chapter 12 Flashcards
Why do unicellular organisms undergo cell division?
in order to reproduce
Why do multicellular organisms undergo cell division?
Growth and repair
Gamete cells
cells produced by multicellular organisms when they produce sperm and egg (reproductive) cells. Gamete cells are haploid.
Somatic cells
all of the other cells of the body (besides sex cells). Somatic cells are diploid.
Why are the terms “n” and “2n” used to symbolize haploid and diploid?
The number of chromosome types are represented by the letter n. If the cell is 2n that means it has two copies of each type of chromosome
If 2n = 6, then what does n equal?
3
How do haploid and diploid relate to homologous chromosome pairs?
A cell that is n has only one of the homologous pair. A cell that is 2n has both chromosomes of the homologous pair.
What are the two phases of the cell cycle?
Interphase and the mitotic phase
During which of the phases of the cell cycle does the cell spend 90% of its time?
Interphase
What is mitosis?
Division of the nucleus to produce two genetically identical daughter cells
What is cytokinesis?
Division of the cytoplasm
What is the relationship between mitosis and cytokinesis?
They overlap to allow for proper division of the cell. Cytokinesis overlaps with the last two phases of mitosis.
Phases of Mitosis
Prophase, prometaphase, metaphase, anaphase, telophase (& cytokinesis)
Prophase
the chromosomes are located inside the nuclear envelope, are still in their replicated form, and the mitotic spindle is just starting to form
Prometaphase
the nuclear envelope dissolves so the chromosomes (still in their replicated form) are no longer in the nucleus, the aster has fully formed and kinetochore microtubules have attached to both sides of the centromere of each chromosome
Metaphase
the replicated chromosomes line up along the metaphase plate
Anaphase
Enzymes cut through the cohesin proteins and centromere holding the sister chromatids together, the kinetochore microtubules shorten to pull the (no longer replicated) chromosomes to opposite ends of the cell, nonkinetochore microtubules grow to start to lengthen the cell in preparation for division
Telophase (& cytokinesis)
nuclear envelope reforms, the unreplicated chromosomes decondense, cytoplasm divides, a cleavage furrow forms and grows along the metaphase plate, microfilaments tighten at the metaphase plate splitting the cell into two causing the formation of two daughter cells
Animal cell cytokinesis
a cleavage furrow forms and grows along the metaphase plate, microfilaments tighten at the metaphase plate splitting the cell into two causing the formation of two daughter cells
Plant cell cytokinesis
vesicles containing the substances of the cell well group together at the metaphase plate, fuse, and form a cell plate that eventually reaches all the way across the cell, splitting the cell into two
daughter cell
cell that results from division
gametes
egg or sperm cells with half of the original amount of DNA
aster
the star shaped structure made of microtubules that anchors the centrosome to the cytoskeleton
chromatin
mix of DNA and histone proteins that make up the chromosomes
nuclear envelope
double membrane that surrounds the DNA
nuclear envelope fragmentation
when the envelope dissolves in mitosis
chromosome condensation
when the chromosomes condense during mitosis
centrosome
the structure from which the mitotic spindle forms
centriole
part of the centrosome from which the spindle fibers grow
mitotic spindle
consists of the aster, kinetochore microtubules, and nonkinetochore microtubules
metaphase plate
equator of the cell where chromosomes line up and where the cell splits
cell plate
partial cell wall formed at metaphase plate when a new cell wall is developing between two newly divided cells
cleavage furrow
furrow that forms at the metaphase plate of the cell during cytokinesis
cleavage
the separation of two structures
