Flashcards in Chapter 12 Deck (58):
the continuity of life...the reproduction of cells
what type of cell division happens in unicellular organisms?
division of one cell reproduces the entire organism
multi cellular organisms depend on cell division for... (3 things)
-development from a fertilized cell
most cell division results in ______ cells with identical ___.... and what is the exception?
*the exception is meiosis, a special type of division that can produce sperm and egg cells
all of the DNA in a cell
-can consist of a single DNA molecule (prokaryotic cells)
-can consist of a number of DNA molecules (eukaryotic cells)
DNA molecules in a cell are packaged in the chromosome
-remember a chromosome can look like an x but it can also look like an / because it is the same chromosome just a replica so you say it is still one chromosome
chromatin (definition and where do you find chromatin)
-a complex of DNA and protein that condenses during cell division
-found in eukaryotic cells
(nonreproductive cells) have two sets of chromosomes
(reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells
in preparation for cell division, ___ is replicated and the ___ condense
joined copies of the original chromosome which separate during cell division
the narrow "waist" of the duplicated chromosome, where the two chromatids are mostly attached
During cell division, the two sister chromatids ____ and ____ into two nuclei
once sister chromatids are separated into two nuclei what are they called?
eukaryotic cells consist of what type of cell division?
the division of the genetic material in the nucleus
the division of the cytoplasm
gametes being produced
What does the cell cycle consist of ?
-mitotic phase (M)
mitotic phase (M)
-mitosis and cytokinesis
-cell growth and copying of chromosomes in preparation for cell division
-is about 90% of the cell cycle
-G1 phase (first gap/growth)
-S Phase (synthesis)
-G2 phase (2nd gap/growth)
***the cell grows in all 3 phases, but chromosomes are duplicated only during the S phase
mitosis is divided into what 5 phases?
***cytokinesis overlaps the latter stages of mitosis (telophase)
what happens in G1 phase?
the cell synthesizes mRNA and proteins in preparation for subsequent steps leading to mitosis.
what happens in S Phase?
To produce two similar daughter cells, the complete DNA instructions in the cell must be duplicated. DNA replication occurs during this S (synthesis) phase.
what happens in G2 phase?
a safety gap during which a cell can check to make sure that the entirety of its DNA and other intracellular components have been properly duplicated. In addition to acting as a checkpoint along the cell cycle, G2 also represents the cell's final chance to grow before it is split into two independent cells during mitosis.
what happens in prophase?
Chromosomes become visible, the nucleolus disappears, the mitotic spindle forms, and the nuclear envelope disappears. Chromosomes become more coiled
what happens in prometaphase?
phosphorylation of nuclear lamins causes the nuclear membrane to break down into numerous small vesicles. As a result, the spindle microtubules now have direct access to the genetic material of the cell.
what happens in metaphase?
the alignment of chromosomes at the center of the cell
what happens in anaphase?
separation of sister chromatids to opposite mitotic spindle poles.
what happens in telophase?
the sister chromatids reach opposite poles. The small nuclear vesicles in the cell begin to re-form around the group of chromosomes at each end.
a structure made of microtubules that controls chromosome movement during mitosis
what begins in the centrosome?
the assembly of spindle microtubules...the centrosome is the microtubule organizing center.
when do cetrosomes replicate?
during interphase, which forms two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase
-a radial array of short microtubules
-extends from each centrosome
the spindle includes what 3 things?
2. the spindle microtubules
protein complexes associated with centromeres
what do spindle microtubules do during prometaphase?
attach themselves to the kinetochores of chromosomes and begin to move the chromosomes
how do microtubules pull chromatids to opposite parts of the cell?
the microtubules shorten by depolymerizing at their kinetochrome ends
nonkinetochore microtubules from opposite poles overlap and push against each other, elongating the cell
cytokinesis occurs by a process known as _____, forming a _____ _____ (IN ANIMAL CELLS)
cytokinesis IN PLANTS forms a ______
-the chromosome replicates (beginning at the origin or replication), and the two daughter chromosomes actively move apart
-plasma membrane pinches inward, dividing the cell into two
**much simpler than mitosis
mitosis evolved from ____ _____
the cell cycle appears to be driven by specific ____ _____ present int the cytoplasm
cell cycle control system
the sequential events of the cell cycle are directed by a distinct cell cycle control system
how many checkpoints are there? and what are their names?
1. G1 checkpoint
2. G2 checkpoint
3. M checkpoint
what does the G1 checkpoint do?
-if it is not needed or does not have the necessities to duplicate then it exits the cycle and destroys itself
-or it goes into a resting phase called the G0 phase (nondividing state)
what two types of regulatory proteins are involved in cell cycle control?
2. cyclin-dependent kinases (Cdks)
maturation-promoting factor (MPF)
a cyclin-Cdk complex that triggers a cell's passage past the G2 checkpoint into the M phase
growth factors (what is an example)
proteins released by certain cells that stimulate other cells to divide
density dependent inhibition (an external signal)
crowded cells stop dividing
what is an example of an internal signal?
when kinetochores are not attached to spindle microtubules send a molecular signal that delays anaphase
anchorage dependence (an external signal)
animal cells must be attached to a substratum (an underlying layer or substance) in order to divide
true or false: cancer cells exhibit neither density-dependent inhibition nor anchorage dependence
cancer cells do not need ____ ____ to grow and divide and why
-they make their own growth factors
-they convey (transport or carry to a place) a growth factor's signal without the presence of the growth factor
-they have an abnormal cell cycle control system
a normal cell being converted to a cancerous cell
abnormal cells remain at the original site