Bio 103 - Chapter 12 (2) -pharmacgy

Explanation
In a cell, each chromosome consists of two sister chromatids joined together by a centromere. Since there are 20 chromatids in the cell, it means there are 10 pairs of sister chromatids, and hence 10 centromeres.

Explanation
The spindle is a structure involved in cell division and includes asters, spindle microtubules, and the centrosome. Asters are star-shaped structures formed around the centrosome that help in the movement and positioning of the spindle. Spindle microtubules are long protein filaments that make up the main structure of the spindle and are responsible for separating the chromosomes during cell division. The centrosome is an organelle that contains the centrioles and plays a crucial role in organizing the spindle. Therefore, all of the mentioned options are correct components of the spindle.

Explanation
During metaphase in animal cells, the centrioles begin to move apart. Metaphase is the stage of mitosis where the chromosomes align along the equatorial plane of the cell. The centrioles, which are responsible for organizing the microtubules that form the spindle fibers, start to separate and move towards opposite poles of the cell. This movement of the centrioles is essential for the proper alignment and segregation of the chromosomes during cell division.

Explanation
During mitosis in both plant and animal cells, the microtubules of the spindle originate from the centrosome. The centrosome is a structure located near the nucleus that contains a pair of centrioles. These centrioles play a crucial role in organizing the microtubules and forming the spindle apparatus. The spindle is responsible for separating the chromosomes during cell division. Therefore, the correct answer is centrosome.

Explanation
During anaphase, the chromatids separate and become individual chromosomes. This is the stage where the sister chromatids are pulled apart by the spindle fibers towards opposite poles of the cell. As the chromatids move towards the poles, they condense and become distinct chromosomes. Therefore, anaphase is the phase of mitosis where the chromatids become chromosomes.

Explanation
During metaphase of mitosis, each chromosome consists of two sister chromatids. Since there are 92 chromatids, it means there are 46 chromosomes (92/2) in the cell. During completion of mitosis, the cell would divide into two daughter cells, each containing the same number of chromosomes as the parent cell, which is 46 chromosomes. Therefore, the correct answer is 46.

Explanation
During the G1 (Gap 1) stage of the cell cycle, the cell prepares for DNA replication and growth. It synthesizes RNA and proteins needed for cell function and division. This stage is also when the cell produces some organelles necessary for protein synthesis, such as ribosomes. Therefore, G1 is the stage at which the cell can produce protein and some organelles.

Explanation
During anaphase, the centromere splits, allowing the sister chromatids to separate and move towards opposite poles of the cell. This separation is facilitated by the action of an enzyme that breaks down the protein complexes responsible for holding the sister chromatids together, known as cohesion. Therefore, anaphase is the phase in which both centromere split and cohesion separate.

Explanation
In unicellular eukaryotes, cell division is primarily for reproduction. Unicellular organisms reproduce by dividing into two daughter cells, each identical to the parent cell. This process, known as binary fission, allows the organism to multiply and increase its population. Cell division in unicellular eukaryotes is not primarily for growth, repair, or fertilization, as these processes are more relevant in multicellular organisms.

Explanation
Most cell division, such as mitosis, results in genetically identical daughter cells. During mitosis, the DNA is replicated and then distributed equally between the two daughter cells. This ensures that each daughter cell receives an identical copy of the genetic material. However, there are some exceptions to this rule, such as meiosis, which is a type of cell division that results in genetically unique daughter cells.

Explanation
Chromatin is a complex of DNA and proteins that makes up the genetic material in the nucleus of a cell. It is formed by the packaging of DNA around proteins called histones, which help to organize and compact the DNA. The DNA + Protein option is the correct answer because chromatin is composed of both DNA and proteins.

Explanation
The cell cycle consists of two main phases: interphase and mitotic phase. Interphase is the longest phase and includes G1, S, and G2 phases. During interphase, the cell grows, replicates its DNA, and prepares for cell division. The mitotic phase, also known as M phase, includes mitosis and cytokinesis. Mitosis is the process of dividing the cell's nucleus into two identical daughter nuclei, while cytokinesis is the division of the cytoplasm to form two separate cells. Therefore, the correct answer is "Mitotic phase, interphase."

Explanation
During prophase, the chromatin fibers condense and become tightly coiled, forming distinct chromosomes. This condensation allows for easier separation and movement of the genetic material during cell division. Therefore, it can be concluded that the condensation of chromatin occurs in prophase.

Explanation
The mitotic phase, which includes the processes of mitosis and cytokinesis, is the phase in the cell cycle where the cell divides to form two identical daughter cells. This phase alternates with interphase, which is the phase where the cell grows, carries out its normal functions, and replicates its DNA in preparation for cell division. Therefore, the statement that the mitotic phase alternates with interphase in the cell cycle is true.

Explanation
The eukaryotic cell cycle is indeed regulated by a molecular control system. This system ensures that the cell progresses through the different phases of the cell cycle in a coordinated and controlled manner. The control system involves various molecules such as cyclins and cyclin-dependent kinases (CDKs) that work together to regulate the cell cycle checkpoints and ensure accurate DNA replication and cell division. This molecular control system is crucial for maintaining the integrity and stability of the cell cycle and preventing uncontrolled cell growth and division.