Biology 1401 Chapter 10 How Cells Divide

Cell division is the process by which cells reproduce and create new cells. It is responsible for the growth and reproduction of cells. During cell division, the genetic material is replicated and distributed equally to the daughter cells. This allows for the growth of tissues and organs in multicellular organisms, as well as the reproduction of single-celled organisms. Therefore, growth and reproduction are maintained by cell division. The other options - death, metabolism, movement, and organization - are not directly maintained by cell division.

A eukaryotic cell with a single set of chromosomes is called haploid. In haploid cells, each chromosome is represented only once, meaning there is only one copy of each chromosome. This is in contrast to diploid cells, which have two sets of chromosomes, and polyploid cells, which have multiple sets of chromosomes. Tetraploid cells specifically refer to cells with four sets of chromosomes. Therefore, the correct answer is haploid.

The correct answer is S. The primary growth phase of a cell is the S phase. During this phase, the cell synthesizes DNA and replicates its chromosomes. This is an essential step in cell division, as it ensures that each new daughter cell receives an identical copy of the genetic material. The S phase is followed by the M phase, where the cell undergoes mitosis or cell division. The C phase is not a recognized phase in the cell cycle.

During metaphase, the chromosomes line up at the equator of the spindle. This is a crucial step in cell division, specifically in mitosis. In metaphase, the chromosomes become fully condensed and are attached to the spindle fibers by their centromeres. They align in a single file line along the metaphase plate or equator of the cell. This alignment ensures that each daughter cell will receive the correct number and type of chromosomes during cell division.

A karyotype is a physical map of an array of chromosomes in an organism. It provides a visual representation of the number, size, and shape of chromosomes in an individual's cells. This allows for the identification of any structural abnormalities or genetic disorders. The other options, such as ecotype, haplotype, phenotype, and genotype, are not directly related to the physical mapping of chromosomes and do not accurately describe a karyotype.

Before cell division, each homologue replicates into two identical copies called sister chromatids. These sister chromatids are connected by a centromere. They contain the same genetic information and are held together until they separate during cell division. Therefore, the correct answer is sister chromatids.

Plant cells typically achieve cytokinesis by forming a cell plate across the middle of the cell. This process involves the formation of a new cell wall that separates the two daughter cells. The cell plate is formed by the fusion of vesicles containing cell wall materials, and it gradually expands outwards until it reaches the edges of the cell. This mechanism allows for the division of the cytoplasm and organelles between the two daughter cells, ensuring their proper development and growth.

Eukaryotic chromosomes are coated with proteins containing a high proportion of basic amino acids. These proteins are called histones. Histones play a crucial role in DNA packaging and organization within the nucleus. They help in the formation of nucleosomes, which are the basic units of chromatin structure. Histones also regulate gene expression by controlling access to DNA. Therefore, histones are essential for maintaining the integrity and functionality of eukaryotic chromosomes.

Animal cells typically achieve cytokinesis by forming a cleavage furrow that pinches the cell into two. This process involves the contraction of a ring of actin and myosin filaments, which creates a furrow or indentation in the cell membrane. The furrow deepens until it eventually divides the cytoplasm into two separate daughter cells. This method of cytokinesis is different from binary fission, which is a form of cell division used by prokaryotic cells, and from the formation of a cell plate, which is characteristic of plant cells. Chromosome condensation and elongation are not directly involved in cytokinesis.

In humans, body cells (non-sex cells) contain two sets of chromosomes totaling 46. This is because humans are diploid organisms, meaning they have two copies of each chromosome, one inherited from each parent. Each set of chromosomes consists of 23 pairs, with one pair being the sex chromosomes (XX in females and XY in males) and the other 22 pairs being autosomes. Therefore, when the two sets of chromosomes are combined, the total number of chromosomes in human body cells is 46.

The correct answer, "+ + S," represents the interphase stage of the cell cycle. Interphase is the longest phase of the cell cycle where the cell prepares for division by growing and replicating its DNA. The "+ + S" notation indicates that the cell is in the G1 phase, where it grows and carries out normal cellular functions, followed by the S phase, where DNA replication occurs.

During prophase, the first stage of mitosis, the chromosomes condense and become shorter and thicker. This is achieved through a process called chromatin condensation. The condensation allows the chromosomes to become more visible under a microscope and facilitates their movement during cell division. In anaphase, the chromosomes separate and move towards opposite ends of the cell. Interphase is the stage between cell divisions. Metaphase is the stage when the chromosomes align at the center of the cell. Telophase is the final stage when the chromosomes reach the opposite ends of the cell and the nuclear envelope reforms.

During interphase of the cell cycle, the cell undergoes three phases: G1 (Gap 1), S (Synthesis), and G2 (Gap 2). In the G1 phase, the cell grows and carries out its normal functions. The S phase is when DNA replication occurs, resulting in the duplication of the cell's genetic material. The G2 phase is a period of further growth and preparation for cell division. The M phase, or mitosis, is the phase where the cell actually divides into two daughter cells. Therefore, the correct answer is M, as it does not occur during interphase.

Telophase is essentially the reverse of prophase because it is the final stage of mitosis, while prophase is the initial stage. During prophase, the nuclear envelope breaks down, chromosomes condense, and the spindle apparatus forms. In telophase, the nuclear envelope reforms, chromosomes decondense, and the spindle apparatus disassembles. This reversal of events marks the completion of cell division and the return to a resting state.

Cytokinesis is the process of dividing the cytoplasm of a cell into two daughter cells. It occurs after the nuclear division (mitosis or meiosis) is complete. Telophase is the final stage of nuclear division, where the chromosomes have reached opposite poles of the cell and are starting to decondense. At this stage, the cell membrane starts to pinch inwards, eventually leading to the formation of two separate daughter cells. Therefore, cytokinesis occurs right after telophase.

During anaphase, microtubules become shorter and contract, causing the chromatids to separate and move towards opposite ends of the spindle. This movement ensures that each daughter cell will receive a complete set of chromosomes during cell division.

The correct answer is spindle apparatus. The spindle apparatus is a structure made up of microtubules that forms during cell division. It plays a crucial role in moving the chromatids apart, ensuring that each daughter cell receives the correct number of chromosomes. The spindle apparatus helps to organize and separate the chromosomes during both mitosis and meiosis. It is responsible for the proper alignment and segregation of the chromosomes, ensuring the formation of two genetically identical daughter cells. The other options mentioned (aster, cell plate, centriole, and centromere) are not directly involved in moving the chromatids apart during cell division.

The correct answer is cyclins and cyclin-dependent kinases. Cyclins are proteins that regulate the progression of the cell cycle by binding to cyclin-dependent kinases (CDKs) and activating them. CDKs are enzymes that control the cell cycle by phosphorylating target proteins and initiating specific events in each phase of the cell cycle. Together, cyclins and CDKs form a complex that regulates the checkpoints for cell cycle control, ensuring proper cell division and preventing abnormal cell growth. Microtubules, asters, histones, and channel proteins are not directly involved in the functioning of the checkpoints for cell cycle control.

Histones are proteins that are tightly bound to the double strands of DNA. They play a crucial role in DNA packaging, as they help in organizing and condensing the DNA into a compact structure called chromatin. This compact structure allows the DNA to fit inside the nucleus of a cell. Histones also play a role in gene regulation, as they can control the accessibility of DNA to transcription factors and other proteins involved in gene expression. Therefore, studying histones can provide insights into the structure and function of DNA, as well as the regulation of gene expression.

Prior to mitosis in the cell cycle, the cell is in the phase where the chromosomes have all been copied through DNA replication and are now sister chromatids. During this phase, each chromosome is duplicated to form two identical sister chromatids that are held together at the centromere. This ensures that each daughter cell receives an exact copy of the genetic material during cell division. The other statements are not true for this phase of the cell cycle.

Mutations in the Rb and p53 proteins are most commonly associated with cancers. Rb (Retinoblastoma) and p53 (Tumor protein 53) are tumor suppressor proteins that play crucial roles in regulating cell division and preventing the formation of tumors. Mutations in these proteins can lead to their inactivation or loss of function, allowing uncontrolled cell growth and the development of cancer. Therefore, the presence of mutations in Rb and p53 is frequently observed in various types of cancers.

The number of chromosomes in eukaryotes can vary greatly from 2 to over 1000 in different species. This means that different species can have a different number of chromosomes, which is not determined by the size of the organism or can be predicted without the use of a microscope. Additionally, the number of chromosomes can vary depending on the type of cell within the same organism.

During prophase, the chromosomes condense and become visible. This condensation process causes the nucleolus, which is responsible for ribosomal RNA synthesis, to disappear. The nucleolus is a distinct structure within the nucleus where ribosomes are assembled. As the chromosomes condense, the nucleolus breaks down and disperses, temporarily ceasing ribosomal RNA synthesis. Therefore, the correct answer is "nucleolus disappear."

Recent studies have shown that animal cells have the ability to override the inhibitory controls of cell division using certain factors. These factors are known as growth factors. Growth factors are proteins that stimulate cell division and promote cell growth. They play a crucial role in regulating the cell cycle and ensuring proper cell division. Therefore, growth factors are the correct answer in this context.

Cytokinesis is the correct answer because it refers to the process of dividing the cytoplasmic material into two daughter cells. It occurs after mitosis, which is the division of the nucleus, and is responsible for the physical separation of the two cells. DNA replication is the process of copying the genetic material, and binary fission is a form of cell division in prokaryotes.

The correct answer is "G to S to G2 to M to C". This sequence of cell-cycle phases is characteristic of eukaryotes. In the G1 phase, the cell grows and carries out its normal functions. Then, it enters the S phase where DNA replication occurs. After S phase, the cell enters the G2 phase where it continues to grow and prepares for cell division. The M phase is the mitotic phase where the cell undergoes nuclear division (mitosis) and cytoplasmic division (cytokinesis). Finally, the cell enters the C phase (G0 phase) where it rests or exits the cell cycle.

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The correct answer is C. The phase of the cell cycle during which the cytoplasm divides to form two cells is called cytokinesis. During cytokinesis, the cytoplasmic contents are divided equally between the two daughter cells, resulting in the formation of two separate cells. This phase follows the mitotic phase (M phase) where the nucleus divides, and it marks the completion of the cell division process.

Microtubules are responsible for the proper separation of sister chromatids during cell division. They form the mitotic spindle, a structure that attaches to the kinetochores of the sister chromatids and guides their movement towards opposite poles of the cell. Without the attachment of microtubules to the kinetochores, the sister chromatids would not be able to separate correctly, leading to errors in chromosome distribution and potentially causing genetic abnormalities. Therefore, the attachment of microtubules is critical for the proper separation of sister chromatids.

The checkpoint for cell cycle control in a eukaryotic cell is a mechanism that ensures the cell progresses through each phase of the cell cycle accurately. The "S" checkpoint ensures that DNA replication is complete and accurate before the cell enters the next phase. The "M" checkpoint ensures that all chromosomes are properly attached to the spindle fibers before the cell proceeds to divide. The spindle checkpoint checks for proper chromosome alignment during metaphase. However, "MFP" is not a known checkpoint for cell cycle control in a eukaryotic cell.

The bacterial genome is a single, circular, uncoated, double stranded DNA molecule. This means that the DNA in bacteria is organized into a single circular structure, rather than multiple separate pieces. It is also double stranded, meaning it consists of two complementary strands of DNA that are intertwined. The DNA molecule is uncoated, meaning it does not have a protein coat like some viruses do. This structure is characteristic of bacterial genomes and allows for efficient replication and gene expression.

During mitosis, the cell undergoes replication of its chromosomes, resulting in two identical sets of chromosomes. The process of cytokinesis then separates the cytoplasm and organelles, creating two new daughter cells. Since each daughter cell receives an identical set of chromosomes, the number of chromosomes remains the same as the original cell, which is 32 in this case. Therefore, each new daughter cell will have 32 chromosomes.

Homologous chromosomes refer to the two copies of each chromosome in body cells. These chromosomes are similar in size, shape, and carry the same genes, although they may have different versions of those genes. During sexual reproduction, homologous chromosomes pair up and exchange genetic material through a process called crossing over. This ensures genetic diversity in offspring. Therefore, homologous chromosomes are the correct term to describe the two copies of each chromosome in body cells.

Binary fission is the correct answer because it is the actual process of cell division in prokaryotic cells. Unlike eukaryotic cells, which undergo mitosis or meiosis, prokaryotic cells divide through binary fission. In this process, the DNA replicates, and the cell membrane pinches inward, dividing the cell into two identical daughter cells. Cytokinesis, on the other hand, is the process of dividing the cytoplasm and organelles between daughter cells and is a part of both mitosis and meiosis.

Mitosis is the correct answer because it refers to the process of nuclear division in eukaryotic cells. During mitosis, the nucleus of a cell divides into two identical daughter nuclei, each containing the same number of chromosomes as the parent cell. This process is important for growth, repair, and asexual reproduction in multicellular organisms. Meiosis, on the other hand, is a type of nuclear division that occurs in the formation of gametes (sex cells) and results in the production of cells with half the number of chromosomes. Binary fission is a type of cell division in prokaryotic cells, while cytokinesis refers to the division of the cytoplasm following nuclear division.

During the S phase of the cell cycle, DNA replication occurs, resulting in the formation of sister chromatids. Each chromosome is composed of two sister chromatids, which are identical copies of each other. Since humans have 23 pairs of chromosomes, after the S phase, there would be 46 pairs of sister chromatids. Additionally, each sister chromatid contains a single DNA molecule, so there would be a total of 92 individual DNA molecules.

The cell organelles replicate prior to genomic separation in S phase. During the S phase of the cell cycle, DNA replication occurs, which includes the replication of cell organelles such as mitochondria and chloroplasts. This ensures that each daughter cell receives a complete set of organelles during cell division. The M phase is when genomic separation occurs, with the cell dividing into two daughter cells. The C phase does not exist in the context of the cell cycle phases.

The given question is incorrect as it states that the process of cell division in eukaryotic cells is called binary fission, which is actually the process of cell division in prokaryotic cells. In eukaryotic cells, the correct term for cell division is mitosis, where the cytoplasm splits into two daughter cells. Meiosis is a different process that occurs in eukaryotic cells to produce gametes for sexual reproduction. Cytokinesis is the final stage of cell division, where the cytoplasm divides and two daughter cells are formed.