Cell Division PowerPoint PDF

Mitosis and Meiosis Cell Growth and Division Copyright © Amy Brown Science Copyright © Amy Brown Science Limits to Cell Growth Why do cells divide? Instead of dividing, why don’t cells just grow larger and larger? There are two main reasons why cells divide rather than continuing to grow larger and...

Mitosis and Meiosis Cell Growth and Division Copyright © Amy Brown Science Copyright © Amy Brown Science Limits to Cell Growth Why do cells divide? Instead of dividing, why don’t cells just grow larger and larger? There are two main reasons why cells divide rather than continuing to grow larger and larger: The larger a cell becomes, the more … … demands the cell places on its DNA. If the cell grows too large, it will have trouble moving enough … … nutrients and wastes across the cell membrane. Problem #1: Our DNA has its limits! All of the __________ informa@on that a cell needs to function is DNA of the cell. stored in the ____ DNA is packaged into chromosomes ____________. A chromosome consists of one very long linear … … DNA molecule consisting of 1000's of genes. gene is the instructions Each _____ for making a particular protein that the cell needs. _______ Problem #1: Our DNA has its limits! The cell is constantly making copies of these genes and sending the copies (in the form of RNA) out to the ribosomes. When the cell is small, the information stored in the cellʼs DNA is adequate to meet the needs of the cell. As the cell grows too large, the cell”s DNA cannot meet the needs of the cell. The DNA cannot keep up with the demands of running a larger cell. © Amy Brown Science Problem #2: A Growing Cell Needs More Food ! food A cell must constantly take in … … food, oxygen, and water across the membrane. Waste products must constantly cross the membrane to ______________ leave the cell. _____ oxygen, and water A larger cell will require much more food, ____________________. much more waste A larger cell will generate ________________. Problem #2: A Growing Cell Needs More Food ! volume of the cell increases more As the cell grows, the _______ surface area of the ______________. cell membrane rapidly than the ___________ When the cell gets too large, the membrane surface area is not adequate to transport _____________________ ________ food, water, and waste products the large quantities of ____________________________ into and out of the cell. Surface Area to Volume Ratio in Cells The size of a cell is limited by its surface area-to-volume ratio. Example: Let’s consider three plant cells of different sizes. We will calculate the surface area to volume ratio in each cell. For simplicity, we will assume that each plant cell is a cube. Length: 1 cm Width: 1 cm Height: 1 cm Length: 2 cm Width: 2 cm Height: 2 cm Length: 3 cm Width: 3 cm Height: 3 cm Surface Area of Cell (length x width x 6) Volume of Cell (length x width x height) (1 cm) (1 cm) (6) (1 cm) (1 cm) (1 cm) Surface Area = 6 cm 2 2 (3 cm) (3 cm) (6) Surface Area = 54 cm 3 6/1=6:1 (2 cm) (2 cm) (2 cm) (2 cm) (2 cm) (6) Surface Area = 24 cm Volume = 1 cm Ratio of Surface Area to Volume Volume = 8 cm 3 (3 cm) (3 cm) (3 cm) 2 Volume = 27 cm 3 24 / 8 = 3 : 1 54 / 27 = 2 : 1 Surface Area to Volume Ratio in Cells Length: 1 cm Width: 1 cm Height: 1 cm Length: 2 cm Width: 2 cm Height: 2 cm Length: 3 cm Width: 3 cm Height: 3 cm Surface Area of Cell (length x width x 6) Volume of Cell (length x width x height) (1 cm) (1 cm) (6) (1 cm) (1 cm) (1 cm) Surface Area = 6 cm 2 2 (3 cm) (3 cm) (6) Surface Area = 54 cm 3 6/1=6:1 (2 cm) (2 cm) (2 cm) (2 cm) (2 cm) (6) Surface Area = 24 cm Volume = 1 cm Ratio of Surface Area to Volume Volume = 8 cm 3 (3 cm) (3 cm) (3 cm) 2 Volume = 27 cm 3 24 / 8 = 3 : 1 54 / 27 = 2 : 1 Describe what happens to the surface area to volume ratio as the size of the cell increases. Answer: There is a decrease in the surface area to volume ratio of the cell as it increases in size. Surface Area to Volume Ratio in Cells Length: 1 cm Width: 1 cm Height: 1 cm Length: 2 cm Width: 2 cm Height: 2 cm Length: 3 cm Width: 3 cm Height: 3 cm Surface Area of Cell (length x width x 6) Volume of Cell (length x width x height) (1 cm) (1 cm) (6) (1 cm) (1 cm) (1 cm) Surface Area = 6 cm 2 (2 cm) (2 cm) (6) Surface Area = 24 cm (2 cm) (2 cm) (2 cm) 2 (3 cm) (3 cm) (6) Surface Area = 54 cm Volume = 1 cm 3 Volume = 8 cm 3 (3 cm) (3 cm) (3 cm) 2 Volume = 27 cm 3 Ratio of Surface Area to Volume 6/1=6:1 24 / 8 = 3 : 1 54 / 27 = 2 : 1 Which cell would most efficiently be able to move materials into and out of the cell? Explain. Answer: The smaller cell will be able to move materials more efficiently into and out of the cell. There is a larger surface area of cell membrane in comparison to the volume of the cell. The membrane will be better able to take in resources and get rid of the wastes in the smaller cell. Surface Area to Volume Ratio in Cells Length: 1 cm Width: 1 cm Height: 1 cm Length: 2 cm Width: 2 cm Height: 2 cm Length: 3 cm Width: 3 cm Height: 3 cm Surface Area of Cell (length x width x 6) Volume of Cell (length x width x height) (1 cm) (1 cm) (6) (1 cm) (1 cm) (1 cm) Surface Area = 6 cm 2 (2 cm) (2 cm) (6) Surface Area = 24 cm (2 cm) (2 cm) (2 cm) 2 (3 cm) (3 cm) (6) Surface Area = 54 cm Volume = 1 cm 3 Volume = 8 cm 3 (3 cm) (3 cm) (3 cm) 2 Volume = 27 cm 3 Ratio of Surface Area to Volume 6/1=6:1 24 / 8 = 3 : 1 54 / 27 = 2 : 1 Does a cell need a high or low surface area to volume ratio? Answer: High What must cells do before they grow too large? Before becoming too large, a growing cell divides into 2 cells. Cell Division Cell division is the process by which cellular material is divided between ____________________. two new daughter cells _______ mother cell divides to form two _____________. daughter cells One __________ identical to each other and to the The two daughter cells will be ________ mother cell. copy of all Before cell division begins, the cell makes a _____ chromosomes (DNA) of its __________________. Each daughter cell will get … … one complete set of chromosomes. half the size of the parent cell, but immediately Each daughter is ___________ growing begins ________. Each daughter cell has an … … increased surface area to volume ratio. Chromosomes are composed of DNA and proteins. The DNA contains the coded genetic information of the cell. Each cell must make copies of its chromosomes before cell division occurs. Each daughter cell will get … … a complete set of chromosomes. The cells of different organisms have a characteristic number of chromosomes per cell. Human cells contain 23 pairs or 46 chromosomes per cell. Fruit flies have only 8 chromosomes, while the Red King Crab has 208. Cell division occurs in two main stages: 1. Mitosis: The division of the nucleus 2. Cytokinesis: The division of the cytoplasm The chromosomes are not visible except during __________. cell division At the beginning of cell division, the chromosomes _________ condense into compact, visible structures that are easily seen with a microscope. Well before cell division takes place, each chromosome is replicated or copied. At the beginning of cell division, each chromosome consists of two identical “sister chromatids.” These ___________ chromatids are connected at an area called a ____________. centromere centromere chromatid chromatid Sister Chromatids The Cell Cycle The cell cycle is the … … series of events that cells go through as they grow and divide. The cell cycle is the life of the cell from the time it is first formed from a dividing parent cell until its own division into two cells. During the cell cycle, a cell … … grows, prepares for division, and divides to form two daughter cells. The Cell Cycle The cycle consists of five major phases: 1. G1 (first gap) 2. S (synthesis) G2 phase Mitosis Cytokinesis 3. G2 (second gap) 4. Mitosis - the division of the nucleus 5. Cytokinesis - the division of the cytoplasm Interphase S phase G1 phase (NOTE: G1, S, and G2 phases are collectively known as interphase.) Preparation for Cell Division Before a cell can begin _______ mitosis and divide, it must form _________ duplicates of its chromosomes and produce supply of organelles for a __________________ the two ________________. daughter cells These preparations occur during the G1, S, and G2 phases of the cell cycle. These three phases are collectively known as Interphase. Preparation for Cell Division G1 phase a. The cell increases in size. b. The enzymes, cytoplasmic organelles and other molecules double in number. S Phase a. Replication of DNA occurs. G2 Phase a. The cell assembles the special structures needed for cell division. When interphase (G1, S, G2) is complete, the cell is ready to begin the process of cell division. Preparation for Cell Division - Interphase Of the cell cycle, interphase accounts for 90% of the time. The _______ nucleus is well defined and bounded by nuclear membrane the ________________. Preparation for Cell Division - Interphase centrioles nuclear membrane chromosomes Outside of the nucleus are centrioles two _________. Their function is to organize ____________ microtubules into a _______. spindle The spindle will help separate sister chromatids during mitosis. The centrioles will begin to move to ________ opposite sides of the nucleus _______ as spindle microtubules grow out of them. (It should be noted that plant cells do not contain centrioles, but still organize microtubules to form a spindle.) Preparation for Cell Division - Interphase G1 phase is a period of intense biochemical activity. size The cell doubles in ____, and the enzymes, cytoplasmic organelles and other molecules double in number ________________. The chromosomes have duplicated during the _______ S phase __________ and they appear as a jumbled mass of fibers. They have not yet condensed. G2 Phase: The cell assembles the special structures needed for cell division. The events of mitosis are divided into four stages or phases: Prophase Metaphase Anaphase Four Phases of Mitosis Telophase and Cytokinesis Stages of Mitosis – Early Prophase Early Prophase: a. The chromosomes coil and thicken and become distinct from one another. The chromosomes are now visible. Spindle composed of microtubules Sister chromatids connected by centromeres Centrioles disappears b. The nucleolus __________. c. The chromosomes are doubled throughout their _______ length. chromatid d. Each ____ half of the double chromosome is a _________. e. The chromatids are connected by a centromere __________. f. The _________ centrioles separate and start moving to opposite ends of spindle made of ____________ microtubules begins to form. the cell. A _______ Stages of Mitosis – Late Prophase (Prometaphase) Centrioles Completed spindle composed of microtubules Fragmenting nuclear membrane Sister chromatids Centrioles Late Prophase (Prometaphase): microtubules invade the nuclear membrane fragments and the ____________ g. The __________________________ spindle is completely formed. nuclear area. The _______ h. The spindle is a structure that will help to separate the chromosomes. During prophase the pairs of chromatids become attached to the fibers of the spindle. centrioles have moved to the opposite poles, forming the spindle i. The _________ as they go. Stages of Mitosis – Metaphase Centrioles Sister chromatids Spindle Centrioles Metaphase a. The centrioles are now at opposite sides of the cell. b. The spindle fibers will ____________ push and pull the chromosomes. c. The chromosomes ______ line up at the ______ center of the cell. d. Each chromosome is connected to a spindle fiber at its centromere. Stages of Mitosis – Anaphase Microtubules shorten Sister chromatids separate and are pulled to opposite sides of the cell Anaphase chromatids are pulled to a. The centromeres divide, and the ___________________ opposite sides of the cell. shorten b. The microtubules begin to _______. chromatids apart to opposite sides of the cell. This pulls the ________________ c. By the end of anaphase, the two sides of the cell have equivalent and complete sets of chromosomes. __________________________ Stages of Mitosis – Telophase Nuclear membrane reforms Cleavage furrow Telophase a. Nuclear membrane begins to form. b. The spindle is disassembled ____________, and the nucleolus becomes visible in each _________ daughter cell. pinch in c. The cell begins to _______. cleavage furrow This is called the ______________. Practice Identifying the Phases of Mitosis “Real” cells viewed under a microscope look a bit different that the above drawings. See if you can identify each of the following phases. Anaphase Prophase Telophase Practice Identifying the Phases of Mitosis “Real” cells viewed under a microscope look a bit different that the above drawings. See if you can identify each of the following phases. Metaphase Metaphase Telophase At the end of mitosis, two nuclei have been formed. Each nucleus has an identical set of chromosomes. Cytokinesis is … … the division of the cytoplasm. Cytokinesis Cytokinesis usually occurs at the same time as telophase. animal cells, a ______________ cleavage furrow pinches the cell In ______ membrane inward until the cell is pinched into ________________. two separate cells Each new cell contains its own nucleus, cytoplasm, and organelles. In plants, it is not possible for the cell to pinch inward because of the rigid cell wall. C E L L P L AT E In plants, a cell plate forms midway between the two nuclei. The cell plate continues to form across the cell until two separate cells have been formed. Fun Fact: About two trillion cells are produced by an adult human body every day. That’s 25 million cells per second! The Importance of the Cell Division Process 1. Depending on the type of cell, mitosis may take from just a few minutes to several days. 2. One mother cell has divided to produce two daughter cells. 3. The two daughter cells are identical to each other and identical to the mother cell. Results of Mitosis In unicellular plants and animals, mitosis results in new offspring by asexual reproduction. Results of Mitosis In multicellular organisms, mitosis results in the growth and repair of the organism. Importance of Mitosis The two new cells are exact duplicates. Importance of Mitosis This process ensures that the new cells will be able to carry out the same functions as the mother cell. Regulation of the Cell Cycle The frequency of cell division varies with the type of cell. Skin cells, cells of the digestive tract, and cells in the bone marrow that produce blood cells divide frequently throughout our lives. Liver cells maintain the ability to divide but only _________ do so on ____________, rare occasion say to repair a wound. The most specialized cells, such as muscle cells and nerve cells, do not divide at all. Controls on Cell Division 1. When cells come into contact with other cells, they _______ not growing respond by ___________. injury like a cut in 2. When an _____ the skin occurs, the cells at the edge of the injury begin to ____________ divide rapidly to fill empty spaces. 3. When the healing process nears completion, the rate of cell division __________. slows down Cell Cycle Regulators There are many proteins found on the inside and the outside of the cell that regulate cell division. traffic signals These proteins act as “____________” during the cell cycle. These proteins can _____________ initiate or halt phases of the cell cycle. There are three main “checkpoints” during the cell cycle. Cell Cycle Regulators G2 checkpoint A “checkpoint” in the cell cycle is a control STOP point where “_____” G1 checkpoint and “___” GO signals regulate the cell cycle. Mitosis checkpoint The three major checkpoints are found in the … … G1, G2, and M phases. Cell Cycle Regulators G2 checkpoint Mitosis checkpoint The G1 Checkpoint: a. This checkpoint seems to be the most important. If the cell receives the “go” signal at the G1 checkpoint, it G1 checkpoint will usually complete the cell cycle and divide. b. If it does not receive the “go” signal at this point, it will exit the G0 cycle and go into a nondividing state called the G0 phase. c. Many cells of the human body are actually in the G0 phase. For example, mature nerve cells and muscle cells ___________ never divide G0 phase Other cells, such as liver cells, can and remain in the ________. be called back from the G0 phase and divide as needed. Cell Cycle Regulators G2 checkpoint Mitosis checkpoint G1 checkpoint G0 The G2 Checkpoint: a. At this point, DNA repair enzymes check the results of DNA replication. b. If this checkpoint is passed, proteins will signal the cell to begin mitosis _______. Mitosis Checkpoint: exit mitosis and a. If a cell passes this checkpoint, it will __________ enter the ________ G1 phase once again. Uncontrolled Cell Growth grow uncontrollably the 1. If the cells in a tissue _________________, consequences may be severe. 2. Cancer cells _____________ do not respond to the signals that regulate the growth of cells. Cancer cells divide uncontrollably and form masses of cells called tumors. These tumors can damage the surrounding healthy tissues. Uncontrolled Cell Growth 3. All cancers have one thing in common: The protein regulators that control the cell cycle have failed to do their job. Meiosis and Sexual Reproduction Asexual Reproduction In asexual reproduction, offspring are produced by only one parent. Each parent passes ALL of its genes to the offspring. Binary fission Budding Hydra Asexual Reproduction Release of millions of fungal spores Advantages of Asexual Reproduction a. It is faster. b. Large numbers of offspring are produced. c. The parent does not have to find a mate. Asexual Reproduction Disadvantage of Asexual Reproduction a. All of the offspring are ___________. exactly alike no variation in the offspring. There is ___________ b. The ability to _____ adapt to a changing environment is greatly reduced. Sexual Reproduction Sexual reproduction requires two parents. Each parent passes on HALF its genes to its offspring. Male and female parents are required. The male produces sperm, and the female produces eggs. Disadvantages: a. The parent must find a mate. b. Very few offspring are produced. c. It takes longer. Advantage of Sexual Reproduction: All of the offspring are different. Sexual reproduction always involves: Gametes: Sex cells Fertilization: Union of sperm and egg Zygote: A fertilized egg Cell Division and Chromosome Number If an organism is the result of sexual reproduction, it will have ______ two sets of chromosomes. ________ One set comes from the mother ______ and one set comes from the father ______. These two sets are called homologous chromosomes ________________________. two copies of each Homologous chromosomes are the __________ chromosome one coming from the female parent and one ____________, coming from the male parent. Cell Division and Chromosome Number For example: An adult fruit fly has 8 chromosomes. Four of these chromosomes come from the female parent, and four of the chromosomes come from the male parent. The two sets of chromosomes homologous to one are ___________ another. carry the same genes but they Homologous chromosomes ___________________, expressions of the genes. may have different ___________ Cell Division and Chromosome Number A cell that contains ________ both sets of homologous chromosomes diploid is said to be “______.” Diploid means that there are two of each kind of chromosome in each cell. The number of chromosomes in a diploid cell is represented by the symbol 2N. Cell Division and Chromosome Number In the fruit fly cell, 2N = 8 ______. “N” is the number of different chromosomes that an organism has. In humans, 2N = 46. Human cells contain 23 pairs of homologous chromosomes. Diploid cells contain two complete sets of chromosomes. Cell Division and Chromosome Number Mitosis produces identical daughter cells. If the mother cell is ______, diploid two identical ___________________ diploid daughter cells will be produced. Chromosome Number in Gametes gametes of sexually The ________ reproducing organisms contain only single set of chromosomes. a _________ Gametes are said to be … … “haploid” or 1N. Egg and sperm cells must half the number of have ______________ chromosomes so that when fertilization occurs, the __________ zygote will have the proper ______ diploid number _____________. 1N + 1N = 2N Chromosome Number in Gametes The ____ cells that produce eggs and the ____ cells that produce sperm, are ___________. diploid or 2N So how do the egg and sperm cells get to be 1N? MEIOSIS!! Meiosis is a process of _______________ reduction division in which the number of chromosomes per cell reduced by half is _____________ through the separation _________ of homologous chromosomes. Meiosis occurs only in the egg and sperm cells production of __________________. The purpose of meiosis is to ______ reduce the chromosome number in the _____________ egg and sperm by half. Meiosis, like mitosis, is preceded by the replication ________________________. of chromosomes Unlike mitosis, this replication is then followed by two divisions, meiosis I and meiosis II _____________________. diploid cell will In meiosis, one _____________ divide to produce four haploid gametes ___________________. Phases of Meiosis Interphase: meiosis I each chromosome is _________. replicated Prior to ________, It is similar to chromosome replication of mitosis. sister chromatids are held together by a __________. centromere Two identical _______________ Phases of Meiosis Prophase I: Chromosomes shorten and thicken. pairs with its corresponding Each chromosome _____ ______________________ homologous chromosome to form a ______. tetrad There are _______________________. four chromatids in a tetrad This pairing of homologous chromosomes does not occur in mitosis. Phases of Meiosis Metaphase I: Tetrads line up at the center of the cell ________________________________. Anaphase I: tetrads break apart and the pairs move to The _________________ opposite sides of the cell. ____________ Sister chromatids ______________ remain attached at their centromeres. Phases of Meiosis Telophase I and Cytokinesis: two cells The cell separates into ________. haploid (1N) daughter cells Meiosis I results in two _______________________. Each daughter cell has ____ half the number of chromosomes as the original cell. Sister chromatids ______________. remain attached **There is no replication of chromosomes by either cell before entering meiosis II. Phases of Meiosis **There is no replication of chromosomes by either cell before entering meiosis II. Prophase II: The pairs of sister chromatids start toward the center. _____________________________________________ Metaphase II: ________________________________________________ Pairs of sister chromatids line up at the center of the cell. Phases of Meiosis Anaphase II: The sister chromatids move to opposite sides of the cell. _______________________________________________ Telophase II and Cytokinesis: ________________________________________ Meiosis II results in four haploid daughter cells. Importance of Meiosis One (2N) cell has divided to produce four (1N) sex cells. Importance of Meiosis The chromosome number of the egg and sperm is reduced by half to ensure that the zygote will have the proper number of chromosomes. “Crossing Over” During Meiosis tetrad 1. During prophase I, each ________________ pair of chromatids lines up next to its homologue __________. 2. This pairing of homologous chromosomes produces _______. tetrads four chromatids 3. A tetrad consists of ______________. 4. It is possible for the chromatids within a homologous pair to _____ twist around one another. break off and attach to Portions of the chromatids may ________ adjacent chromatids. crossing over 5. This process is called “____________.” “Crossing Over” During Meiosis 6. “Crossing over” is the exchange of genetic information (genes) between segments of homologous chromosomes during meiosis. 7. The result is that the offspring will receive a new combination of genetic information. This leads to variation in the offspring. Variation leads to … … adaptation and change. These variations may cause some of the offspring to be better suited to their environment. If they are better suited for their environment, it is more likely that they will survive to reproductive age and pass these favorable variations on to their offspring. If the result of crossing over causes the offspring to be _________ less suited for its environment, it may __________. not survive Or, if the offspring does survive, it may not be reproductively competitive _______________________. secure a mate This means that it may not be able to ____________. These “___________” unfavorable genes are not likely to be passed on to the offspring. Crossing over leads to evolution. Gamete Formation Meiosis produces four haploid cells that are different. In males, meiosis results in four sperm cells. Gamete Formation In females, four cells are produced, but only one will become a functional egg cell. All of the cytoplasm and all of the organelles are put into one egg cell. The other three cells will never be functional. Comparison of Mitosis and Meiosis Mitosis occurs in all cells of the body except egg and sperm. Meiosis only occurs in the formation of egg and sperm. Mitosis Meiosis In meiosis, each diploid cell divides twice to produce a total of 4 cells. In mitosis each diploid cell divides once to form 2 cells. Mitosis Meiosis In meiosis, each of the four cells contains half the number of chromosomes as the parent cell. In mitosis, each new cell contains the same number of chromosomes as the original cell. Mitosis In mitosis, the homologous pairs do not come together to form tetrads. In meiosis, the homologous pairs do come together to form tetrads. While the chromosomes are in tetrads, crossing over may occur. There will be no crossing over in mitosis. Meiosis Mitosis Meiosis In meiosis, the four haploid cells contain different combinations of chromosomes from each other. In mitosis, the new cells contain identical copies. Created by Amy Brown Copyright © Amy Brown Science All rights reserved by author. This document is for your classroom use only. This document may not be electronically distributed or posted to a public web site, except for permitted use in password-protected Google Drive, Google Classroom, or Microsoft OneDrive. http://www.teacherspayteachers.com/Store/Amy-BrownScience ClipArt Credits: Studio Devanna, The Painted Crow, Sarah Pecorino Illustration, Tangstar Science, Deposit Photo, Adobe Photo