Cell Biology Ch 9.4

Mitosis is the process of cell division in which one cell nucleus divides into two nuclei. The primary purpose of mitosis is to ensure that each daughter cell receives an identical set of chromosomes. During mitosis, the duplicated chromosomes are separated and distributed equally between the two daughter cells. This ensures that each daughter cell has the same complement of chromosomes as the parent cell, maintaining the genetic stability and integrity of the organism.

The cell cycle consists of four main phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis). During the G1 phase, the cell grows and prepares for DNA replication. In the S phase, DNA replication occurs. The G2 phase is a period of further growth and preparation for cell division. Finally, the M phase involves the actual division of the cell into two daughter cells. The term "Go" is not part of the cell cycle and is not a recognized phase.

The S phase is responsible for the synthesis of DNA. During this phase of the cell cycle, the cell's DNA is replicated in order to prepare for cell division. This ensures that each daughter cell will receive an identical copy of the genetic material. The S phase is a crucial step in maintaining the integrity and stability of the genome.

G1, S, and G2 phases are collectively known as interphase. This is the phase in the cell cycle where the cell prepares for division by growing, replicating its DNA, and undergoing necessary metabolic activities. It is essentially the period between cell divisions and is crucial for the cell's overall growth and functioning. During interphase, the cell is not actively dividing, but rather carrying out various processes to ensure successful division in the future.

Cytokinesis refers to the process of dividing the cytoplasm during cell division, resulting in the formation of two separate daughter cells. This stage follows the separation of the duplicated genetic material in the nucleus during mitosis or meiosis. During cytokinesis, the cytoplasmic components, including organelles and cellular structures, are evenly distributed between the two new cells, ensuring that each daughter cell receives a complete set of cellular machinery. Therefore, cytokinesis accurately describes the division of the cytoplasm to produce two distinct daughter cells.

Cytokinins are a type of plant hormone that plays a crucial role in cell division and growth. They stimulate the process of cytokinesis, which is the division of the cytoplasm and the formation of two daughter cells during cell division. Therefore, the presence of cytokinins is what causes cytokinesis to occur.

DNA, short for deoxyribonucleic acid, is a molecule that contains the genetic instructions used in the development and functioning of all known living organisms. It serves as the genetic material in all living cells and is responsible for transmitting hereditary information from one generation to the next. DNA carries the instructions for building and maintaining an organism, including the traits and characteristics that make each individual unique. Therefore, describing DNA as "genetic material" accurately captures its essential role in storing and transmitting genetic information.

Checkpoints or restriction points are regulatory points in the cell cycle where the cell "checks" for DNA damage, proper replication, and other factors before proceeding to the next phase. These checkpoints occur in G1, G2, and M phases of the cell cycle. In G1 phase, the cell checks for DNA damage and nutrient availability. In G2 phase, the cell checks for DNA replication completion and DNA damage. In M phase, the cell checks for proper chromosome alignment before proceeding to cell division. Therefore, the correct answer is "All of the Above" as all three phases contain checkpoints.

During metaphase in mitosis, the chromosomes become highly compacted and align themselves along the equator of the cell. This alignment ensures that each daughter cell will receive the correct number of chromosomes during cell division. The highly compacted state of the chromosomes allows for easier separation and distribution of genetic material to the daughter cells.

During the S phase, chromosomes are replicated to form pairs of sister chromatids. This phase occurs in the interphase of the cell cycle, specifically before the cell enters the mitotic phase. In the S phase, DNA synthesis takes place, where each chromosome is duplicated to form two identical sister chromatids connected at the centromere. This replication ensures that each daughter cell receives a complete set of genetic material during cell division. Therefore, the correct answer is S,S Phase.

A protein kinase cascade refers to the sequential activation of several protein kinases in a row. This process involves the transfer of phosphate groups from one kinase to another, leading to the activation or regulation of downstream signaling pathways. The cascade allows for signal amplification and fine-tuning of cellular responses. It is a common mechanism used in various cellular processes, including cell growth, differentiation, and immune response.

Growth factors are a group of proteins that stimulate certain cells to grow and divide. They play a crucial role in regulating cell growth, proliferation, and differentiation. Growth factors bind to specific receptors on the surface of target cells, triggering a cascade of intracellular events that ultimately lead to cell division and growth. These factors are essential for normal development, tissue repair, and maintenance of homeostasis in the body.

The correct answer is cyclins and cyclin-dependent kinases. Cyclins are regulatory proteins that control the progression of the cell cycle by binding to and activating cyclin-dependent kinases (CDKs). CDKs are enzymes that phosphorylate target proteins, leading to the events required for cell cycle progression. Together, cyclins and CDKs form a complex that regulates the transitions between the different phases of the cell cycle.