Question

Пресинтетический период Процесс, происходящий в клетке Синтетический период Постсинтетический период Количество хромосом (n)и содержание ДНК (c) Профаза (первая фаза митоза) Метафаза (фаза скопления хромосом) Анафаза (фаза расхождения хромосом) Телофаза (фаза окончания деления)

Answer 1

В митозе
пресинт. 2n2c
синтетич. 2n4c
постсинт. 2n4c
профаза 2n4c
метафаза 2n4c
анафаза 2n2c
телофаза 2n2c

Answer 2

Synthetic Period in Cell Cycle

The cell cycle is a series of events that occur in a cell leading to its division and the production of two daughter cells. It consists of several phases, including the synthetic period.

During the synthetic period, also known as the S phase, the cell undergoes DNA replication. This means that the genetic material, which is stored in the form of chromosomes, is duplicated. The DNA replication process ensures that each daughter cell receives an identical copy of the genetic material.

The synthetic period is a crucial step in the cell cycle as it ensures the accurate transmission of genetic information to the next generation of cells. It is followed by the post-synthetic period.

Post-Synthetic Period in Cell Cycle

The post-synthetic period, also known as the G2 phase, is the second gap phase in the cell cycle. During this phase, the cell prepares for cell division by synthesizing proteins and organelles needed for the upcoming mitotic phase. The cell also undergoes a series of checks to ensure that the DNA replication during the synthetic period was accurate and complete.

The post-synthetic period serves as a quality control checkpoint before the cell proceeds to the next phase, which is mitosis. If any errors or abnormalities are detected during this phase, the cell cycle may be arrested, and repair mechanisms may be activated to fix the issues. Once the cell passes the checks, it enters the mitotic phase.

Chromosome Number (n) and DNA Content (c)

The chromosome number (n) refers to the number of unique chromosomes present in a cell. It represents the haploid number of chromosomes, which is the number of chromosomes in a gamete (sex cell). In humans, the haploid number is 23.

The DNA content (c) refers to the amount of DNA present in a cell. It is usually measured in picograms (pg) or as a DNA content index (2c, 4c, etc.). The DNA content is directly related to the chromosome number, as each chromosome contains a specific amount of DNA.

During the synthetic period, the DNA content doubles as the cell undergoes DNA replication. This ensures that each daughter cell receives the correct amount of DNA during cell division.

Phases of Mitosis

Mitosis is the process of cell division that occurs after the synthetic and post-synthetic periods. It consists of several phases, including prophase, metaphase, anaphase, and telophase.

- Prophase: During prophase, the chromatin condenses into visible chromosomes, and the nuclear envelope breaks down. The centrosomes move to opposite poles of the cell, and spindle fibers begin to form.

- Metaphase: In metaphase, the chromosomes align along the equatorial plane of the cell. The spindle fibers attach to the centromeres of the chromosomes, ensuring their proper alignment.

- Anaphase: Anaphase is characterized by the separation of sister chromatids. The spindle fibers contract, pulling the sister chromatids apart and towards opposite poles of the cell.

- Telophase: Telophase marks the end of mitosis. The chromosomes reach the opposite poles of the cell, and a new nuclear envelope forms around each set of chromosomes. The cell begins to divide, leading to cytokinesis.

It is important to note that the cell cycle and its phases are highly regulated processes that ensure the accurate transmission of genetic material and the proper division of cells. Any disruptions or abnormalities in these processes can lead to genetic disorders or diseases.