biology lecture quiz 5
Mitosis and cell cycle terminology As in most areas of biology, the study of mitosis and the cell cycle involves a lot of new terminology. Knowing what the different terms mean is essential to understanding and describing the processes occurring in the cell. Drag the terms on the left to correctly complete these sentences. Not all the terms will be used. 1. DNA replication produces two identical DNA molecules, called _______________ , which separate during mitosis. 2. After chromosomes condense, the ______________ is the region where the identical DNA molecules are most tightly attached to each other. 3. During mitosis, microtubules attach to chromosomes at the ________________ . 4. In dividing cells, most of the cell's growth occurs during ______________ . 5. The __________________ is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division. 6. During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called _____________________ . 7. In most eukaryotes, division of the nucleus is followed by _____________ , when the rest of the cell divides. 8. The _________________ are the organizing centers for microtubules involved in separating chromosomes during mitosis.
1. sister chromatids 2. centromeres 3. kinetochores 4. interphase 5. mitotic spindles 6. chromatin 7. cytokinesis 8. centrosomes The key structures involved in mitosis are labeled in this diagram of an animal cell that shows the two sister chromatids of each duplicated chromosome beginning to attach to the mitotic spindle by means of their kinetochores. The centrosomes anchor the mitotic spindle at opposite ends of the cell.
Phases of the cell cycle The cell cycle represents the coordinated sequence of events in the life of a cell from its formation to its division into two daughter cells. Most of the key events of the cell cycle are restricted to a specific time within the cycle. In this exercise, you will identify when various events occur during the cell cycle. Recall that interphase consists of the G1, S, and G2 subphases, and that the M phase consists of mitosis and cytokinesis.
Many organisms contain cells that do not normally divide. These cells exit the cell cycle before the G1 checkpoint. Once a cell passes the G1 checkpoint, it usually completes the cell cycle--that is, it divides. - The first step in preparing for division is to replicate the cell's DNA in the S phase. - In the G2 phase, the centrosome replicates. - In early M phase, the centrosomes move away from each other toward the poles of the cell, in the process organizing the formation of the mitotic spindle. - At the end of the M phase when mitosis is complete, the cell divides (cytokinesis), forming two genetically identical daughter cells.
Why do some species employ both mitosis and meiosis, whereas other species use only mitosis? - Why do some species employ both mitosis and meiosis, whereas other species use only mitosis? -They need meiosis if the cells are producing organs such as ovaries. -They need only meiosis if they produce egg cells. -They need only mitosis to make large numbers of cells such as sperm. -A single-celled organism only needs mitosis. -They need both if they are producing animal gametes.
They need both if they are producing animal gametes. (The form of cell division that produces animal gametes is meiosis, not mitosis. The production of gametes in plants is a function of both mitosis and meiosis.)
