Ap Biology Reading Guide Chapter 12

Ap Biology Reading Guide Chapter 12 AP Biology Reading Guide Chapter 12 The Cell Cycle This reading guide will help you understand the key concepts in Chapter 12 of your AP Biology textbook which focuses on the cell cycle It will guide you through the important processes key terms and concepts that you should be familiar with for your exam I What is the cell cycle The cell cycle is the orderly sequence of events that takes place between the time a cell is created by the division of its parent cell and the time it completes its own division to form two new daughter cells Why is the cell cycle important The cell cycle is essential for the growth development and repair of organisms It ensures that each daughter cell receives a complete and accurate copy of the parent cells genetic material II Phases of the Cell Cycle Interphase G1 Phase First Gap The cell grows and synthesizes new proteins and organelles This phase is critical for the cell to reach the appropriate size and ensure it has enough resources to complete the rest of the cycle S Phase Synthesis The cell replicates its DNA ensuring that each daughter cell receives a complete copy of the genome DNA replication is a complex and tightly regulated process that involves the unwinding of the DNA double helix the synthesis of new DNA strands and the proofreading of the newly synthesized DNA to minimize errors G2 Phase Second Gap The cell continues to grow and produce proteins necessary for mitosis The cell also synthesizes microtubules which will be used to form the mitotic spindle M Phase Mitotic Phase Mitosis 2 The process of nuclear division where the replicated chromosomes are divided equally between the two daughter nuclei Mitosis can be further divided into four stages Prophase Chromosomes condense and become visible the nuclear envelope breaks down and the mitotic spindle begins to form Metaphase Chromosomes line up at the center of the cell metaphase plate attached to the spindle fibers Anaphase Sister chromatids separate and move to opposite poles of the cell driven by the shortening of the spindle fibers Telophase Chromosomes arrive at the poles the nuclear envelope reforms around each set of chromosomes and the chromosomes decondense Cytokinesis The division of the cytoplasm which occurs concurrently with telophase In animal cells cytokinesis involves the formation of a cleavage furrow a constriction of the cell membrane that pinches the cell in two In plant cells cytokinesis involves the formation of a cell plate a new cell wall that grows between the two daughter cells III Regulation of the Cell Cycle Checkpoints Points in the cell cycle where the cell stops to monitor for any errors or problems There are three major checkpoints G1 Checkpoint Determines if the cell is large enough and has enough resources to proceed into S phase G2 Checkpoint Determines if the DNA has been replicated correctly and if the cell is large enough to proceed into M phase M Checkpoint Spindle Checkpoint Determines if all chromosomes are properly attached to the mitotic spindle before the sister chromatids are separated Cyclins and CDKs CyclinDependent Kinases Proteins that regulate the cell cycle Cyclins are regulatory proteins that fluctuate in concentration throughout the cell cycle CDKs are enzymes that are active only when bound to a specific cyclin Together cyclins and CDKs control the progression of the cell cycle by activating or inhibiting specific target proteins IV Growth Factors and Other Signals Growth Factors Signal molecules that stimulate cell division 3 DensityDependent Inhibition Cells stop dividing when they come into contact with other cells Anchorage Dependence Most cells require a surface to attach to in order to divide V Cell Cycle Disorders Cancer A disease caused by the uncontrolled growth and division of cells Mutations in genes that regulate the cell cycle Can lead to uncontrolled cell division and the development of cancer Protooncogenes Genes that stimulate normal cell growth and division Mutations in proto oncogenes can lead to the formation of oncogenes which can cause cancer Tumor Suppressor Genes Genes that inhibit cell growth and division Mutations in tumor suppressor genes can lead to uncontrolled cell division VI Meiosis What is meiosis A specialized type of cell division that produces gametes sperm and egg cells which have half the number of chromosomes as the parent cell Meiosis involves two rounds of division Meiosis I and Meiosis II to produce four daughter cells Key Events in Meiosis Meiosis I Prophase I Homologous chromosomes pair up and exchange genetic material through crossing over Metaphase I Homologous chromosome pairs line up at the metaphase plate Anaphase I Homologous chromosomes separate and move to opposite poles Telophase I Two daughter cells are formed each with half the number of chromosomes as the parent cell Meiosis II Similar to mitosis but each daughter cell from Meiosis I undergoes a second division separating the sister chromatids The result is four haploid daughter cells each with half the number of chromosomes as the original parent cell VII Importance of Meiosis Genetic Diversity Meiosis contributes to genetic diversity through Crossing over Exchange of genetic material between homologous chromosomes during Prophase I 4 Independent assortment Random alignment of homologous chromosome pairs at the metaphase plate during Metaphase I Gamete Production Meiosis ensures that each gamete receives only one copy of each chromosome ensuring proper chromosome number in the offspring VIII Conclusion Understanding the cell cycle is fundamental to understanding how life works at the cellular level The complex and tightly regulated processes of the cell cycle are essential for growth development and repair of organisms Understanding how the cell cycle is regulated and how it can go awry is crucial for understanding diseases such as cancer and for developing new treatments This reading guide has provided a foundation for understanding the key concepts in this important area of biology Be sure to review your textbook and class notes and practice applying these concepts to solve problems and answer questions