Cell cycle Flashcards
REMEMBER!
Cells have distinct phases of growth, reproduction, and normal functions!
The cell cycle has four main stages!
Cells divide at different rates!
Cell size is limited!
What is the definition of the cell cycle?
The cell cycle is the regular pattern of growth, DNA replication, and cell division that occurs in eukaryotic cells. The cell cycle has four main stages: gap 1, synthesis, gap 2, and mitosis.
What happens during these four stages?
Mitosis (M) (Prophase, Metaphase, Anaphase, Telophase, (Cytokinesis)): Cell division >The fourth stage of the cell cycle
Gap 1 (G1): Cells grow, carry out normal functions, and replicate their organelles. >The first stage of the cell cycle
Synthesis (S): DNA synthesis >The second stage of the cell cycle
Gap 2 (G2): Additional growth >The third stage of the cell cycle
Explain in more detail the first stage of the cell cycle, gap 1 (G1).
During this stage, a cell carries out its normal functions. Cells also increase in size, and organelles increase in number. G1 is also a stage where the cell must pass a critical checkpoint before it can proceed to the synthesis stage. Otherwise, it would be dangerous for a cell to continue dividing if certain conditions are not met.
Explain in more detail the second stage of the cell cycle, synthesis (S).
During the S stage, the cell makes a copy of its nuclear DNA. By the end of this stage, the cell nucleus contains two complete sets of DNA. >The word “synthesis” means “the combining of parts to make a whole.”
Explain in more detail the third stage of the cell cycle, gap 2 (G2).
During this stage, cells continue to carry out their normal functions, and additional growth occurs. Like the G1 stage, this stage also includes a critical checkpoint. Everything must be in order - adequate size, undamaged DNA - before the cell goes through mitosis and division.
Explain in more detail the fourth and last stage of the cell, mitosis (M).
The stage M includes two processes: mitosis and cytokinesis. Mitosis is the division of the cell nucleus and its contents. During mitosis, the nuclear membrane dissolves, the duplicated DNA condenses around proteins and separates, and two new nuclei form. Lastly, cytokinesis is the process that divides the cell cytoplasm. the result is two daughter cells that are genetically identical to the original cell (mother cell).
What is DNA replication?
DNA replication is also called DNA synthesis. During this process, the DNA molecule unzips and each strand is used as a pattern for a new DNA strand. Actually, this is a process by which the DNA makes a copy of itself during cell division.
What is the asexual reproduction?
Asexual reproduction is a type of reproduction by which offspring from a single organism, and inherit the genes of that parent only; it does not involve the fusion of gametes, and almost never changes the number of chromosomes. Asexual reproduction is the primary form of reproduction for single-celled organisms such as the Archaea and the bacteria. Many plants and fungi reproduce asexually as well. During mitosis (M) (cell division) asexual reproduction occurs.
What are gametes?
Gametes are the reproductive cells used during sexual reproduction to produce a new organism called a zygote (diploid cell). The gametes in males and females are different. The male gamete is called sperm and the female gamete is called an egg or ova. Male and female gametes are formed during a process of cellular reproduction called meiosis.
Explain the term “meiosis.”
Meiosis is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them. This process occurs in all sexually reproducing single-celled and multicellular eukaryotes, including animals, plants, and fungi.
What can we say about the rates of cell division?
Rates of cell division vary widely. The rate at which your cells divide is linked to your body’s need for those cells. In human cells, the S, G2, and M stages together usually take about 12 hours. The lenght of the G1 stage differs most from cell type to cell type.
What is special about the G0 stage?
Cells that divide only rarely and occasionally (for example in response to injury or cell death >smooth muscle cells of the intestine) are thought to enter a stage that some scientists call G0. In G0, cells are unlikely to divide, although they continue to carry out their normal functions.
How are lymphocytes related to the G0 stage?
Lymphocytes are a type of white blood cell and they are part of our immune system. There are two major types of lymphocytes, B and T cells. Lymphocytes may remain in G0 for years until they recognize an invader. Once the invader binds to a lymphocyte receptor, the lymphocyte goes through rapid cell divisions to help fight the infection.
How can we judge the limited size of cells?
Cells have upper and lower cell limits. If cells were too small, they could not contain all of the necessary organelles and molecules. However, cells cannot grow beyond a certain size, even if surrounded by plenty of nutrients. The upper limit on cell size is due to the ratio of cell surface area to volume.
