EXAM III STUDY GUIDE
EXAM III STUDY GUIDE HORT 1001
U of M
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Date Created: 11/26/15
EXAM III STUDY GUIDE: LECTURES 17-24 Lecture 17: Mitosis Ploidy Haploid (n): found in gamete cells Diploid (2n): found in zygote cells (1 set from male plant, 1 set from female) Triploid (3n): results from double fertilization found in endosperm cells (two from female’s polar nuclei, one from male) o Most of the cells of flowering plants that we have studied so far are often somatic cells (diploid) o Each species of plant has a characteristic number of chromosomes o Homologs carry the genetic info that affects the same characteristic or function Synthesis o Replication occurs in this process o Two chromosomes that are exact copies are called sister chromatids and are attached at the centromere Stages of Mitosis o Interphase G1, S, G2 Chromosomes are relaxes and replicate (S) Sister chromatids are NOT homologs o Prophase Chromatin begins to coil and condense to form chromosomes Nuclear membrane disappears and chromosomes spread out Spindle apparatus begins to appear o Metaphase Spindle grows and forms attachments to the kinetochore Sister chromatids move to the metaphase plate Sister chromatids are in their most condensed state o Anaphase Sister chromatids begin to separate (one migrates to one pole, the other migrates to the opposite)> now are chromosomes Spindle fibers shorten Chromosomes carrying the DNA are divided precisely so that each of the resulting cells has exactly the same chromosomes that were in the mother cell prior to division o Telophase The nuclear membrane forms around the chromosomes in each of the daughter cells and cytokinesis occurs Chromosomes de-condense>relaxed chromatin o Three keys to understanding how you can get two cells from one: DNA is completely replicated during the S stage of Interphase As the cell prepares to divide, the DNA condenses The process is very organized Lecture 18: Grafts and Wounds Grafting o Creates a chimera o Involves a scion and a rootstock o In budding, the scion is a bud when usually during grafting the scion and rootstock are the same length o Reasons to graft: Creates unique, commercially desirable ornamentals Perpetuate desirable genotypes of plant types that are notoriously tough to root Changes varieties or cultivars Produce trees with specialized forms such as a weeping habit Increasing the growth rate of seedlings Repair damaged plants Take advantage of rootstock characteristics o Reasons against grafting: Requires experience in technique There must be a good reason to graft, and no easier/cheaper way to accomplish the same ends Wound Healing o What happens when you do a stem cutting Cells along the cut surface are sliced open and become necrotic tissue The surviving cells respond in two ways: Cells rapidly get rid of compounds to protect plant from water loss and invasion of diseases and insects (takes hours) Cells are stimulated to divide and produces a callus (takes years) o What happens when you do a graft Within a few days, cell division starts and a callus forms (originates from parenchyma cells) Callus from the rootstock and scion grow together to form a callus bridge Parenchyma cell sin the callus bridge differentiate into cambium cells (only ones that lie between the cambium of the rootstock and scion) Once these links are formed, the cambium beings to initiate new xylem and phloem Differentiation of the xylem and phloem is quicker where cambium layers are closely aligned o Five requirements for a successful graft: The rootstock and scion must be compatible The cambium layers of the stock and scion must be closely aligned The graft must be done at the appropriate time Grafts must be protected from drying The grafted plant must receive proper post-graft care Examples of grafting in food plants: Apple, grape, and vegetables o Apples Scion is chosen based on what type of apple Rootstock is chosen to obtain the mature height preferred in mature o Grape Scion is chosen to reproduce the fruit characteristics you desire Rootstock is chosen to manage soil types and root pests (helped protect against grape phylloxera- developed in Minnesota) o Vegetables Useful in resisting soil-borne diseases in greenhouse production by choosing a disease resistant vegetable rootstock Lecture 19: Plant Growths, Soils, and Fertility Soil Texture o Sand is the biggest particle (high amounts = gritty soil) Provides great drainage and aeration Poor at holding moisture and nutrients Least surface area o Silt is intermediate particle (high amounts = floury soil) Intermediate properties between sand and clay o Clay is smallest particle (high amounts = velvety soil) Holds onto water so much that sometime plants can’t get any for themselves Lots of surface area and holds nutrients well Tends to be fertile o Can look at the USDA Soil Texture Triangle in order to find out what type of soil you have based on percentage of particles o Minnesota State Soil=Loam soil found in south-central Minnesota (Lester Soil) Soil Structure o Refers to the way in which the soil particles and other materials like the organic matter in the soil bind together into aggregates o Sand, silt, clay, and organic material create a granular structure o Large holes in aggregate provide spaces for gasses and water to pass through while smaller holes hold water o Organic matter helps to build the aggregates by acting like a glue o Space between and within aggregates that provides aeration-porosity o Soil with granular aggregation that favors plant growth by holding water and nutrients, yet allows for drainage and gas exchanges is said to have good tilth o Can improve soil structure by: Increase the soil organic matter Reduce soil compaction o Reducing compaction promotes drainage, moisture retention, and gas exchange o Tillage exposes organic matter to oxygen, which breaks it down, and reduces tilth Soil Organic Matter o Refers to carbon-based material in the soil that was originally a living organism whether plant, animal, or microbe o Humus is sticky and helps bind soil particles together into aggregates Releases nitrogen and other nutrients that the plant can take up for its growth Holds nutrients in the soil through electrochemical charge o Organic matter is added to soil in several forms: Compost Raw organic matter Green manure Incorporating crop residues o Don’t add too much organic matter otherwise it can impact the soil negatively Organic Crop Production o Is a highly regulated enterprise that takes concerted management skill and focus o The management system starts with the land, addresses its preparation, the types of soil amendments that are allowed, the types of seeds that can be planted, and how the crop is harvested and stored o GMO (genetically modified organisms) crops are not allowed in certified organic crop production Containers and Raised Beds o Can’t use garden soil because it compacts too tightly in pots and has terrible drainage o Use a soilless mix o Fairly highly maintenance o Salad tables (image) Don’s Original Question o Fertilizer’s Analysis Numbers represent the % of the fertilizer that is Nitrogen, Phosphorus, and Potassium (N-P-K) Nitrogen=key element in protein Phosphorus=important component in energy transfer molecules like ATP Potassium=essential part of the mechanism for moving nutrients into and out of cells Lecture 20: Photosynthesis Photoautotrophs o Plants are self-nourishing o Organic molecules are compounds associated with living organisms that contain carbon atoms o The organic molecules that a plant produces must be: Storable within the plant Capable of being broken back down by the plant to yield energy for use in growth, maintenance, and producing other required organic molecules Reasonably compact so that enough energy can be stored for growth Transportable within the plant Stable and non-toxic to the plant o Photosynthesis is the process on which photoautotrophs rely to capture the light energy and to produce carbon based organic molecules Fixes carbon (fix=secure) o Carbon sequestrian example: planting trees that photosynthesize, fix carbon, and store the carbon-rich product as wood Characteristics of Light o Light travels in waves o Longest visible wavelength=red light, invisible=infrared radiation and radio waves o Shorter visible wavelength=blue light, invisible=UV light, microwaves o Light also has a particulate nature, those particles are called photons (provide energy that drives photosynthesis Equation that summarizes photosynthesis tells us that 12 molecules of water plus 6 molecules of carbon dioxide, in the presence of chlorophyll, accessory pigments and light produces 6 molecules of oxygen gas, returns molecules of water back to the cell and produces one molecule of a simple sugar like glucose or fructose Light Reaction o One reaction that makes up photosynthesis o Uses light energy to split water, which transforms from the sun into hydrogen ions and electrons o Two chlorophyll pigments for observing light: Chlorophyll a and Chlorophyll b o High level of absorption means that the chlorophyll molecule uses that wavelength of light o Antenna complex captures and routes the energy from sunlight down to a collector called a reaction center o The process of one pigment capturing the photon’s energy and passing that energy on to an adjacent pigment molecules is important in photosynthesis o This water splitting reaction is called the light reaction or light-independent reaction because it requires light o 12H2O -> 6O2 + 24e- + 24H+ Light Independent Reaction o Takes place in the stroma of the chloroplast o NADPH and ATP carry the energy from the light that was originally transformed into hydrogen ions and electrons through the splitting of water Enter a process is called the Calvin Cycle Requires help of Rubisco o Triose phosphate (G3P) moves out of chloroplast into the mesophyll cell’s cytoplasm where they combine to produce 6 carbon molecules glucose and fructose which combine to form sucrose o 24H+ + 24e- + 6CO2 -> C6H12O6 + 6H2O Photosynthesis Summary o Summary equation: o 12H2O + 6CO2 -> 6O2 + 6H2O + C6H12O6 o Image on the right shows what happens in a mesophyll cell o Blue=represents a palisade mesophyll cell in a leaf o Green rectangle=represents a chloroplast o Ovals=thylakoids o Black dots=represents the antenna complexes Cellulose and Starch o Translocation of sucrose through the phloem to the sink provides cells with a source of stored energy and also building blocks for organic molecules o Two useful compounds resulting from the production of long glucose chains: starch and cellulose A bond angle makes a huge difference between the two because starch can be digested but cellulose (structure support) cannot be digested Just to Review Again o In the light reaction, pigments in the thylakoid membrane capture energy from sunlight, o The energy is used to split water, which releases oxygen to the atmosphere. o The energy used to split water is transferred into electrons and hydrogen atoms, and eventually to ATP and NADPH. o In the light independent reaction, the ATP and NADPH power the Calvin cycle that captures carbon from atmospheric CO2 and incorporates it into simple sugar molecules. o These simple sugars can be translocated to sinks where they are used for energy, converted into energy storage compounds, or converted into structural molecules. Lecture 21: Alternation of Generations Generalized plant life cycle o Antheridia (male), archegonia (female) o Alternation of Generations will vary among plants for: The physical appearance of each stage such as size, form, and vigor The time spent in each stage The mechanics of gamete production and fusion o Key Concepts about Alternation of Generations: Sexual reproduction always includes meiosis and fusion/fertilization Asexual reproduction never includes either of these processes Plants with sexual reproduction always have Part of the life cycle where all cells are haploid Part of the life cycle where all cells are diploid The sporophyte generation is superseded by the gametophytic generations when spores are produced bu the sporophyte plant through the process of meiosis or meiotic cell division The gametophyte generation is superseded by the sporophytic generations when gametes formed from the gametophyte fuse to form the zygote First Example: Moss Second Example: Ferns Characteristic Moss Fern Angiosperm Dispersal agent water water wind, pollinators Seeds or not? not not seeds Male gamete type flagellated flagellated nonflagellated Dominant gametophyte sporophyte sporophyte generation Independent G=Independent;G=Independent; G=Dependent; gametophyte (G) or S=DependentS=Independent S=Independent sporophyte (S) Third Example: Flowering Plants Lecture 22: Meiosis Propagation and Natural Selection o Asexual reproduction is strictly mitosis No natural selection because progeny will mirror fitness of parents o Sexual reproduction Natural selection occurs so this means that the DNA of the most fit plants will be represented more frequently in the next generation of plant than the DNA of the least fit plants that may never even survive to reproduce and pass on their DNA o Sex generates variation (the fuel for the engine of the natural selection) Meiosis Mechanics o Starts with a diploid cell and results in four haploid cells that we call spores o Stags of Meiosis Prophase I Nuclear Membrane disintegrates and chromosomes have replicated In this stage the homologous chromosomes pair up and form structures called tetrads This process of paring promotes chiasma and crossing over between sister chromatids of homologous chromosomes which results in genetic variation This DOES NOT occur in mitosis Metaphase I Tetrads are lining up on the metaphase plate, ready to divide Anaphase I Tetrads divide and homologs go to opposite poles Sister chromatids stay intact and DO NOT DIVIDE YET Telophase I Nuclear membrane reappears to separate the products of the first division DNA relaxes but NO REPLICATION OCCURS Prophase II DNA condenses again so that we can see the chromosomes Metaphase II The chromosomes line up at the metaphase plate Anaphase II Centromeres split and sister chromatids are pulled to opposite poles Telophase II Nuclear membrane reforms, cytokinesis takes place o **The “II” stages of meiosis correspond with the stages of mitosis o Two divisions in Meiosis HOMOLOGS separate in Anaphase I CHROMATIDS separate in Anaphase II. Centromeres holding the chromatids DO split. How do we get genetic variation among gametes? o Each gamete ends up with one of the homologs of the pair, not both o Crossing over and exchanging DNA between homologous sister chromatids in Prophase I is another source variation in gametes What is crossing over? o In Prophase I = synapsis o Arms of sister chromatids overlap (chiasma) and exchange DNA (crossing over) In Summary: o Meiosis is a type of cell division that starts with a diploid, 2n cell o The process includes two chromosome divisions and produces four haploid, n cells o The haploid cells are genetically different from each other due to crossing over in Prophase I and independent assortment inAnaphase I o Homologs separate in Anaphase I while sister chromatids separate (the centromeres divide) in Anaphase II. Lecture 23: Gametogenesis Sporangia o Found in two places within the flower depending on if they are a male or female gametophyte In the anther = micro sporangium In the ovary = mega sporangium Microsporogenesis o KNOW HOW TO DRAW THIS: o Result of microsporogenesis is either a male gametophyte (2- celled pollen grain) or a 3-celled pollen grain with a vegetative (or tube) cell plus two sperm cells o Exine coat is made of protein and other compounds and forms a protective coat around the 3-celled macrogametophyte Megasporogenesis o KNOW HOW TO DRAW THIS: o Ovule wall is made up of integument tissue and from this is where the diploid megaspore mother cells form o Megaspore mother cell undergoes meiosis and produces four megaspores (three disintegrate) o The left over cell undergoes mitosis 3x to form 8 haploid cells (=female gametophyte) o Only 6 of the nuclei are surrounded by own cell membrane, the two remaining are surrounded by one cell membrane which become the polar nuclei and contribute two of the three nuclei to the endosperm tissue Fusion or Fertilization o The pollen tube is one long skinny cell with 2 or 3 nuclei o A generative nucleus undergoes mitosis in the pollen tube to form two sperm cells o Black dot in picture to the farthest right is a micropyle Double Fertilization Embryo Growth o Embryo development is started when the zygote divides mitotically to form an apical and basal cell o The basal cell goes through multiple mitotic divisions to form a suspensor (which anchors the apical cell to the nucellus tissue on the inner surface of the maturing ovule wall) o The apical cell divides mitotically to form the embryo o Lobes will become cotyledons and between these is the stem and shoot apical meristem, and @ the base near the suspensor is the root apical meristem Lecture 24: Inheritance of big differences Quantitative or Qualitative Differences? o Qualitative (color of lowers, height, etc.) is influenced by genes of parents o Quantitative (seed yield, # of chloroplasts) is influenced by the environment o Some of the base sequences in DNA are translated into structural and enzymatic proteins that then influence cell and plant growth (genes) o Result of sweet corn is due to one mutative gene Phonotype, Genotype, and Environment o Phenotype = Genotype + Environment o Genotype: At the gene’s locus will be one of the gene’s alleles o Phenotype is the sum of the genotypic and environmental effects o “Nature” = genotype, “Nurture” = environment o P= G + E o Behavior = Nature + Nurture o Genotype has a larger influence on phenotype than environment does when talking about inherited characteristics that result in large, qualitative differences (simple inheritance, major gene inheritance, qualitative inheritance) o Environment has a huge impact on phenotype when considering inherited characteristics that result in small, quantitative differences (complex inheritance, minor gene inheritance, quantitative inheritance) Inheritance of a qualitative trait o Gregor Johann Mendel studied inheritance among pea plants (self- pollinating) Developed fundamental principles of modern genetics He studied many qualitative traits like: Seed shape (smooth v wrinkled) Seed color (green v yellow) Flower color (purple v white) His experiments led him to develop a model where seed plumpness is controlled by one gene with 2 alleles of the genetic code for that gene Recessive alleles are only expressed if no dominant alleles are present Three different possible genotypes found: SS diploids that are smooth (homozygous dominant) Ss diploids that are smooth ss diploids that are wrinkled (homozygous recessive) The F1 plant will produce the same numbers of S and s > reflects process of meiosis Use a Punnett Square!! Simultaneous inheritance of two qualitative traits o Seed color is controlled by one gene with two alleles: YY diploids are yellow Yy diploids are yellow yy diploids are green o Seed color and seed plumpness are two different types of chromosomes o SSYY x ssyy = SsYy Double heterozygote (smooth, yellow seeds) o If the SsYy F1 progeny self-pollinated: At prophase I, the chromosomes would replicate and show sister chromatids At Metaphase I, homologs have synapsed and line up on the metaphase plate Two ways the alleles could line up: o Both dominant gene homologs are on the same side o Dominant homolog for one gene could line up with the recessive homolog for the other gene The way the homologs line up affect how they are separated at Anaphase I, which will impact the type of spores produced in Telophase II In Telophase II, can result in dominant and recessive genes separated in other spores or one dominant w/ one recessive in each spore o “S-“ = “Ss” or “SS” because phenotype remains the same o Mendel’s First Law – The Law of Segregation During gamete formation each member of the allelic pair separates from the other member to form the genetic constitution of the gamete o The result of two genes on different chromosomes led to Mendel’s Second Law: the Law of Independent Assortment During gamete formation, the segregation of the alleles of one allelic pair is independent of the segregation of the alleles of another allelic pair Vocab for Exam III (Lectures 17-24) Lecture 17: Mitosis Ploidy: refers to the number of sets of homologous (identical) chromosomes in a cell Haploid: when cells contain two sets of chromosomes Diploid: when cells contain two sets of chromosomes Triploid: when cells contain three sets of chromosomes Somatic cells: diploid cells of flowering plants that we have studied so far (i.e. epidermis, cortex, vascular); each cell carries two sets of chromosomes Homologous chromosomes: the matching chromosomes from the two difference sets; carry the genetic information that affects the same characteristic or function Mitosis: the process that results in the formation of new cells Synthesis: replication process that causes each of the chromosomes to replicate Sister chromatids: two chromosomes that are exact copies Centromere: where the sister chromatids are connected in one spot Interphase (mitosis): chromosomes are relaxed and replicate; three stages: G1, S, G2 Prophase (mitosis): the chromatin begins to coil and condense to form chromosomes Spindles: microtubules associated with movement of the chromosomes during division Metaphase (mitosis): the spindle grows and forms attachments to sister chromatids which are in their most condensed phase Kinetochore: point of attachment between the spindles and the centromere (sister chromatids) Anaphase (mitosis): sister chromatids begin to migrate towards opposite poles; chromosomes carrying the DNA code are divided precisely Telophase (mitosis): the nuclear membrane forms around the chromosomes in each of the daughter cells Cytokinesis: process through which a cell plate forms between the two daughter cells and cell walls separate the newly formed cells Lecture 18: Grafts and Wounds Grafting: set of techniques for joining together two or more plant parts from different plant so that they appear to grow as one Chimera: two different plant genotypes are growing together in the same plant Scion: above-ground part of the plant Rootstock: a genotype he or she intends to use for the below ground portion Budding: the scion is simply a bud from a plant with the genotype that you want for the above ground part Callus bridge: forms when callus from the rootstock and scion grow together Lecture 19: Plant Growth, Soils, and Fertility Soil texture: refers to the relative proportion of sand, silt, and clay particles in the soil Soil structure: refers to the way in which the soil particles and other materials like the organic matter in the soil binds together into clumps Aggregates: clumps in the soil Granular structure: when sand, silt, clay, and organic matter interact to form small aggregates Aeration-porosity: how the soil has enough holes in the aggregates for gas exchange Organic matter: decaying bits of formerly living material Tilth: soil with granular aggregation that favors plant growth by holding water and nutrients, yet allows for drainage and gas exchange Soil organic matter: refers to carbon-based material in the soil that was originally a living organism whether plant, animal, or microbe Humus: material that is formed when soil organisms decompose the former living material and transform it Compost: leaves, weeds, grass clippings, and other organic materials are mixed together and occasionally turned to promote decomposition Raw organic matter: uncomposted organic material that is tilled in to the soil Green manure: when you grow a crop with the sole purpose of tilling the crop into the land to increase the organic matter GMO (genetically modified organisms): they contain one or more genes derived from other organisms Fertilizer’s analysis: a series of three numbers separated by dashes listed on a bag or container of fertilizer Lecture 20: Photosynthesis Autotrophs: self-nourishing Photoautotrophs: they use the energy from light to produce organic molecules with which they build their cells and store energy Organic molecules: compounds associated with living organisms that contain carbon atoms Photosynthesis: the process on which photoautotrophs rely to capture that light energy and to produce carbon based organic molecules Carbon sequestration: removal of carbon dioxide from the atmosphere (i.e. by planting trees) Carbon credits: where industries that discharge carbon dioxide into the atmosphere purchase credits from organizations whose activities sequester carbon Light Reaction: uses light energy to split water, which transforms the energy from the sun into hydrogen ions and electrons Light Independent Reaction: uses energy from LR to grab the carbon from carbon dioxide and use the carbon to build simple sugars Carotenoids: accessory pigments that assist chlorophyll in light capture and energy transfer, and also contribute to the regulation and moderation of excessive excitation of pigment molecules during intense sunlight Stroma: interior of the chloroplast Thylakoids: coin-like and located within the stroma Grana: stack of thylakoids Thylakoid membrane: membrane that surrounds thylakoids Antenna complex: an arrangement of green chlorophyll pigment embedded in the thylakoid membranes that captures and routes the energy from the sunlight down to a collector called a reaction center Resonance: a process in which released energy can be passed to another pigment molecule Calvin Cycle: where energy is used to fix carbon into a molecule abbreviated G3P Rubisco: the most abundant protein in leaves and catalyzes the Calvin cycle where carbon from the atmospheric carbon dioxide is incorporated into an organic molecule Source: regions of photosynthesis and sugar production Sinks: regions that do not support photosynthesis but still need organic molecules to survive Translocation: movement of solutes from source to sink through the phloem Starch: key energy storage compound in plant cells Cellulose: the main constituent of the cell wall and key to a plant’s structural integrity Lecture 21: Alternation of Generations Sporophyte: a plant that produces spores; diploid Meiosis: a type of cell division where one diploid cell divides to form four haploid cells Spore: a spore is the product of meiosis; marks the initiation of the gametophyte generation Gametophyte: a plant that produces gametes (like egg and sperm); haploid Gamete: produced from mitotic cell divisions of the gametophyte Zygote: the product of fusion between egg and sperm; diploid; marks initiation of the sporophyte generation Sporangia: specialized structures on the diploid plant where meiosis is going to occur Antheridia: specialized male structures Archegonia: specialized female structures Alternation of Generations: the alternation between sporophyte and gametophyte during the plant’s life cycle Flagellated sperm: sperm with whip-like appendages that give them motility in liquid Prothallus: the adult gametophyte Tube cell: directs the production of the pollen tube once the pollen grain lands on the stigma of a flower Generative cell: undergoes mitosis to form two sperm Lecture 22: Meiosis Genetic Variation: the fuel for the engine of natural selection Prophase I (Meiosis): in this stage, homologous chromosomes pair up and tetrads which promotes chiasma and crossing over between sister chromatids of homologous chromosomes Tetrads: groupings of four sister chromatids Chiasma: the point where sister chromatids of homologs lay over each other forming an “X” shape Crossing over: results in and exchange of DNA between homologs and is a contributor to genetic variation Metaphase I (Meiosis): tetrads line up on the metaphase plate, ready to divide Anaphase I (Meiosis): tetrads divide and homologs go to opposite poles Telophase I (Meiosis): the nuclear membrane reappears to separate the products of the first division Interphase I (Meiosis): DNA relaxes BUT DOES NOT REPLICATE Prophase II (Meiosis): DNA condenses again Metaphase II (Meiosis): the chromosomes line up at the metaphase plate Anaphase II (Meiosis): centromeres split and sister chromatids are pulled to opposite poles Telophase II (Meiosis): nuclear membrane reforms, cytokinesis takes place
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