Chapter 17 Flashcards
Purpose of Cell Division
- Multicellular eukaryotic organisms to arise from a single fertilized egg (zygote)
- Growth and maintenance (replacement of old or damaged cells with new ones)
Somatic Cells vs. Gametes
Somatic Cells: all non sexual cells of the body, Mitosis
Gametes: Sex cells (sperm and egg), Meiosis
Chromosomes
Chromosomes are thread-like structures located inside the nucleus of animal and plant cells, made of nucleic acids (DNA) and proteins.
Types of Chromosomes
-Uncondensed (cannot be seen under light microscope, long and skinny)
- Condensed (can be seen under light microscope, thick shortie)
Chromatid
one of the two identical halves of a chromosome that has been replicated in preparation for cell division
Phases of Cell Cycle
Interphase (90% of cell cycle)
Mitotic Phase (10% of cell cycle)
Stages of Interphase
- Gap 1
- S phase
- Gap 2
Gap 1
Cell growth before DNA replication; cell functioning (normal)
S phase
Synthesis of DNA; DNA is duplicated (single to double stranded for future cell division)
Gap 2
Cell prepares for cell division (mitosis) by building proteins and organelles, and begins to reorganize its contents in preparation for mitosis
Mitotic Phase Stages
- Prophase
- Metaphase
- Anaphase
- Telophase
Prophase
Chromosomes become visible as they shorten and thicken (i.e condensed), centriole in cytoplasm divides and moves to opposite poles of cells; provide attachment or spindle fibers.
- Nuclear membrane fades; nucleolus disappears
Metaphase
Sister chromatids move toward center of cell, equatorial plate.
- Chromosomes appear as dark, thick masses attached to spindle fibers
Spindle Fibers
In cell biology, the spindle apparatus is the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells.
Anaphase
Centromeres divide; chromatids move to opposite poles of cell
Telophase
Spindle fibers dissolve: nuclear membrane begins to form around each mass of chromatin
Cytokinesis
Division of cytoplasm and distribution of organelles to “daughter” cells; occurs during telophase. Pinches off in center as cytoplasm moves to opposite poles; cell membrane pinches to form 2 separate daughter cells, forming the “cleavage”
A Cell Clock
A biological clock regulates the # of cell division. Immature cells always completed 50 division no matter
Why cells stop dividing
- Senescence: process of aging, progression of irreversible change that eventually leads to death
- Cell Specialization: the more specialized a cell, the less able it is to undergo mitosis. Eg. Neuron
Difference between twin formation
Identical twins are a single zygote divided in two vs. Fraternal twins who are two separate zygotes in the same womb
How Animals are Cloned
They extract nucleus from an unfertilized egg cell and insert a nucleus from a cell of a separate organism, cell is in blastula and the egg cell with transplanted nucleus grows normally and the adult becomes a clone of the nucleus donor
- Mammal cell cloning is more difficult
Totipotent
Cancer Cells
The result of rapidly uncontrollably grown cells
Metastasis
The spread of cancer cells from the place where they first formed to another part of the body
