Biology 171 Review Guide T2

Biology 171 Review Guide T2 - Biology 171 Review Guide Test...

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Biology 171 Review Guide Test # 2 Types of Cell Division: 1. Mitosis- produces two genetically identical daughter cells - Only in eukaryotes - Only in somatic cells 2. Binary Fission- produces two genetically identical cells - Only in prokaryotes 3. Meiosis- produces four daughter cells - Daughter cells are genetically different - Only in eukaryotes - Only in germ cells Key Roles of Mitosis: - Development and growth - Repair/tissue renewal - Asexual reproduction Ex: The same set of chromosomes (baring any mistakes in DNA replication) occurs in all somatic cells Steps of Mitosis: 1. Prior to Mitosis- chromosomes replicate 2. Interphase- after chromosome replication, each chromosome is composed of two sister chromatids - Centrosomes have replicated 3. Prophase- chromosomes condense, and mitotic spindle begins to form 4. Prometaphase- nuclear envelope breaks down - Spindle fibers contact chromosomes at kinetochore 5. Metaphase- chromosomes complete migration to the middle of the cell 6. Anaphase- sister chromatids separate - Chromosomes are pulled to opposite poles of the cell 7. Telophase- the nuclear envelope re-forms and the spindle apparatus disintegrates 8. Cytokinesis- cytoplasm is divided - Cell division of the two daughter cells form Steps in Bacterial Cell Division: Binary Fission 1. Chromosome attaches to plasma membrane 2. Chromosome replicates 3. Cell grows and ring of FtsZ ring protein forms 4. FtsZring constricts and the membrane and cell wall inford 5. Fission complete Asexual Reproduction: one parent produces genetically identical offspring
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Sexual Reproduction: two individuals combine genetic information and produce offspring that are genetically different In some species, both sexual and asexual reproduction takes place, at different times Advantages of Asexual Reproduction: - Don’t need a mate - Don’t need to expand time, energy, or resources to attract a mate - Fewer risks from predators - Fewer risks of sexually transmitted diseases (STD’s) - Leads to a faster population increase Disadvantages of Asexual Reproduction: - Little genetic variation for evolution to act upon - No way to get rid of deleterious mutations The majority of animal and plant species reproduction is exclusively sexual (requires meiosis and fertilization) Meiosis: a process of two consecutive cell divisions which reduce parental chromosome number (by half) and produce four haploid daughter cells - Each daughter cell is genetically different from a parental cell - Meiosis only occurs in eukaryotes and is restricted to germ cells - Germ cells are located in the gonads (testes and ovaries) - Accurate for sperm formation; in some species, egg formation produces just one functional gamete and 2-3 polar bodies Sex produces genetic variation and genetically diverse offspring any be more likely to survive disease and parasites; therefore more likely to persist in changing environment, and also allows purging of bad mutations.
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