Ch.12: The Cell Cycle Flashcards
The continuity of life is based on the reproduction of cells, or
cell division
What do all organisms and cells have in common
All organisms are composed of cells
Cells reproduce themselves
division of one cell reproduces the entire organism
unicellular organisms
Multicellular organisms depend on cell division for:
Development
Growth/Repair
Asexual reproduction
the division of the nucleus
mitosis
the division of the cytoplasm
cytokinesis
What must be divided perfectly during mitosis, and Why?
chromosomes, so that it resembles the parent cell perfectly
All the DNA in a cell constitutes the cell’s _________; can consist of a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells)
genome
(body cells) have two sets of chromosomes (Diploid=2n)
Somatic Cells
(sperm and eggs) have only one set of chromosomes (Haploid=n)
Gametes
When cells are not dividing the DNA is in the form of _________; DNA and protein that are uncondensed and functional
Chromatin
In preparation for cell division, what occurs
DNA must be replicated and the chromosomes formed
Each duplicated chromosome has
two sister chromatids (must separate)
The __________ is the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached
centromere
The cell cycle consists of
Mitotic phase (mitosis & cytokinesis) Interphase (cell growth and copying of chromosomes in preparation for cell division)
Interphase:
about 90% of the cell cycle) can be divided into subphases: G1 phase (“first gap”) S phase (“synthesis”) Where DNA is replicated G2 phase (“second gap”)
Mitosis is conventionally divided into five phases:
Prophase Prometaphase Metaphase Anaphase Telophase
an apparatus of microtubules that controls chromosome movement during mitosis
mitotic spindle
During prophase, assembly of spindle microtubules begins in the ___________; it replicates, forming two XXXXXX that migrate to opposite ends of the cell, as spindle microtubules grow out from them
centrosome
What happens in ANAPHASE
sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell
The microtubules shorten by depolymerizing at their kinetochore ends
In animal cells, cytokinesis occurs by a process known as cleavage, forming a
cleavage form
In plant cells, a _____ _____ forms during cytokinesis
cell plate
The sequential events of the cell cycle are directed by a distinct____ ______ _____, which is similar to a clock; regulated by both internal and external controls. clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received
cell cycle control system
The checkpoints are
G1, G2, & M
checkpoint seems to be the most important one
If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the S, G2, and M phases and divide
G1
If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the
G0 phase
Type of cells do not respond normally to the body’s control mechanisms
cancer cells
Cancer cells may not need growth factors to grow and divide:
They may make their own growth factor
They may convey a growth factor’s signal without the presence of the growth factor
They may have an abnormal cell cycle control system
A normal cell is converted to a cancerous cell by a process called
transformation
masses of abnormal cells within otherwise normal tissue
tumors
If abnormal cells remain at the original site, the lump is called a
benign tumor
invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body
malignant tumor
