Cell Cycle Mitosis & Meiosis

IN Pg. 16 Using Page 207 List the phases of Mitosis in order.

Do it Now Pg. 16 Using Page 267 List the phases of Meiosis in order.

Title Page 17 – This must be done with colored pencil or Magic Marker not Ink Pen Title page Title is CELL CYCLE. Draw label and write down all captions on figure 8.10 pg. 205 Draw label and write down all captions on figure 8.11 & 8.12 pg. 206 Draw label and write down all captions on figure 8.13 pg. 207 Draw label and write down all captions on figure pg. 266 Draw label and write down all captions on figure pg. 267 Draw label and write down all captions on figure pg. 270.

In Pg. 18 Do not write this, this is in purple Do not write this, this is in purple: I am still grading your notebooks. Do all of the activities today on Loose leaf paper or page extenders, then staple, tape or glue it into your notebook. What does cell theory state? There are 3 parts. Pg. 172 in your book.

Do it now! Pg. 18 – loose leaf paper to save and add to notebook. What does diploid mean?

Notes Pg. 19 – put on loose leaf save and then put in notebook. These notes are Cornell Style. Question in Red, Answer in Blue ink, Black ink or Pencil. 5 sentence summary in Green. 100 points Title is: Cell Cycle and Mitosis – Division of Diploid cells. No you do not have to draw the pictures. Once again save these notes

The Cell Cycle and How Cells Divide

What are the Phases of the Cell Cycle? The cell cycle consists of – Interphase – normal cell activity – The mitotic phase – cell divsion INTERPHASE Growth G 1 (DNA synthesis) Growth G 2 Cell Divsion

What are the Functions of Cell Division? 20 µm 100 µm 200 µm (a) Reproduction. An amoeba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism (LM). (b) Growth and development. This micrograph shows a sand dollar embryo shortly after the fertilized egg divided, forming two cells (LM). (c) Tissue renewal. These dividing bone marrow cells (arrow) will give rise to new blood cells (LM).

What is Cell Division? An integral part of the cell cycle Results in genetically identical daughter cells Cells duplicate their genetic material – Before they divide, ensuring that each daughter cell receives an exact copy of the genetic material, DNA

What is DNA? Genetic information - genome Packaged into chromosomes 50 µm Figure 12.3

Why are DNA And Chromosomes important? An average eukaryotic cell has about 1,000 times more DNA then an average prokaryotic cell. The DNA in a eukaryotic cell is organized into several linear chromosomes, whose organization is much more complex than the single, circular DNA molecule in a prokaryotic cell

What are Chromosomes? All eukaryotic cells store genetic information in chromosomes. – Most eukaryotes have between 10 and 50 chromosomes in their body cells. – Human cells have 46 chromosomes. – 23 nearly-identical pairs

What is the Structure of Chromosomes? Chromosomes are composed of a complex of DNA and protein called chromatin that condenses during cell division DNA exists as a single, long, double-stranded fiber extending chromosome’s entire length. Each unduplicated chromosome contains one DNA molecule, which may be several inches long

 Every 200 nucleotide pairs, the DNA wraps twice around a group of 8 histone proteins to form a nucleosome.  Higher order coiling and supercoiling also help condense and package the chromatin inside the nucleus: Structure of Chromosomes

5 µm Pair of homologous chromosomes Centromere Sister chromatids What are Karyotypes? An ordered, visual representation of the chromosomes in a cell Chromosomes are photographed when they are highly condensed, then photos of the individual chromosomes are arranged in order of decreasing size: In humans each somatic cell has 46 chromosomes, made up of two sets, one set of chromosomes comes from each parent

What are Chromosomes? Non-homologous chromosomes – Look different – Control different traits Sex chromosomes – Are distinct from each other in their characteristics – Are represented as X and Y – Determine the sex of the individual, XX being female, XY being male In a diploid cell, the chromosomes occur in pairs. The 2 members of each pair are called homologous chromosomes or homologues.

What are Chromosomes? A diploid cell has two sets of each of its chromosomes A human has 46 chromosomes (2n = 46) In a cell in which DNA synthesis has occurred all the chromosomes are duplicated and thus each consists of two identical sister chromatids Maternal set of chromosomes (n = 3) Paternal set of chromosomes (n = 3) 2n = 6 Two sister chromatids of one replicated chromosome Two nonsister chromatids in a homologous pair Pair of homologous chromosomes (one from each set) Centromere

What are Homologues structures? Homologous chromosomes: Look the same Control the same traits May code for different forms of each trait Independent origin - each one was inherited from a different parent

What is Chromosome Duplication ? 0.5 µm Chromosome duplication (including DNA synthesis) Centromere Separation of sister chromatids Sister chromatids Centrometers Sister chromatids A eukaryotic cell has multiple chromosomes, one of which is represented here. Before duplication, each chromosome has a single DNA molecule. Once duplicated, a chromosome consists of two sister chromatids connected at the centromere. Each chromatid contains a copy of the DNA molecule. Mechanical processes separate the sister chromatids into two chromosomes and distribute them to two daughter cells. In preparation for cell division, DNA is replicated and the chromosomes condense Each duplicated chromosome has two sister chromatids, which separate during cell division

Because of duplication, each condensed chromosome consists of 2 identical chromatids joined by a centromere. Each duplicated chromosome contains 2 identical DNA molecules (unless a mutation occurred), one in each chromatid: Chromosome Duplication Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Two unduplicated chromosomes Centromere Sister chromatids Sister chromatids Duplication Non-sister chromatids Two duplicated chromosomes

What is the Structure of Chromosomes? The centromere is a constricted region of the chromosome containing a specific DNA sequence, to which is bound 2 discs of protein called kinetochores. Kinetochores serve as points of attachment for microtubules that move the chromosomes during cell division: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Metaphase chromosome Kinetochore microtubules Centromere region of chromosome Sister Chromatids

Structure of Chromosomes – Diploid - A cell possessing two copies of each chromosome (human body cells). Homologous chromosomes are made up of sister chromatids joined at the centromere. – Haploid - A cell possessing a single copy of each chromosome (human sex cells).

What are Phases of the Cell Cycle? Interphase – G 1 - primary growth – S - genome replicated – G 2 - secondary growth M - mitosis C - cytokinesis

What is Interphase? G 1 - Cells undergo majority of growth S - Each chromosome replicates (Synthesizes) to produce sister chromatids – Attached at centromere – Contains attachment site (kinetochore) G 2 - Chromosomes condense - Assemble machinery for division such as centrioles

What is Mitosis?  Some haploid & diploid cells divide by mitosis.  Each new cell receives one copy of every chromosome that was present in the original cell.  Produces 2 new cells that are both genetically identical to the original cell. DNA duplication during interphase Mitosis Diploid Cell

Mitotic Division of an Animal Cell G 2 OF INTERPHASEPROPHASE PROMETAPHASE Centrosomes (with centriole pairs) Chromatin (duplicated) Early mitotic spindle Aster Centromere Fragments of nuclear envelope Kinetochore Nucleolus Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Kinetochore microtubule Nonkinetochore microtubules

METAPHASEANAPHASETELOPHASE AND CYTOKINESIS Spindle Metaphase plate Nucleolus forming Cleavage furrow Nuclear envelope forming Centrosome at one spindle pole Daughter chromosomes Mitotic Division of an Animal Cell

What is the G 2 of Interphase? A nuclear envelope bounds the nucleus. The nucleus contains one or more nucleoli (singular, nucleolus). Two centrosomes have formed by replication of a single centrosome. In animal cells, each centrosome features two centrioles. Chromosomes, duplicated during S phase, cannot be seen individually because they have not yet condensed. The light micrographs show dividing lung cells from a newt, which has 22 chromosomes in its somatic cells (chromosomes appear blue, microtubules green, intermediate filaments red). For simplicity, the drawings show only four chromosomes. G 2 OF INTERPHASE Centrosomes (with centriole pairs) Chromatin (duplicated) Nucleolus Nuclear envelope Plasma membrane

What happens during Prophase? The chromatin fibers become more tightly coiled, condensing into discrete chromosomes observable with a light microscope. The nucleoli disappear. Each duplicated chromosome appears as two identical sister chromatids joined together. The mitotic spindle begins to form. It is composed of the centrosomes and the microtubules that extend from them. The radial arrays of shorter microtubules that extend from the centrosomes are called asters (“stars”). The centrosomes move away from each other, apparently propelled by the lengthening microtubules between them. PROPHASE Early mitotic spindle Aster Centromere Chromosome, consisting of two sister chromatids

What happens during Metaphase? Metaphase is the longest stage of mitosis, lasting about 20 minutes. The centrosomes are now at opposite ends of the cell. The chromosomes convene on the metaphase plate, an imaginary plane that is equidistant between the spindle’s two poles. The chromosomes’ centromeres lie on the metaphase plate. For each chromosome, the kinetochores of the sister chromatids are attached to kinetochore microtubules coming from opposite poles. The entire apparatus of microtubules is called the spindle because of its shape. METAPHASE Spindle Metaphase plate Centrosome at one spindle pole

What is The Mitotic Spindle The spindle includes the centrosomes, the spindle microtubules, and the asters The apparatus of microtubules controls chromosome movement during mitosis The centrosome replicates, forming two centrosomes that migrate to opposite ends of the cell Assembly of spindle microtubules begins in the centrosome, the microtubule organizing center An aster (a radial array of short microtubules) extends from each centrosome

Some spindle microtubules attach to the kinetochores of chromosomes and move the chromosomes to the metaphase plate In anaphase, sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell Microtubules Chromosomes Sister chromatids Aster Centrosome Metaphase plate Kineto- chores Kinetochore microtubules 0.5 µm Overlapping nonkinetochore microtubules 1 µm Centrosome The Mitotic Spindle

What happens during Anaphase? Anaphase is the shortest stage of mitosis, lasting only a few minutes. Anaphase begins when the two sister chromatids of each pair suddenly part. Each chromatid thus becomes a full- fledged chromosome. The two liberated chromosomes begin moving toward opposite ends of the cell, as their kinetochore microtubules shorten. Because these microtubules are attached at the centromere region, the chromosomes move centromere first (at about 1 µm/min). The cell elongates as the nonkinetochore microtubules lengthen. By the end of anaphase, the two ends of the cell have equivalent—and complete—collections of chromosomes. ANAPHASE Daughter chromosomes

What happens during Telophase? Two daughter nuclei begin to form in the cell. Nuclear envelopes arise from the fragments of the parent cell’s nuclear envelope and other portions of the endomembrane system. The chromosomes become less condensed. Mitosis, the division of one nucleus into two genetically identical nuclei, is now complete. TELOPHASE AND CYTOKINESIS Nucleolus forming Cleavage furrow Nuclear envelope forming

Mitosis in a plant cell 1 Prophase. The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is staring to from. Prometaphase. We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelop will fragment. Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate. Anaphase. The chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of cell as their kinetochore microtubles shorten. Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divided the cytoplasm in two, is growing toward the perimeter of the parent cell Nucleus Nucleolus Chromosome Chromatine condensing

What happens during Cytokinesis? Cleavage of cell into two halves – Animal cells  Constriction belt of actin filaments – Plant cells  Cell plate – Fungi and protists  Mitosis occurs within the nucleus

Cytokinesis In Animal And Plant Cells Daughter cells Cleavage furrow Contractile ring of microfilaments Daughter cells 100 µm 1 µm Vesicles forming cell plate Wall of patent cell Cell plate New cell wall (a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (SEM)

Do it again Pg. 18 How many stages are there in Mitosis?

Pg. 18 Out What is the longest stage of the cell cycle and why?

IN Pg. 20 loose leaf to be added to page 20 upon return of notebook Use loose leaf paper this is the last day to do this. Draw Prophase of Mitosis – use book or notes you have on loose leaf paper.

Do it Now Pg same as in Draw Metaphase of Mitosis.

Notes Loose leaf to be added into page 21 of notebook Cornell style notes. Added exercise – make your own questions for the slide titles I have not provided them so this time notes are worth 150 points.

Meiosis I : Separates Homologous Chromosomes Interphase Interphase – Each of the chromosomes replicate – The result is two genetically identical sister chromatids which remain attached at their centromeres

Prophase I This is a crucial phase for mitosis. This is a crucial phase for mitosis. During this phase each pair of chromatids don’t move to the equator alone, they match up with their homologous pair and fasten together (synapsis) in a group of four called a tetrad. During this phase each pair of chromatids don’t move to the equator alone, they match up with their homologous pair and fasten together (synapsis) in a group of four called a tetrad. Extremely IMPORTANT!!! It is during this phase that crossing over can occur. Extremely IMPORTANT!!! It is during this phase that crossing over can occur. Crossing Over is the exchange of segments during synapsis. Crossing Over is the exchange of segments during synapsis.

Metaphase I The chromosomes line up at the equator attached by their centromeres to spindle fibers from centrioles. The chromosomes line up at the equator attached by their centromeres to spindle fibers from centrioles. – Still in homologous pairs

Anaphase I The spindle guides the movement of the chromosomes toward the poles The spindle guides the movement of the chromosomes toward the poles – Sister chromatids remain attached – Move as a unit towards the same pole The homologous chromosome moves toward the opposite pole The homologous chromosome moves toward the opposite pole – Contrasts mitosis – chromosomes appear as individuals instead of pairs (meiosis)

Telophase I This is the end of the first meiotic cell division. This is the end of the first meiotic cell division. The cytoplasm divides, forming two new daughter cells. The cytoplasm divides, forming two new daughter cells. Each of the newly formed cells has half the number of the parent cell’s chromosomes, but each chromosome is already replicated ready for the second meiotic cell division Each of the newly formed cells has half the number of the parent cell’s chromosomes, but each chromosome is already replicated ready for the second meiotic cell division

Cytokinesis Occurs simultaneously with telophase I Occurs simultaneously with telophase I – Forms 2 daughter cells Plant cells – cell plate Plant cells – cell plate Animal cells – cleavage furrows Animal cells – cleavage furrows NO FURTHER REPLICATION OF GENETIC MATERIAL PRIOR TO THE SECOND DIVISION OF MEIOSIS NO FURTHER REPLICATION OF GENETIC MATERIAL PRIOR TO THE SECOND DIVISION OF MEIOSIS

Figure 13.7 The stages of meiotic cell division: Meiosis I

Meiosis II : Separates sister chromatids Proceeds similar to mitosis Proceeds similar to mitosis THERE IS NO INTERPHASE II ! THERE IS NO INTERPHASE II !

Prophase II Each of the daughter cells forms a spindle, and the double stranded chromosomes move toward the equator Each of the daughter cells forms a spindle, and the double stranded chromosomes move toward the equator

Metaphase II The chromosomes are positioned on the metaphase plate in a mitosis-like fashion The chromosomes are positioned on the metaphase plate in a mitosis-like fashion

Anaphase II The centromeres of sister chromatids finally separate The centromeres of sister chromatids finally separate The sister chromatids of each pair move toward opposite poles The sister chromatids of each pair move toward opposite poles – Now individual chromosomes

Telophase II and Cytokinesis Nuclei form at opposite poles of the cell and cytokinesis occurs Nuclei form at opposite poles of the cell and cytokinesis occurs After completion of cytokinesis there are four daughter cells After completion of cytokinesis there are four daughter cells – All are haploid (n)