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Hypothesis-Driven Science. As a formal process of inquiry, the scientific method consists of a series of steps. The key element of the scientific method is hypothesis-driven science. Revise and repeat. Observation. Question. Hypothesis. Prediction. Experiment. Figure UN1-4.
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Hypothesis-Driven Science As a formal process of inquiry, the scientificmethod consists of a series of steps. The key element of the scientific method is hypothesis-driven science. Revise and repeat Observation Question Hypothesis Prediction Experiment Figure UN1-4
Reporting the Results of Experiments A scientific research report is a form of communication in which the investigator succinctly presents and interprets data collected in an investigation. • Abstract • Introduction • Materials and Methods • Results • Discussion • Literature Cited
Introduction • General background information relevant to the topic • Information specific to your hypothesis • A short description of the hypothesis • A description of how you proposed to test the hypothesis • Predictions of expected supportive for falsifying results
Cellular Reproduction Cell division- A process in which a cell divides into 2 or more cells. Functions of cell division: *reproduction (at the cellular level and organismal level) *growth and development *repair Mitosis- The process of nuclear division that results in two daughter nuclei genetically identical to the parent nucleus.
Chromosome Structure ●Chromosome unduplicated vs. duplicated ●Centromere ● Sister Chromatids
Phases of Mitosis LM (b) (a) (c) (d) • Interphase B. Prophase • C. Metaphase D. Anaphase E. Telophase
Cellular Reproduction • In asexual reproduction: • Formation of new individuals from cell(s) of a single parent resulting in offspring that are genetically identical to the parent. FUNCTIONS OF CELL DIVISION Asexual Reproduction LM Sea stars African Violet Amoeba
Cellular Reproduction • Sexual reproduction requires fertilization by the fusion of gametes, producing offspring that are genetically distinct from both parents.
Meiosis Meiosis – A type of cell division in which one diploid parent cell (2n) produces four haploid (n) daughter cells. • Haploid – cell or organism that contains one complete set of chromosomes (n). • Diploid - cell or organism that contains two complete sets of chromosomes (2n).
Meiosis Homologous chromosomes separate. Chromosomes duplicate. Sister chromatids separate. Duplicated pair of homologous chromosomes Pair of homologous chromosomes in diploid parent cell Sister chromatids MEIOSIS II MEIOSIS I INTERPHASE BEFORE MEIOSIS
Meiosis MEIOSIS I: INTERPHASE PROPHASE I METAPHASE I ANAPHASE I Microtubules attached to chromosome Sister chromatids remain attached Centrosomes (with centriole pairs) Sites of crossing over Spindle Sister chromatids Nuclear envelope Centromere Pair of homologous chromosomes Chromatin Homologous chromosomes pair up and exchange segments. Pairs of homologous chromosomes split up. Pairs of homologous chromosomes line up. Chromosomes duplicate.
Meiosis MEIOSIS II: SISTER CHROMATIDS SEPARATE TELOPHASE II AND CYTOKINESIS TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II Cleavage furrow Sister chromatids separate Haploid daughter cells forming Two haploid cells form; chromosomes are still doubled. During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing single chromosomes.
Crossing over Prophase I of meiosis Duplicated pair of homologous chromosomes • In crossing over: • Homologous chromosomes exchange genetic information • Genetic recombination, • the production of gene combinations different from those carried by parental chromosomes, occurs Homologous chromatids exchange corresponding segments. Chiasma, site of crossing over Metaphase I Spindle microtubule Sister chromatids remain joined at their centromeres. Metaphase II Gametes Recombinant chromosomes combine genetic information from different parents. Recombinant chromosomes
Meiosis Cross over: How do we account for genetic variation? *Independent assortment *Crossing over *Random fertilization Independent Assortment:
Energy, Catalysis and Biosynthesis Complexity of metabolism Metabolism *catabolism *anabolism *potential energy
Enzymes • Metabolism is the total of all chemical reactions in an organism. • Most metabolic reactions require the assistance of enzymes, proteins that speed up chemical reactions.
Enzymes Induced Fit
Enzymes Physical and chemical properties affect enzyme activity: Substrate Active site *activators *cofactor Substrate Inhibitor *coenzyme Active site *inhibitors Substrate Active site Inhibitor