AP Bio Cell Cycle PDF

Preview

Summary

AP Bio Unit 2 Cell Cycle...

Description

Principles of Biology Unit 2: Cell Division The Cell Cycle Cell Cycle -The cell cycle is the event sequence during which a eukaryotic cell replicates DNA and divides. -Lengths of gap phases vary by the type of cell. -There are two main sections of the cell cycle, Interphase (split into three sections) and Mitotic Phase. -Interphase -First Gap (G1) -During this phase, the cell is carrying out its normal cellular functions, along with slight growth to prepare for cellular division. -DNA Synthesis (S) -The section of the cell cycle where DNA is synthesized and replicated for cell division. -Second Gap (G2) -During this phase, the cell is growing and making final preparations for cellular division. -Mitotic Phase -The Mitotic phase of the cell cycle involves a pair of related processes; mitosis and cytokinesis. -Mitosis is the division of the nucleus that results in two identical nuclei (assuming no errors). -Prophase -The chromosomes condense. -The spindle (a protein apparatus that is responsible for moving the chromosomes around the cell during mitosis) starts to form in the cytoplasm -Prometaphase -The nuclear envelope disappears. -The spindle will attach to the kinetochores (a protein structure found in the centromere of each sister chromatid) in the centromeres of the chromosomes. -Metaphase -Once the spindle is attached to the chromosomes, it will move the chromosomes into a line formation in the middle of the cell. -Anaphase

-The sister chromatids split (which then consider them chromosomes) towards opposite sides of the cell. -Telophase -The new nuclear envelopes will for around the chromosomes. -The spindle disappears. -The condensed chromosomes begin to decondense. -Cytokinesis is the division of the cytoplasm that results in two daughter cells (usually occurs in conjunction with mitosis, but not always). -Cytokinesis usually begins during anaphase of mitosis. The cell starts to elongate when the chromatids are separated and pulled toward opposite sides of the cell. -How the cell splits varies depending on what type of cell is splitting. -In animal cells, a set of proteins called the contractile ring will slide past each other and contract the equator of the animal cell. -Plant cells have cell walls that would split by contractile rings. So plant cells have to build a separate cell wall dividing the two new plant cells REVIEW: If a fruit fly zygote goes through mitosis four times but never undergoes cytokinesis, what do you predict will be the outcome? -We start with one nucleus. After mitosis, we have two nuclei. After the second mitosis, we have four nuclei. After the third mitosis, we have eight nuclei. After the fourth mitosis, we have sixteen nuclei. So one cell would contain sixteen nuclei. REVIEW: How many chromosomes does a cell with 78 chromosomes during the G1 phase of the cell cycle have during prometaphase of mitosis? -Since prometaphase of mitosis occurs after DNA synthesis, the number of chromatids will have doubled, but since two chromatids still count as one chromosome, you will still have 78 chromosomes. -Mitotic Functions -Mitosis and cytokinesis have major roles in growth in eukaryotic organisms. -Cell division is also used for regeneration and repair. -Reproduction (not always associated with mitosis).

KEY TERMS  Anaphase: stage of mitosis during which sister chromatids are separated from each other.  Cell cycle: ordered series of events involving cell growth and cell division that produces two new daughter cells.  Cell cycle checkpoint: mechanism that monitors the preparedness of a eukaryotic cell to advance through the various cell cycle stages.  Centromere: region at which sister chromatids are bound together; a constricted area in condensed chromosomes.  Chromatid: single DNA molecule of two molecules of duplicated DNA and associated proteins held together at the centromere.  Cleavage furrow: constriction formed by an actin ring during cytokinesis in animal cells that leads to cytoplasmic division.  Cytokinesis: division of the cytoplasm following mitosis that forms two daughter cells.  G1 phase (also, first gap): first phase of interphase centered on cell growth during mitosis.  G2 phase (also, second gap): third phase of interphase during which the cell undergoes final preparations for mitosis.  Interphase: period of the cell cycle leading up to mitosis; includes G1, S, and G2 phases (the interim period between two consecutive cell divisions.  Karyokinesis: another name for mitosis, a form of nuclear division.  Kinetochore: protein structure associated with the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase.  Metaphase: stage of mitosis during which chromosomes are aligned at the metaphase plate.  Metaphase plate: equatorial plane midway between the two poles of a cell where the chromosomes align during metaphase.  Mitosis (also, karyokinesis): period of the cell cycle during which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase  Mitotic phase: period of the cell cycle during which duplicated chromosomes are distributed into two nuclei and cytoplasmic contents are divided; includes karyokinesis (mitosis) and cytokinesis..  Mitotic spindle: apparatus composed of microtubules that orchestrates the movement of chromosomes during mitosis.  Prometaphase: stage of mitosis during which the nuclear membrane breaks down and mitotic spindle fibers attach to kinetochores.  Prophase: stage of mitosis during which chromosomes condense and the mitotic spindle begins to form.  S phase: second, or synthesis, stage of interphase during which DNA replication occurs.  Telophase: stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by a new nuclear envelope....