Unit C: Cells, Chromosomes and DNA PDF

Unit C: Cells, Chromosomes and DNA Chapter 17 Cell Division and Chapter 20 Molecular Genetics (DNA) Cell Division Metro Biology 30 Chapter 17 p. 556 - 595 The Cell cycle, Mitosis and Meiosis 17.1 p, 558-563 THE CELL CYCLE...

Unit C: Cells, Chromosomes and DNA Chapter 17 Cell Division and Chapter 20 Molecular Genetics (DNA) Cell Division Metro Biology 30 Chapter 17 p. 556 - 595 The Cell cycle, Mitosis and Meiosis 17.1 p, 558-563 THE CELL CYCLE 3 Trav is - Biology 30 Cell Div ision  Why divide? ❖Given that... ❖ all life depends on the ability to grow, maintain, repair, and reproduce ❖ new cells arise only from the division of other cells ❖ approx. 100 trillion body cells arise from 1 fertilized egg in a human... ❖ Cells need the ability to accurately reproduce their genetic and cellular material = the processes of cell division: mitosis and meiosis ❖ Mitosis ❖ growth, maintenance and repair of body [somatic] cells ❖ maintains the normal number of chromosomes ❖ considered asexual cellular division ❖ Meiosis ❖ creation of gametes [germ cells] for reproduction ❖ reduces the number of chromosomes by half ❖ considered sexual cellular division ❖ FYI: 150 billion cell divisions take place every day in your body Trav is - Biology 30 Cell Div ision 4  Cell Division A single set of Male Male chromosomes Many adult Sperm embryo mitosis Meiosis 1N A double set of 2N divisions 2N chromosomes Fertilization Several Many mitotic mitotic Somatic cell Gamete Zygote divisions divisions production production Adult 2N Embryo 2N 2N Somatic cell Somatic cell production production Female Female embryo Many adult Meiosis Egg mitosis 1N 2N divisions 2N Trav is - Biology 30 Cell Div ision 5 Genetic Material in Eukaryotes Genetic information is found in a cell’s DNA within the nucleus Chromatin uncondensed molecules of DNA (deoxyribonucleic acid) and proteins (histones) DNA is tightly wound around the histones packaged so that ~3 m of DNA can fit inside a nucleus that measures ~ 5 μm in diameter like stuffing a 150 km string into a lunchbox uncondensed = mass of long, intertwined strands of DNA Chromosomes distinct groupings of condensed chromatin condensed = DNA that is visible under a light microscope as distinct, separate chromosomes Coiling into compact structures allows the chromatids to separate without tangling during cell division. Trav is - Biology 30 Cell Div ision 6  Chromatin vs. Chromosomes DNA is super-coiled inside the nucleus to form a condensed molecule that varies depending on where the cell is in its cycle ▪ Chromatin (interphase)- uncondensed mass ▪ Chromosomes (mitosis) – condensed into distinct, visible chromosomes FYI: The nucleosome: is the basic structural unit in chromatin, 7 consists of DNA coiled around 8 histone proteins Trav is - Biology 30 Cell Div ision c i h n r t e o r m p a h t a i s n e c h m r i o m t a o s s o i m s e s 8 Trav is - Biology 30 Cell Div ision Chromosome structure When a chromosome is replicated, each copy is known as a chromatid or sister chromatid they are held together by the centromere each chromatid is identical to it’s sister chromatid Interphase Replicated chromosome chromosome prepared for cell division Centromere This chromosome would not be visible as a coiled up structure, but unwound as a region of dense Sister Sister chromatin in the nucleus Chromatid Chromatid (as in the TEM of the nucleus above) Trav is - Biology 30 Cell Div ision 9 Centromeres and Kinetochores Proteins form a constriction point or centromere at a predictable location on each chromosome FYI: The kinetochore acts as a “docking site” on the centromere and links chromosomes to microtubules of the mitotic spindle Image of a human cell: microtubules in green DNA or chromosomes in blue 10 Trav is - Biology 30 Cell Div isionkinetochores in pink  FYI: Chromosome Number Chromosome numbers Organisms Chromosome No. vary considerably among organisms. human 46 chimpanzee 48 The numbers may differ gorilla 48 markedly even between closely related species: cattle 60 cat 38 goldfish 94 Drosophila 8 honeybee 32 or 16 Hydra 32 cabbage 18 beans 22 orange 18, 27 or 36 garden pea 14 Trav is - Biology 30 Cell Div ision 11 Chromosome Number: Ploidy Ploidy: the number of individual chromosomes per cell varies from one species to another humans: 46 chromosomes... (2n) = 46 and (n) = 23 corn: 20 chromosomes... (2n) = 20 and (n) = 10 fruit flies: 8 chromosomes... (2n) = 8 and (n) = 4 haploid (n) the number of different chromosomes per cell [one set] for human cells the haploid number is 23 found in germ cells/gametes diploid (2n) from the Greek word meaning ‘double’ human body/somatic cells have 2 copies of each chromosome 2 sets: one set from dad and one set from mom 23 (n) + 23 (n) = 46 (2n) some plant species can be polyploid: triploid (3n), tetraploid (4n) and even octoploid (8n) polyploid plants are usually larger and have larger flowers and fruits 12 Trav is - Biology 30 Cell Div ision  Genes on Chromosomes Gene: section of DNA containing instructions to make a protein. Each gene is found at a particular location or locus. These genes may have different forms, or alleles. Example: gene= hair colour, allele (variation)= brown, black, red, blonde In humans one allele is from your mom, the other from your dad. https://www.youtube.com/watch?v=IePMXxQ- KWYhttps://www.youtube.com/watch?v=IePMXxQ-KWY 4:39 What is a Chromosome? Stated Clearly El FYI: only about Rh 2% of the human genome seems to be made up of sequences that AMY code for proteins or RNA. RB Most of our DNA Fy actually comes MN from viruses TYS CBD We have about ABO HEMA 30,000 genes NP Chromosome: 1 4 9 13 X No. of genes: 1270Trav is - Biology 30 Cell465 Div ision 499 195 773 13  The Cell Cycle - Interphase most (90%) of a somatic cell’s life is spent in interphase chromosomes are duplicated/doubled after S phase but still called chromosomes since the chromatids are clipped together with the centromere 14 Trav is - Biology 30 Cell Div ision Interphase cells Interphase …2 Gap 1 (G1) ▪ Cell growth ▪ G used to mean ‘Gap’ – early scientists could not identify any specific activities in this phase, now know what occurs – renamed ‘growth’ Synthesis (S phase) ▪ DNA replication + growth ▪ Duplicated chromosomes mean that the DNA content in the cell has doubled ▪ How many chromosomes would be present in a human cell after S phase? ___ 46 How many chromatids? ___92 Gap 2 (G2) ▪ Cell growth and preparation for mitosis 15 Trav is - Biology 30 Cell Div ision The Cell Cycle: Mitosis & Cytokenisis mitosis the M phase provides a complete copy of the genome to each daughter cell has 4 phases: prophase metaphase anaphase telophase cytokensis divides the cell (cytoplasm & organelles) into Cells that are not actively dividing are said to be in two Go. Some cells enter Go and never divide again – different in plants these cells are said to be terminally differentiated. and animals due Example: highly specialized nerve, heart muscle cells to cell wall 16 Trav is - Biology 30 Cell Div ision Microtubules form the Mitotic Spindle Microtubules are microscopic intracellular tubes that form the mitotic spindle that extends from both poles (bipolar) Microtubules are assembled during prophase, and disassembled during anaphase 17 Trav is - Biology 30 Cell Div ision FYI: Plant Toxins Interrupt Microtubules Colchicine Taxol Derived from the autumn Derived from the the crocus (Colchicinum western yew (Taxus autumnale) brevifolia) Binds to tubulin subunits; Prevents microtubules from causes existing microtubules forming spindles  prevents to fall apart and prevents cells from dividing new ones from forming Chemotherapy drug Do workbook page 2: Drug used to treat gout #1. A & B 18 Trav is - Biology 30 Cell Div ision  early prophase Phases of Mitosis Mitosis is divided into phases based on the arrangement of chromosomes and the appearance or disappearance of cell structures. The stages are continuous and can have a variety of names. 19 Trav is - Biology 30 Cell Div ision  Prophase Prophase (early): chromatin condenses to form distinct & visible chromosomes nucleoli disassemble nuclear membrane disappears centrioles separate and migrate to opposite poles of cell mitotic spindle forms Prophase (late): microtubules attach to the kinetochores of the sister chromatids on each side of the centromere which holds the two sister chromatids together microtubules begin to move the duplicated FYI: late prophase = prometaphase chromosomes into position 20 Trav is - Biology 30 Cell Div ision  Metaphase Metaphase: microtubules line up the duplicated chromosomes at the equator aka: metaphase or equatorial plate most easily recognized phase Trav is - Biology 30 Cell Div ision 21  Anaphase Anaphase: centromeres divide to separate sister chromatids are now referred to as chromosomes microtubules shorten: tubulin subunits are disassembled by enzymes sister chromatids are pulled toward opposite poles Early Anaphase Trav is - Biology 30 Cell Div ision 22  Telophase Telophase: chromosomes have been pulled to the polar regions of the cell new nuclear membranes form around chromosomes at either pole nucleoli reassemble chromosomes decondense or uncoil to form chromatin cell furrow begins to develop at equator Trav is - Biology 30 Cell Div ision 23  Cytokinesis Cytokenisis: cleavage furrow (in animal cells only) forms to pinch the cytoplasm in two cell furrow continues until two separate cells are created identical to each other identical to the parent cell daughter cells now enter G1 of interphase cleavage furrow Trav is - Biology 30 Cell Div ision 24  Cytokinesis Plant Cells Animal Cells Vesicles from Golgi migrate A cleavage furrow forms to to equator and fuse to form pinch the cell in two double layered cell plate Microfilaments form a ring Cell plates spread, cellulose inside membrane, then begin to shorten like a is laid down between drawstring to pull membrane membranes to form cell walls into center of cell Mitosis Song 2:10 25 Trav is - Biology 30 Cell Div ision How cytokinesis differs in animal and plant cells: 26 Trav is - Biology 30 Cell Div ision  Doc Cam Review: Mitosis Duplicated Chromosomes chromosomes Nucleoli disappear; Nuclear remain condense and envelope breaks down elongated shorten Centrioles begin to Microtubules Kinetochores Centrioles have also move apart; attach to align at cell’s been duplicated Spindle app. forms kinetochores of equator or Trav is - Biology 30 Cell Div ision sister chromatids metaphase 27plate  Free spindle One set of Cytoplasm divided fibers push chromosomes each; along equator by poles apart begin uncoiling cleavage furrow Chromatids Nuclear Each daughter Spindle become envelope gets 1 nucleus disappears; independent reforms & half of Nucleoli chromosomes cytoplasm reappear 28 Trav is - Biology 30 Cell Div ision For your reference: Mitosis The centriole, which The mitotic spindle forms to later forms the spindle, organize the chromosomes. is also replicated. The spindle consists of fibers Interphase Early Prophase Late Prophase made of microtubules and Nuclear proteins. Membrane Cell ent ers mit osis Nucleolus Chromosomes Metaphase DNA continues condensing continue to coil up DNA is replicated into chromosomes and the and appear as to form 2 nuclear membrane begins to double-chromatids chromatids dissolve Chromosomes line up at the equator Anaphase Two new nuclei form. The Division of the cytoplasm cell plate forms across the (cytokinesis) is complete. midline of the parent cell. The chromosomes The two daughter cells are This is where the new cell segregate, pulling now separate cells in their wall will form. the chromatids own right. apart Do workbook page 5 Cytokinesis Telophase Late Anaphase Trav is - Biology 30 Cell Div ision 29  KEY: Interphase & Mitosis Interphase: Prophase (late): Metaphase: chromatin (blue) chromatin condenses to microtubules line visible – thread-like form distinct chromosomes up the duplicated appearance nucleoli disassemble chromosomes at the nuclear membrane nuclear membrane equator intact disappears aka: metaphase nucleoli present centrioles divide and or equatorial plate 2 centrioles present migrate to opposite poles (animal cells only) of cell outside nucleus mitotic spindle (red) forms microtubules (red) & begins moving the in interphase duplicated chromosomes arrangement each sister chromatid has it’s own kinetochore 30 Trav is - Biology 30 Cell Div ision  KEY: Mitosis & Cytokenesis Anaphase: Telophase: Cytokenisis: centromeres divide chromosomes have cleavage furrow (in to separate sister been pulled to the animal cells only) forms chromatids polar regions of the to pinch the cytoplasm are now referred cell in two to as chromosomes new nuclear cell furrow continues microtubules membranes form until two separate cells shorten: around chromosomes are created tubulin subunits at either pole identical to each are disassembled nucleoli reassemble other by enzymes chromosomes identical to the sister chromatids decondense or uncoil parent cell are pulled toward to form chromatin daughter cells now opposite poles cell furrow begins to enter G1 of interphase develop at equator Trav is - Biology 30 Cell Div ision 31  Mitosis in Onion Cells If the cells of a growing root tip are examined, a proportion of them are in Prophase Late Prophase mitosis. Cells in different stages of division can be seen, but the majority of Telophase the cells are in interphase. Late anaphase This reflects the large proportion of the cell cycle Anaphase spent in interphase. Trav is - Biology 30 Cell Div ision Prometaphase 32  Mitosis Micrographs Cell division for somatic growth and repair. 1. Interphase 2. Prophase 3. Metaphase 6. Telophase 5. Late Anaphase 4. Anaphase Trav is - Biology 30 Cell Div ision 33  Plant Mitosis Plants have centrosomes (the organelle that assembles the microtubules into the spindle. Plants do not have centrioles nor do they form asters. Animal cells do. 34 Trav is - Biology 30 Cell Div ision  You Try: Onion Root Slides 1 2 5 6 3 4 7 8 1.Telophase 2.Anaphase 3.Metaphase 4.Interphase 5.Anaphase 6.Metaphase 7.Prophase 8.Prophase 35 Trav is - Biology 30 Cell Div ision  Key: 1. late Prophase/early Metaphase 2. Metaphase 3. Telophase 4. early Telophase 5. early Telophase 6. Metaphase 7. Prophase 8. Anaphase 9. late Anaphase 36 Trav is - Biology 30 Cell Div ision https://www.youtube.com/watch?v=ofjyw7ARP1chttps://www.youtube.com/watch?v=ofjyw7ARP1 c 5:30 Mitosis – Made super easy https://www.youtube.com/watch?v=DwAFZb8juMQ 3:38 Stages of Mitosis 37 Trav is - Biology 30 Cell Div ision Summary: https://www.youtube.com/watch?v=ofjyw7 ARP1chttps://www.youtube.com/watch?v =ofjyw7ARP1c 5:30 Mitosis – Made super easy https://www.youtube.com/watch ?v=DwAFZb8juMQ 3:38 Stages of Mitosis Do workbook page 3: #2. A, B, C, page 4: D & E and page 5: F 38 Trav is - Biology 30 Cell Div ision 17.2 p. 565 - 571 APPLICATIONS OF THE CELL CYCLE 39 Trav is - Biology 30 Cell Div ision  Applications of the Cell Cycle: Cloning Cloning occurs when identical offspring are produced from a single cell or tissue Cells that are used in cloning must be totipotent A totipotent cell is a cell that is able to become any cell in the body of an organism (they are undifferentiated) In mammals, cells are undifferentiated until the 8-cell stage of development (3 divisions) Trav is - Biology 30 Cell Div ision 40  Applications of the Cell Cycle: Cloning Process in which identical offspring are formed from a single cell or tissue in parent organism Asexual or nonsexual reproduction Clone examples: Hydra – budding (clone grows out of parent cell or organism) Strawberries reproduce by runners Aspen trees (trembling aspen) in Elk Island National Park Parthenogenesis: new individual grows from an unfertilized egg (not enough males around) Trav is - Biology 30 Cell Div ision 41  Twins – Natural Clones (monozygotic) Identical twins form when a cell breaks free from the undifferentiated embryo and develops on its own Identical twins are clones of each other – they share the same DNA Trav is - Biology 30 Cell Div ision 42  Fraternal Twins (dizygotic) Fraternal twins form when two eggs are fertilized and implant at the same time These twins may appear different because they do not have http://www.inkycircus.com identical DNA Trav is - Biology 30 Cell Div ision 43  Three Main Types of Cloning 1. Recombinant DNA Technology DNA cloning/gene cloning refers to the process of inserting foreign DNA into a bacterial plasmid (host cell) The foreign DNA is then transcribed and translated into protein product by the bacterial cell Example: Using E. coli to produce human insulin 2. Reproductive Cloning Used to generate an animal that has the same DNA as a previously existing animal The procedure for creating a reproductive clone is shown in textbook and on slide #60 (frog) Cc, the first cloned Trav is - Biology 30 Cell Div ision cat, and her clone 44 Three Main Types of Cloning...2 3. Therapeutic Cloning AKA embryo cloning refers to creating embryos for research purposes Stem cells are harvested from the embryos and used to study development Stem cells can also be used to grow new cells, study diseases, experiment with effectiveness of new medicines, as well as many other applications in science, medicine, and technology FYI: Creation of Clones – Plants & animals (read text p.567 – 568) 45 Trav is - Biology 30 Cell Div ision  Cloning mammal cells More difficult Cells tend to be more specialized Dolly lived 6.5 years Cells must be taken before 8 cell stage of development (totipotent) Social and moral consequences of cloning are debated: benefits to medical research and agriculture/impact on Dr. Ian Wilmut, Scotland society? Trav is - Biology 30 Cell Div ision 46 FYI: Cloning mammals with adult cells: Dolly the sheep clone born July 5/96 died Feb 14/03 of lung cancer (6 yr. old. Had 6 offspring 47 Trav is - Biology 30 Cell Div ision Regulation of the Cell Cycle Within the average human, about 150 million cellular divisions take place per day Generally, cells will only divide at the correct time Within a cell, protein interactions serve as “start” and “stop” signals for division As well, external factors such as particular hormones, nutrient levels, and contact with other cells can regulate division Trav is - Biology 30 Cell Div ision 48 Telomeres – chromosome cap Once a cell can no longer undergo mitosis it dies Normal cells pass through the cell cycle only a finite number of times (50 – 100x) Telomeres reduce in length each time a cell divides Length of telomere of a child is longer than that of a 70 yr. old Telomere length serves as a molecular ‘clock’ for cellular aging Dolly cloned from a 6 yr. old sheep – clock started there.Trav is - Biology 30 Cell Div ision 49  Cancer Cells cancer is uncontrolled cell growth and division Cells divide too quickly to differentiate & are nonfunctioning, immature cells Normally, cells communicate & divide only to replace damaged cells Figure 1. Some tumor cells emerge from the primary site into circulation and other organ sites, a process called metastasis. Early detection of metastasis is However, cancer cells divide even if the hallmark of future cancer detection and treatment. there are healthy cells around it never lose their ability to divide telomeres do not shorten Unusual number of chromosomes Lose attachment to neighboring cells Metastasize: enter blood stream and invade other parts of body tumor Trav is - Biology 30 Cell Div ision 50 Figure 12.16 Density-dependent inhibition of cell division. Normal cells have: Anchorage dependence Controlled mitosis rates Contact inhibition Differentiation Cancer cells have: No anchorage dependence Uncontrolled mitosis No contact inhibition No differentiation Abnormal nuclei Multi-layered growth produces tumors Ability to release molecules that initiate growth of blood vessels (angiogenesis) 51 Trav is - Biology 30 Cell Div ision  Telomerase: in normal/cancer cells Telomerase = enzyme that maintains telomere length Is inactive in most cells, therefore, cells have a finite number of cell cycles Telomerase is reactivated in cancer cells. This allows cancer cells to maintain telomere length and divide continuously Developing drugs to block telomerase action in and slow https://www.youtube.com/watch?v=U0fRAr- down cancer cells ZHCohttps://www.youtube.com/watch?v=U0fRAr-ZHCo Telomeres 1:10 Senescence = biological aging; losing the ability to divide & grow Trav is - Biology 30 Cell Div ision 52  FYI: Cancer Treatments Cancer treatment can involve one of three main options: 1. Chemotherapy – targets many quickly dividing cells 2. Surgery – try and remove all cancer cells in an area 3. Radiation Therapy – gamma or x – rays to destroy all cells in a specific area. https://www.youtube.com/watch?v=GhfrHjB X5eA Cancer, How Cancer Starts 3:57 https://www.youtube.com/watch?v=mnTQTjBZoAEhttps://www.youtube.com/watch?v= mnTQTjBZoAE 2:39 Cancer Stem cell theory Do workbook page 6: https://www.mayoclinic.org/diseases-conditions/cancer/multimedia/cancer/vid- #1. A 20084738https://w ww.mayoclinic.org/diseases-conditions/cancer/multimedia/cancer/vid-20084738 Metastasis 1:37 Trav is - Biology 30 Cell Div ision 53 17.3 p. 572 - 581 MEIOSIS 54 Trav is - Biology 30 Cell Div ision The Importance of Meiosis Many species have 2 types of cells: somatic (body) and gametes (sex cells) Somatic: non sex cells. Depending on the species, chromosomes are duplicated in pairs, triplets, etc. Humans – body cells are diploid Gametes: sex cells – egg, sperm. Each chromosome has only one copy = haploid. Humans have 22 autosome pairs (body) and a single pair of sex chromosomes: X or Y. XX = female, XY = male Paired chromosomes are homologous. Homologous = homologs = carry the same genes at the same location (locus/loci). Trav is - Biology 30 Cell Div ision 55 Homologous Chromosomes 2 doubled homologous chromosomes Doubled (during Has 4 S phase) 2 chromosomes (not doubled) chromatids = chromosome: Same gene order at same place tetrad 2 identical (loci) on the chromosome - this is 2 sister chromatids what makes them homologs. chromatids clipped together May carry different alleles which are with centromere (versions/variations) of gene identical and Called sister Ex. Flower colour = gene non-sister chromatids pink or red flower = allele chromatids which are not. Trav is - Biology 30 Cell Div ision 56 The Formation of Gametes: Meiosis Meiosis: the formation of gametes or sex cells The chromosome number is reduced by half Human cell = 46 chromosomes, after meiosis, gametes will have 23 chromosomes Meiosis occurs in germ cells of gonads (reproductive organs): Cells of ovaries Cells of testes Gametes formed: Ova (eggs) in females; sperm cells in males Are the only cells in the body not produced by mitosis Meiosis has 2 phases where cell division occurs but ONLY ONE DNA replication event. Trav is - Biology 30 Cell Div ision 57 Human Life cycle: 58 Trav is - Biology 30 Cell Div ision  Double division of Meiosis DNA replication 1st division of meiosis separates homologous pairs 2nd division of meiosis separates sister chromatids 59 Trav is - Biology 30 Cell Div ision Meiosis I This involves the four stages seen in mitosis, but with distinct differences: Prophase I - homologous replicated pairs line up side by side in a process called synapsis to form tetrads - chromatids within the tetrad intertwine and exchange segments of DNA (known as crossing-over) - this process allows a huge genetic variety to occur - sister chromatids are no longer identical to one another Trav is - Biology 30 Cell Div ision 60  61 Trav is - Biology 30 Cell Div ision  62 Trav is - Biology 30 Cell Div ision  Meiosis I cont… Metaphase I - homologous pairs that have exchanged genetic material (tetrads) line up along the equatorial plate. - spindle fibers are attached to kinetochores of each pair of homologues Anaphase I - homologs are separated as the microtubules disassemble, pulling one homologue to each pole - the tetrad splits into 2 bivalents - segregation – reduction division occurs: one member of each homologous pair will be found in each of the new cells - diploid mother cell becomes 2 haploid daughter cells - each chromosome remains doubled Trav is - Biology 30 Cell Div ision 63  Meiosis I cont… Telophase I -cytoplasm divides, forming 2 cells -nuclear membrane begins to reform -2 cells are not identical to each other nor to parent cell - Each daughter cell contains 1 member of chromosome pair = haploid - Homologous chromosomes are no longer identical Interkinesis (including cytokinesis) -follows telophase I -divides the cytoplasm and its contents -2 distinct haploid cells separate and prepare themselves for meiosis II 64 Trav is - Biology 30 Cell Div ision  Meiosis I cont… Meiosis I is also called the reduction division as the original diploid cell has been split into 2 haploid cells because the homologs were separated, even though the bivalents have not yet been divided. tetrad → bivalent = dyad remember : haploid = one set of each type of chromosome Trav is - Biology 30 Cell Div ision 65  66 Trav is - Biology 30 Cell Div ision Label the following diagram of Meiosis I: Do workbook page 9: #1. C 67 Trav is - Biology 30 Cell Div ision KEY: Label the following diagram of Meiosis I: 68 Trav is - Biology 30 Cell Div ision  Meiosis II Has no DNA replication. The process is identical to the rest of the mitotic phases. The bivalents are split into chromosomes. Humans: end result in females is one egg (other cells die off as polar bodies) and in males are 4 sperm (fig 9 p.578) Trav is - Biology 30 Cell Div ision 69  Meiosis II cont… Occurs at approximately same time in each of the haploid daughter cells No interphase (therefore no S phase) and no DNA replication because the haploid cells already contain replicated sister chromatids Prophase II - nuclear membrane dissolves; spindle reassembles and attaches to kinetochores Metaphase II - arrangement of chromosomes, each with 2 chromatids, along equatorial plate Guided by spindles, the sister chromatids line up single file at the equator Chromatids remain pinned together by centromere Trav is - Biology 30 Cell Div ision 70  Meiosis II cont… Anaphase II - the centromeres holding sister chromatids together divide - the spindle begins to disassemble, pulling sister chromatids to opposite poles Telophase II – 2nd division of cytoplasm is completed 4 haploid daughter cells are produced from each meiotic division 71 Trav is - Biology 30 Cell Div ision  72 Trav is - Biology 30 Cell Div ision Label the following diagram of Meiosis II: Do workbook page 9: #1. D 73 Trav is - Biology 30 Cell Div ision KEY: Label the following diagram of Meiosis II: 74 Trav is - Biology 30 Cell Div ision Summary: The Meiosis Square Dance (start at 6:22) 75 Trav is - Biology 30 Cell Div ision  Origins of Genetic Variation 1. The Independent Assortment of Chromosomes -The two alternative arrangements of two homologous chromosome pairs on the metaphase plate in MI illustrates the randomness of nature of lining up -The positioning of each homologous pair of chromosomes at MI determines which chromosomes will be packaged together in the haploid daughter cells Trav is - Biology 30 Cell Div ision 76  What are the chances that an identical egg or sperm cell are produced during meiosis? The formula to determine the possible number of combinations is 2n , where n = the haploid number of the organism = 223 = 8,388,608 This means that there are approximately 8 million possible combinations of maternal and paternal chromosomes in the resulting gametes. Origins of Genetic Variation…2 2. Crossing Over Crossovers can only occur between homologous chromosomes during synapsis very early in Prophase I of meiosis 78 Trav is - Biology 30 Cell Div ision Origins of Genetic Variation…3 3. Random Fertilization -The random nature of fertilization adds to genetic variation -Consider 8 x 106 possible chromosome combinations in the egg, multiplied by 8 x 106 possibilities in the sperm which equals 64 x 109 diploid combinations in the zygote -When you add in the variation from crossing over, this number increases substantially, making each offspring a unique individual Trav is - Biology 30 Cell Div ision 79 Sexual reproduction creates variability Sexual reproduction allows us to maintain both genetic similarity & differences. https://www.you tube.com/watch ?v=iR7YjDUcKh Michael Ehttps://www.yo utube.com/watc & Kirk h?v=iR7YjDUcK hE 4:18 McGraw Hill Douglas animation Baldwin brothers Do workbook page 7: #1. A and page 12: #4 Martin & Charlie Sheen, Emilio Estevez Trav is - Biology 30 Cell Div ision 80 KEY: 4. Meiosis: Counting Chromosomes Record the number being asked for in each phase: Interphase 1. Number of chromosomes before S phase ____46____ 2. Number of homologous pairs before S phase ____23____ 3. Number of sister chromatids before S phase ____ 0____ 4. Number of chromosomes after S phase ____46____ 5. Number of homologous pairs after S phase ____23____ 6. Number of sister chromatids after S phase ____92____ 7. Number of sister chromatids per chromosome _____2____ Prophase I 1. Number of chromosomes ____46____ 2. Number of sister chromatids ____92____ 3. Number of homologous pairs ____23____ 4. Number of sister chromatids per tetrad ____ 4____ 5. Number of chromosomes per tetrad ____ 2____ Anaphase 1. Number of chromosomes going to each pole ____23____ 2. Number of sister chromatids going to each pole ____46____ Telophase I 1. Number of cells formed ____2_____ 2. Number of chromosomes in each cell ____23____ 3. Number of sister chromatids in each cell ____46____ Meiosis I starts with one cell that contains ____46______ chromosomes and ends with two cells that each contain ____23_____ chromosomes. 81 Trav is - Biology 30 Cell Div ision KEY: 4. Meiosis: Counting Chromosomes Meiosis II 1. Number of sister chromatids in prophase II _____46____ 2. Number of chromosomes in prophase II _____23____ 3. Number of chromosomes at each pole in telophase _____23____ 4. Number of chromosomes in each cell at the end of M II _____23____ 5. Number of cells formed by the end of M II _____4_____ Meiosis II starts with two cells that each contain _____23_____ chromosomes and ends with four cells that each contain ____23______ chromosomes. 82 Trav is - Biology 30 Cell Div ision  Gametogenesis: Sperm & Egg Production in humans Equal division of cytoplasm creating 4 motile (light, fast) sperm Unequal division of cytoplasm creating 1 large, stationary egg = ovum needs fuel ootid Only 1 ovum (egg cell) is produced from meiosis 3 - die Trav is - Biology 30 Cell Div ision 83 Timing of meiosis for female gametogenesis 2 million primary oocytes at birth – no more are produced Just before ovulation At puberty Just after ovulation fertilization ovulated but waits for fertilization Within minutes of fertilization About 400 are used in meiosis finishes reproductive lifetime 84 Trav is - Biology 30 Cell Div ision Male gametogenesis Males can produce 1 billion sperm cells/day Primary spermatocyte begin dividing by mitosis at puberty – they replenish themselves Males produce sperm from puberty throughout lifetime 85 Trav is - Biology 30 Cell Div ision  SUMMARY OF GAMETOGENESIS Do workbook page 11: #3. A & B 86 Trav is - Biology 30 Cell Div ision  Mitosis vs Meiosis Review Why Two Types of Divisions? Mitosis Meiosis Nuclear division mechanism Nuclear division mechanism occurring in somatic cells of occurring in gonadal tissues of multicellular eukaryotes multicellular eukaryotes Purpose Purpose ▪ Production of genetically ▪ Production of gametes (animals) identical cells or spores (plants, fungi, and ▪ Allow growth protists) with genetic variability ▪ Replace dead or ageing ▪ Production of cells that allow for cells sexual reproduction to occur ▪ Repair damaged cells/tissues ▪ Method of asexual reproduction in plants, animals, fungi, and unicellular protists 87 Trav is - Biology 30 Cell Div ision  Mitosis vs. Meiosis Mitosis Meiosis 1 division 2 divisions daughter cells daughter cells genetically identical genetically to parent cell different from produces 2 cells parent 2n → 2n produces 4 cells produces cells for 2n → 1n growth & repair produces gamete no crossing over crossing over 88 Trav is - Biology 30 Cell Div ision KEY: Label the following diagram comparing Mitosis and Meiosis: 89 Trav is - Biology 30 Cell Div ision Comparison of Mitosis and Meiosis Do workbook page 10: #2. http://highered.mcgraw-hill.com/olc/dl/120074/bio17.swf A, B & C and page 8: B 90 Trav is - Biology 30 Cell Div ision Differences across Kingdoms Not all organisms use haploid & diploid stages in same way which stage is dominant (2n or n) differs by species but must still alternate between haploid & diploid have to for sexual reproduction and genetic variation Trav is - Biology 30 Cell Div ision 91  Life Cycle Diagrams Humans (animals) vs plants alternation of generations: Trav is - Biology 30 Cell Div ision 92 Plant alternation of generations Plants also form gametes by meiosis Pollen = male sex cell Egg cells = female And are stored in a variety of structures (pods, ovules, flowers) Contain a haploid chromosome number Fusion of male and female gametes restores diploid chromosome number 93 Trav is - Biology 30 Cell Div ision Plant alternation of generations 94 Trav is - Biology 30 Cell Div ision Plant alternation of generations 95 Trav is - Biology 30 Cell Div ision Plant alternation of generations 96 Trav is - Biology 30 Cell Div ision FYI only: Example: Mosses 97 Trav is - Biology 30 Cell Div ision FYI only: Example: Ferns 98 Trav is - Biology 30 Cell Div ision FYI only: Example: Gymnosperms i.e. Evergreens like Pine trees p. 580 99 Trav is - Biology 30 Cell Div ision FYI only: Example: Angiosperms i.e. flowering plants – most advanced ht t ps ://twitter.com/NatureI s_Lit/status/153661851 6383772672ht t ps ://t w it ter.com/NatureI s_Lit/status /1536618516383772672 t ime-laps e s trawberry 10 s Do workbook pages 13 - 16: #5 100 Cell division and life cycles A – D Trav is - Biology 30 Cell Div ision 17.4 p. 582 - 586 ABNORMAL MEIOSIS 101 Trav is - Biology 30 Cell Div ision  Nondisjunction The improper separation of chromatids in meiosis can lead to nondisjunction two homologous chromosomes move to the same pole (anaphase, meiosis I) Two sister chromatids do not separate (anaphase, Meiosis II) The result is that one daughter cell will have 22 chromosomes while the other will have 24 As a result, when the zygote forms, it will have either 45 or 47 chromosomes These cells with too much or too little genetic information cannot operate effectively Trav is - Biology 30 Cell Div ision 102 Non-disjunction: Cell Division Gone Wrong autosomes or sex Patient Diagnosis Chromosomal chromosomes do not Abnormality separate properly Down syndrome extra copy #21 One cell receives an extra Edward extra copy #18 chromosome, and one cell syndrome is missing a chromosome Trisomy 16 extra copy #16 Aneuploidy = cells with an abnormal chromosome # Patau syndrome extra copy #13 If a cell has three copies of Turner syndrome missing an X one type of chromosome, (XO) it is a trisomy condition Metafemale extra X (2n + 1) If a cell has only one copy Klinefelter XXY of a chromosome, it is a Jacob syndrome XYY monosomy condition 103 (2n – 1) Trav is - Biology 30 Cell Div ision KEY: Nondisjunction Trav is - Biology 30 Cell Div ision 104 Nondisjunction creates gametes with an abnormal number of chromosomes (aneuploidy) 105 Trav is - Biology 30 Cell Div ision  Trisomy & Monosomy Nondisjunctive disorders can be classified as trisomy or monosomy Trisomy: 3 copes of a chromosome Monosomy: one copy of a chromosome Note: Nondisjunction Disorders’ symptoms and statistics are not to be memorized. Trav is - Biology 30 Cell Div ision 106  FYI: Nondisjunctive Disorders 1. Down Syndrome Trisomy 21 - delays in the way a child develops, both mentally and physically. -1 in every 800 babies - issues: varying degrees of lack of mental acuity, heart defects, loss of hearing due to repeated childhood ear infections, kidney problems. Joey Moss, who was born with Down Syndrome, has worked as an assistant to the training staff of both the Edmonton Oilers and Edmonton Eskimos since the 1984 – 1985 season Trav is - Biology 30 Cell Div ision 107 2. Turner Syndrome (X_) Monosomy of the X chromosome Possible symptoms in young infants include: Swollen hands and feet Wide and webbed neck A combination of the following symptoms may be seen in older females: Broad, flat chest shaped like a shield Drooping eyelids Dry eyes Infertility No periods (absent menstruation) Short height 1 out of 3,000 live births Most are miscarried before 20th week of pregnancy Trav is - Biology 30 Cell Div ision 108 3. Klinefelter Syndrome Sex chromosome Trisomy: XXY As babies: many XXY males have weak muscles and reduced strength Puberty: often don’t make as much testosterone as other boys. This can lead to a taller, less muscular body, less facial and body hair, and broader hips than other boys. As teens, XXY males may have larger breasts, weaker bones, and a lower energy level than other boys. Adulthood: look similar to males without the condition, although they are often taller. They are also more likely than other men to have certain health problems, such as autoimmune disorders, breast cancer, vein diseases, osteoporosis, and tooth decay. XXY males can have normal sex lives, but they usually make little or no sperm – infertile. Leaning Issues: learning to talk late, trouble using language to express thoughts and needs, problems reading, and trouble processing what they hear. 1 out of every 1,000 males 109 Trav is - Biology 30 Cell Div ision  Karyotyping In a karyotype, a picture of the chromosomes is taken during metaphase (since chromosomes are in their most condensed form) The chromosomes are then aligned in pairs and counted It can be used to diagnose disorders due to nondisjunction. Trav is - Biology 30 Cell Div ision 110  Chromosome Features Chromosomes can be identified by noting: Banding patterns Position of the centromere Banding pattern Acrocentric Submetacentric Metacentric Presence of satellites or Subterminal Centromere position Length of the chromatids These features enable homologous pairs to be matched and therefore accurate karyotypes to be made. Chromosome length Satellite endings Trav is - Biology 30 Cell Div ision 111  Human Karyotypes Karyotypes display the chromosome contents of a cell, organized according to their number, size and type. 1 2 3 4 5 Normal somatic human cells have a karyotype with 46 chromosomes (in 6 7 8 9 10 11 12 23 pairs) comprising: 22 pairs of autosomes. 13 14 15 16 17 18 1 pair of sex chromosomes. These determine the sex of an individual: XX = female 19 20 21 22 Y X XY = male Sex chromosomes Trav is - Biology 30 Cell Div ision 112  Human Female Karyotype Every cell (except Human Female: 44 + XX egg cells) in a normal human female has: 44 autosomes 2 sex chromosomes Sex chromosomes: XX = female Trav is - Biology 30 Cell Div ision 113  Human Male Karyotype Every cell (except Human Male: 44 + XY sperm cells) in a normal human male has: 44 autosomes 2 sex chromosomes Sex chromosomes: XY = male Trav is - Biology 30 Cell Div ision 114  115 Trav is - Biology 30 Cell Div ision Trisomy 21 Karyotype: Do workbook page 17: #1 and #2 116 and page 17: Review A, B, C and D Trav is - Biology 30 Cell Div ision Karyotyping Internet Activity Go to: Learn.Genetics @ https://learn.genetics.Utah.edu In the Genetics box on the home page, click on ‘BASIC GENETICS’ Scroll down to ‘Make a Karyotype’ and try matching the chromosomes. When done, go to any other section you find interesting. Trav is - Biology 30 Cell Div ision 117 Mitosis/Meiosis Web Activities Go to: www.biology.Arizona.edu Scroll down to Cell Biology and click on the link. Select Cell Cycle and Mitosis and read the information, view the animation. Take the quiz (11 mc). At the end of the quiz, click on The End. Select the link Online Onion Root Tips. Read the information and follow through the assignment. Use the table below to fill in your data so that you can rank the phases from longest to shortest. Click on Cell Biology and scroll down to Meiosis. Read the information, view the animation, take the quiz. Trav is - Biology 30 Cell Div ision 118