Cell Cycle and Mitosis

Cell Cycle and Mitosis Cell Division — process by which a cell divides into 2 new cells 2 Daughter Cells Parent Cell The original cell is called the parent cell; 2 new cells are called daughter cells 2 Daughter Cells Parent Cell

Why do cells need to divide? Living things grow by producing more cells, NOT because each cell increases in size Repair of damaged tissue If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell

Do you remember? DNA Nucleus Genetic Information 1) Which cell organelle controls all cell functions? 2) What does this cell organelle contain? 3) What do ALL cells need in order to have the directions/code to perform functions correctly? Nucleus Genetic Information DNA

DNA DNA is located in the nucleus and controls all cell activities including cell division Long and thread-like DNA in a non-dividing cell is called chromatin Doubled, coiled, short DNA in a dividing cell is called chromosome Consists of 2 parts: chromatid and centromere

Compare and Illustrate DNA DNA in NON-DIVIDING Cell DNA in a DIVIDING Cell

Coils up into chromosomes Chromatin to chromosomes illustration: Chromatin Coils up into chromosomes Duplicates itself Why does DNA need to change from chromatin to chromosome? More efficient division

2 identical “sister” chromatids attached at an area in the middle called a centromere When cells divide, “sister” chromatids separate and 1 goes to each new cell

Cell Cycle and Mitosis Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell Every organism has its own specific number of chromosomes Examples: Human = 46 chromosomes or 23 pairs Dog = 78 chromosomes or 39 pairs Goldfish = 94 chromosomes or 47 pairs Lettuce = 18 chromosomes or 9 pairs

All somatic (body) cells in an organism have the same kind and number of chromosomes. Examples: Human = 46 chromosomes Human skin cell = 46 chromosomes Human heart cell = 46 chromosomes Human muscle cell = 46 chromosomes Fruit fly = 8 chromosomes Fruit fly skin cell = 8 chromosomes Fruit fly heart cell = 8 chromosomes Fruit fly muscle cell = 8 chromosomes

Cell Cycle -- series of events cells go through as they grow and divide Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again

Cell Cycle Outline Interphase Mitosis Cytokinesis G1: Cell Grows S: DNA Replicates G2: Growth & prepares for division Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

Cell Cycle and Mitosis Interphase Prophase Metaphase Anaphase Get a friend and create a sentence to help you remember the order of the cell cycle and mitosis. Use the first letter of each term. Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

Interphase Interesting things happen! Cell preparing to divide Genetic material doubles Cells most of their time in Interphase 14

Mitosis Begins Prophase, Metaphase, Anaphase, Telephase Mitosis – division of the nucleus into 2 nuclei, each with the same number of chromosomes Mitosis occurs in all the somatic (body) cells Mitosis Begins Prophase, Metaphase, Anaphase, Telephase

Prophase Chromosome pair up! Chromosomes become visible Prophase Nuclear membrane disappears Spindle fibers form Prophase 16

Metaphase Chromosomes meet in the middle! Spindle Fibers connect to chromosomes Metaphase 17

Anaphase Chromosomes get pulled apart Spindle fibers pull chromosomes to opposite sides 18

Telophase Now there are two! Chromosomes uncoil Spindle fibers disappear Two nuclei are formed Telophase 19

Cytokinesis Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides In animal cells the cytoplasm pinches in In plant cells a cell plate forms After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities

Mitosis is a type of asexual reproduction. There are two types of reproduction: Asexual Reproduction Sexual Reproduction parent reproduces by itself offspring is genetically identical to “mamma” Offspring is genetically unique creates diversity within population

Asexual Reproduction Mitosis Binary Fission Budding Spores Regeneration Vegetative Propagation

1) Mitosis 2) Binary Fission a parent cell splits into 2 daughter cells of = size w/ prokaryotes produce 2 identical daughter cells with the same # of chromosomes as the parent cell. (identical)

3) Budding 4) Spores spores are surrounded by a tough coat to help them survive harsh conditions. .. Produced and released a new, duplicate organism forms at the side of the parent and enlarges until an individual is created.

6) Vegetative Propagation 5) Regeneration 6) Vegetative Propagation stolons growth of new tissues/organs to replace those injured or lost. Common in invertebrates, especially Asteroidea (Sea Stars) and Annelida (Worms). * In some multicellular plants * new plants develop from the roots, stems, or leaves of the parent.

Sexual Reproduction Meiosis Cell division that results in haploid gametes; used for sexual reproduction

Haploid? When a gamete (sperm or egg) of an organism has HALF of the full amount of chromosomes Hap Half Remember, human cells have 46 chromosomes? Then the haploid # is 23 Sperm Egg

Meiosis Meiosis I Meiosis II Occurs in the same four phases as mitosis but in two steps: Meiosis I and Meiosis II Meiosis I All chromosomes make copes of themselves This doubles the # of chromosomes in the cell Meiosis II Begins in same two cells created by Meiosis I Creates FOUR new haploid cells Occurs in a manner very similar to mitosis

Outline of Meiosis Meiosis I Meiosis II Prophase I Metaphase I Anaphase I Telophase I Meiosis II Prophase II Metaphase II Anaphase II Telophase II

Prophase I Homologous chromosomes from each parent pair up! They form two attached sets of chromatids called a tetrad There are MANY ways the chromatids can line up: this is one source of genetic variation. Homologous chromosomes: 1 from each parent carry genes that control the same inherited traits. 30

Metaphase I Each tetrad meets in the middle! Spindle fibers connect centromeres Crossing over of chromosomes may occur to provide additional genetic variation – 2nd source of genetic variation 31

Anaphase I Homologous chromosomes move to opposite ends Tetrads get pulled apart Homologous chromosomes move to opposite ends 32

Telophase I Cells may finish cytokinesis OR proceed immediately with Meiosis II 33

Prophase II Chromosomes did NOT replicate At this point, the cell is haploid because it no longer has one of every kind of chromosome that was in the original cell 34

Metaphase II Sister chromatids line up on individual spindle fibers 35

Anaphase II Sister chromatids are separated into each new cell Each new cell now has only HALF as many chromosomes as the parent cell in Prophase I 36

Telophase II Each of the four new cells completes reforming nuclei and cytokinesis separates the four new hapliod cells 37

How does meiosis lead to genetic variation? Look back at Prophase I & Metaphase I, what may lead to genetic variation? There are MANY ways the chromatids can line up Crossing over of chromosomes may occur What is another factor that could lead to genetic variation? Random combinations of sperm and eggs

Review! Interphase Interphase Prophase 1 Metaphase 1 Meiosis 1 Anaphase 1 Telophase 1

Prophase 2 Metaphase 2 Meiosis 2 Anaphase 2 Cytokinesis Cytokinesis

Note.. Male gametes Female gametes 4 haploid gametes … 4 sperm by way of spermatogenesis Female gametes 4 haploid gametes … 1 Ovum (egg) & 3 Polar Bodies by way of oogenesis

Sometimes cell division doesn’t go as planned…

Cell Division Regulation Internal and external factors regulate cell division. Cancer is the uncontrolled growth and division of cells. Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.

Cancer Benign – cancer cells typically remain clustered together Malignant – cancer cells can break away or metastasize cancer cell bloodstream normal cell metastasize Benign Malignant

Causes of Cancer Internal Factors External Factors Inheritance Mutations Skin Cancer External Factors Carcinogens are substances that are known to produce and promote the development of cancer. Radiation Chemical Viruses

Nondisjunction Mutations Improper separation of sister chromatids may result in a cell having one too many chromosomes (trisomy) or not having one of a certain chromosome (monosomy) Karyotype – a picture of an individual’s chromosomes so that the types of mutations might be seen

Trisomy 21 – Down Syndrome Trisomy 18 - Edward's Syndrome

Meiosis Square Dance