continued...  Cells that do not need to grow and divide can enter G 0 (resting) until they are needed.

Regulation  Cells have both internal and external regulators. Internal regulators—are called cyclin and they make sure the cell is ready at certain checkpoints... If not, the cycle stops (see diagram) Is the cell big enough? Has all of the DNA duplicated completely or properly? Is the cell big enough? Are all of the chromosomes attached to spindle fibers and properly aligned on the metaphase plate?

Density-dependent inhibition External regulators— are called growth factors. If cells are touching other cells = no growth If space with no neighboring cells = grow/divide Regulation continued...

What happens if cells LOSE the ability to CONTROL the cell cycle?

Cancer  Cancer = uncontrolled cell growth... cancer cells do NOT respond to regulator signals... results in masses of cells called tumors... cancer = a disease of the cell cycle

Cancer: Results in masses of cells called tumors – malignant vs. benign Metastasize = travel

MEIOSIS: GOING FROM DIPLOID TO HAPLOID Making Gametes: Egg and Sperm

CELL DIVISION WITH MEIOSIS Where do your genes come from?

The cell cycle remains the same except… G1 S G2 Division: meiosis & cytokinesis

VideoVideo: Amoeba Sisters Meiosis makes unique haploid cells. As you study meiosis focus on two things: How are we ‘mixing things up’ so that our offspring are unique? How are we moving and separating the chromosomes so that we end up with ½ the material?

Process of nuclear division that reduces the number of chromosomes in new cells to HALF the number in the original cell. Diploid  Haploid

Meiosis results in... Sex Cells a.Female gamete = egg cell b.Male gamete = sperm cell Images from: Sex Cells (Gametes) are Haploid: ½ the genetic information!

Cells undergo all the phases of interphase  Then they enter MEIOSIS which involves TWO distinct cell divisions Division 1 Division 2 Image from:

1. What happens during interphase? 2. Where in an organism’s body will cells carry out meiosis? Checkpoint:

1.Meiosis I a.Prophase I (crossing over) b.Metaphase I c.Anaphase I (homologous chromosomes separate) d.Telophase I and cytokinesis Before Meiosis I happens, the cell will go through interphase: G1, S, G2 (just like Mitosis)

Prophase I Prophase I is the longest and most complex phase. All of the events that occurred during prophase of mitosis occur + Homologous chromosomes come together to form a SYNAPSE (TETRAD). CROSSING-OVER occurs.

Portions of chromatids break off and attach to adjacent chromatids on the homologous chromosome This allows for more genetic variability! We don’t want everyone to look the same.  Occurs during Prophase I Crossing Over:

Metaphase I Homologous chromosomes line up randomly at the center of the cell. We call this independent assortment.

Instead of all the chromosomes lining up in Metaphase in a single-file line, they will pair up with their homologous partner Mitosis Meiosis

Metaphase I

SOCKS!!!!! Lets practice with homologous chromosomes

Anaphase I During anaphase the homologous chromosomes in the center of the cell divide.

Telophase I / Cytokinesis Telophase I two nuclei form (23 duplicated chromosomes in each) Cytokinesis occurs resulting in 2 haploid daughter cells.

Interphase Telophase I Anaphase I Metaphase I Prophase I Cytokinesis Images from:

Meiosis II Meiosis II comes directly after cytokinesis. No growth (interphase) takes place. Meiosis II is broken into 4 events: prophase II metaphase II anaphase II (sister chromatids separate) telophase II and cytokinesis ( 4 haploid cells) The steps of Meiosis II are identical to mitosis.

Prophase II Prophase II is the same as prophase in mitosis. Chromatin condenses into chromosomes Nuclear envelope breaks down

Metaphase II Metaphase II is the same as metaphase in mitosis. Duplicated chromosomes line up in the middle of the cell Spindle fibers from the centrioles attach to each sister chromatid

Anaphase II Anaphase II is the same as anaphase in mitosis. Sister chromatids separate.

Telophase II Telophase II is the same as telophase in mitosis. At the end of the second Cytokinesis in Meiosis there are 4 haploid cells Males: 4 sperm Females: 1 egg + 3 polar bodies

Coming from Meiosis I Prophase II Metaphase II Anaphase II Telophase II Cytokinesis Images from:

1. When did crossing over occur? 2. When do homologous chromosomes separate? 3. Why are sex cells haploid? 4. When do the sister chromatids separate? Checkpoint:

Image from: Meiosis I = separates homologous chromosomes Meiosis II = separates sister chromatids

Down Syndrome ( Trisomy 21 )

Non-disjunction: Klinefelters (XXY) and Turner Syndrome (X)

At the end of meiosis II four UNIQUE daughter cells are produced (4 haploid cells)