Chapter 9 Cellular Reproduction

9.1 Vocabulary Cell Cycle Interphase Mitosis Cytokinesis Chromosome Chromatin

Section 1 Cellular Growth Standards: 2.5, 2.7, 4.2 Objectives: Explain why cells are relatively small. Summarize the primary stages of the cell cycle. Describe the stages of interphase.

Cell Size Limitations Limiting factor of size: surface area volume As cell grows  ratio of SA to volume decreases

Cells are Better Being Small Small cells  more efficient with cellular movement, transportation (supplying nutrients and eliminating waste), communication, cellular functions. Most cells reach certain size  stop growing or divide.

Cell Cycle – Cell Cycle – process of cellular reproduction; growing and dividing in eukaryotic cells. 3 main stages: 1.Interphase  growth 2.Mitosis  nuclear division 3.Cytokinesis  cytoplasm division Each cycle produces two identical cells. Most animal cells complete cycle in one day.

Stage 1: Interphase Interphase – cell grows to maturity, carries out cellular functions, and replicates DNA. – Most time (90%) spent at this stage. – 3 substages: 1.G 1 (Gap 1) Phase – cell is growing and synthesizing proteins 2.S (Synthesis) Phase – DNA is replicated (2 full sets of DNA); chromosomes replicate and divide 3.G 2 (Gap 2) Phase – cell prepares for nuclear division (mitosis)

Interphase

Stage 2: Mitosis Mitosis – cell’s nucleus and nuclear material (DNA) divide. – 4 substages: 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase Section 2

Stage 3: Cytokinesis Cytokinesis – cytoplasm divides  2 new daughter cells produced. – Shortest stage Section 2 Animal Cell Plant Cell

Prokaryote/Eukaryote Division Prokaryotes  Binary Fission – Similar to the cell cycle except an entire organism is replicated. Eukaryotes  Cell Cycle

Cell Cycle

Chromosome Structure Chromosome – structure that contains genetic material and passed from generation to generation; one long thread of DNA tightly coiled. Chromatin – relaxed form of DNA in the cell’s nucleus; DNA and proteins.

Time 0 Time 20 min Time 40 minTime 60 min

9.2 Vocabulary Prophase Sister Chromatid Centromere Spindle Apparatus Metaphase Anaphase Telophase

Section 2 Mitosis and Cytokinesis Standards: 2.6 Objectives: Describe the events of each stage of mitosis. Explain the process of cytokinesis.

Interphase (G1, S, G2) 1

Chromosome Structure Sister Chromatids – structure that contains identical DNA copies; formed during DNA replication (Interphase  S); 1/2 a chromosome. Centromere – center of the chromosome where sister chromatids attach.

Stage 2: Mitosis Process that increases the number of cells. – Adds new cells as you age – Replaces older, damaged cells – 4 substages of Mitosis  PMAT 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase

Prophase 1 st stage of Mitosis which cell spends most time Chromatin tightens (condenses)  chromosome Chromosomes are single structures  X Nuclear membrane disappears Nucleolus disappears Centromere Chromosome Pair of Centrioles Aster

Prophase (cont’d) Spindle Apparatus – functions to move and organize chromosomes before cell division; composed of: 1.Centrioles migrate to poles (animal cells only) 2.Aster fibers (microtubules) extend from centrioles  star like appearance 3.Spindle fibers (microtubules) form in cytoplasm

Prophase (cont’d) Towards the end, spindle fibers attach to sister chromatids of each chromosome. – Ensures each new cell receives one complete copy of DNA.

Mitosis - Prophase 2

Metaphase 2 nd Stage of Mitosis; shortest Motor proteins pull sister chromatids along the spindle apparatus toward the center. – Chromosomes all lined up in middle (or equator)

Mitosis - Metaphase 3

Anaphase 3 rd Stage of Mitosis Microtubules of the spindle apparatus shorten  sister chromatids separate and are pulled apart. Towards the end, chromosomes at poles.

Mitosis - Anaphase 4

Telophase 4 th (& Last) Stage of Mitosis Chromosomes at poles  relax  chromatin (looks like spaghetti). Two nuclear membranes form and nucleoli reappear. Spindle apparatus breaks down.

Mitosis - Telophase 5

Stage 3: Cytokinesis Divide cytoplasm  two identical daughter cells. Animal Cells  microfilaments pinch the cytoplasm in half forming (“cleavage furrow”) Plant Cells  cell plate forms between the two nuclei  cell wall forms

Cytokinesis 6

9.3 Vocabulary Cancer Carcinogen Apoptosis Stem Cell

Section 3 Cell Cycle Regulation Standards: 2.2, 2.5, 2.7 Objectives: Explain how cancer relates to the cell cycle. Describe the role of apoptosis. Summarize the two types of stem cells and their potential uses.

Cell Cycle Control Cell cycle controlled by 2 substances: 1.Cyclins  proteins 2.Cyclin-Dependent Kinases (CDKs)  enzymes Control how many and when cell are produced. – Cyclins connect to CDKs  turns them “ON” – Control different activities at different stages.

Cell Cycle Control CDKs are always in the “off” position  cells cannot continue to grow or divide. Turned “on”  cell enters next stage of cycle. Cyclin/CDKs are checkpoints that monitor for errors and can STOP cycle if problems occur.

Cycle/CDKs Checkpoints Monitor Cell Cycle

Abnormal Cell Cycle If cyclin and/or CDK is damaged  cell cycle will occur abnormally producing too many cells too quickly  cancer. Cancer – uncontrolled growth and division of cells; failure in the regulation of the cell cycle.

Cancer Cancer is unregulated cell growth. Tumors – large masses of cells caused by cancer. – Dangerous  crowd out healthy tissues. – Take blood and nutrients away from other tissues/organs. Colon Cancer Breast Cancer

Tumors Malignant – tumors that grow and spread fast Benign – tumors that grow and spread slow Metastasis – cancer spreads to different types of tissue by means of the circulatory system.

Causes of Cancer Carcinogens – substances that are known to cause cancer; chemicals that mutate DNA. – Alcohol, smoking, asbestos, radiation Cancer Genes  mutations occurring in DNA.

Cancer Therapies (not cures) Surgery  tumors cut out Radiation  high frequency waves used to kill cancer cells but also kills healthy cells Chemotherapy  drugs that kill fast growing cells

Apoptosis Not every cell is destined to survive. Apoptosis – programmed cell death; suicide of a cell that recognizes it isn’t functioning properly  cell shrivels and dies. – Helps protect cells from replicating and passing on its mistakes and developing cancer.

Stem Cells One single fertilized egg (cell)  produces many different types of cells. Stem Cells – unspecialized cells that can develop into specialized cells under the right conditions. – Embryonic Stem Cells  mass of cells that accumulate after sperm fertilizes an egg. If not accumulated immediately, the (embryo) cells will start to specialize  ethical controversial. – Adult Stem Cells  found in various tissues and can differentiate into other specialized cells.

10.1 Vocabulary Gene Homologous Chromosome Gamete Haploid Fertilization Diploid Meiosis Crossing Over

Section 1 Meiosis Standards: 2.2, 2.5, 4.2, 4.5, 4.7, 5.2, 5.4 Objectives: Explain the reduction in chromosome number that occurs during meiosis. Recognize and summarize the stages of meiosis. Analyze the importance of meiosis in providing genetic variation.

Asexual Reproduction Asexual Reproduction  organisms makes a complete copy of itself through mitosis. – New cells are formed by dividing old cells = every cell has the same DNA – All chromosomes are inherited from a single parent  genetically identical to offspring – Occurs in all organisms Budding in Yeast

Sexual Reproduction Sexual Reproduction  DNA is combined from two different sources through meiosis. – ½ DNA from one parent and ½ DNA from the other parent – Accumulates beneficial mutations faster than asexual reproduction – Occurs in many organisms (humans, animals, plants, fungus)

DNA, Genes, & Chromosomes Characteristic (such as hair color, height, eye color, etc.)  called a trait. – Instructions for each trait is on the chromosomes – DNA on chromosomes is arranged in segments (genes) which control the production of proteins. Each chromosomes consists of thousands of genes  determines characteristics and functions of cell.

Human Body Cells 46 chromosomes arranged in 23 pairs – 23 chromosomes from each parent – Every cell in body contains a complete set of chromosomes. – Homologous Chromosomes – pair of chromosomes; one chromosome from each parent. Same length, same centromere position, same genes (may carry different traits)

46 Human Homologous Chromosomes

23 Human Nonhomologous Chromosomes

Maintaining Chromosome Number (n) Autosomes – chromosomes found in asexually reproducing cells. – Diploid – 2 copies of each chromosome (2n) Gametes – sex cells involved in reproduction that have ½ the number of chromosomes (23 total chromosomes) – Not in pairs; each carries different genetic info. – Haploid – 1 copy of each chromosome (n) Male Gamete = sperm Female Gamete = egg

Fertilization Fertilization – process by which one haploid gamete (n) combines with another haploid gamete (n) to form offspring. – During fertilization, each gamete gives 23 chromosomes to offspring – After fertilization, cell contains 2n chromosomes (23 pairs = 46 individual chromosomes)

How Are Gametes Formed? NOT through mitosis Gametes are formed from diploid cells that start with all 46 chromosomes called germ cells. – Germ cells go through a process called meiosis that will produce sex cells that are haploid with only 23 chromosomes Males  spermatogenesis  end of meiosis 4 sperms cells produced Females  oogenesis  end of meiosis 1 egg cell is produced

Meiosis Type of cell division that reduces the number of chromosomes by half  “reduction division”. Occurs in the reproductive structures to produce gametes. Sexual reproduction Occurs in two parts: – Meiosis I – Meiosis II

Interphase Carry out various metabolic processes: increase size, produce RNA, synthesize proteins, and replicate DNA. Interphase

Meiosis I Prophase I Nucleus disappears Replicated chromosomes become visible  each with two sister chromatids. Synapsis  process of 2 chromosomes pairing (tetrad) Prophase I

Meiosis I Prophase I (cont’d) Crossing Over  chromosomal segments are exchanged between a pair of homologous chromosomes  increases genetic variation. Centrioles move to opposite poles, spindle fibers form.

Meiosis I – Prophase I

Meiosis I Metaphase I Spindle fibers attach to centromeres of each homologous chromosome. Pairs of homologous chromosomes line up at the middle (equator) of the cell. Metaphase I

Meiosis I – Metaphase I

Meiosis I Anaphase I Homologous chromosomes separate and move to opposite poles. – Reduces chromosome number  each side will receive 23 chromosomes. Anaphase I

Meiosis I – Anaphase I

Meiosis I Telophase I Homologous chromosomes (consisting of two sister chromatids) reach the cell’s opposite poles. Chromosomes relax Spindles disappear Nuclei reappear. Telophase I

Meiosis I – Telophase I

Cytokinesis Cytoplasm divides forming two haploid cells. Plants  cell plate forms Animals  cleavage furrow

Cytokinesis (after Meiosis I)

At the End of Meiosis I Only halfway completed. Cell may undergo interphase but DNA is NOT replicated this time.

Meiosis II Prophase II Nucleus disappears Spindle apparatus reappears Chromosomes condense  each still containing two sister chromatids. Prophase II

Meiosis II – Prophase II

Meiosis II Metaphase II Spindle fibers attach to centromere and chromosomes RANDOMLY line up at the center of the cell. Metaphase II

Meiosis II – Metaphase II

Meiosis II Anaphase II Sister chromatids are separated at the centromere by the spindle fibers pulling opposite directions. Single chromosomes move to oppose poles. – Reduce chromosome number  each side will receive 23 chromosomes.

Meiosis II – Anaphase II

Meiosis II Telophase II Chromosomes reach opposite poles. Chromosomes relax Spindles disappear Nuclei reappear

Meiosis II – Telophase II

Cytokinesis Cytoplasm divides forming 4 haploid cells.

Cytokinesis (after Meiosis II)

At the End of Meiosis II In humans  each cell contains 23 chromosomes. Each cell has the potential of having completely unique combination of genes.