Biology 1115 Chapter 12
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What best distinguishes living things from non living things?
The ability of organisms to reproduce
What is cell division?
reproduction of cells
What is the function of cell division? (2)
- for growth and repair
- to reproduce
all the DNA in a cell
What are chromosomes?
a structure carrying genetic material(and protein), found in the nucleus of a eukaryotic cell
How many chromosomes do humans have?
Define somatic cells.
non-productive cells, which have 46 chromosomes (2 sets of 23)
Define gametes. How many do humans have?
- reproductive cells: sperm and eggs, which have half as many chromosomes as somatic cells
- 23 in humans
What is homologous? (2)
- same shape
- encodes same gene
What is cell cycle?
the life of a cell from formation to its own division
What happens in preparation for cell division?
DNA is replicated and the chromosomes condense
once copy of a duplicated chromosome
The part of a chromosome that links sister chromatids
What does the cell cycle consist of? Briefly explain each.(2)
- Interphase: cell growth and copying of chromosomes in preparation for cell division (longest stage, cell spends most of its life here)
- Mitotic (M) phase: mitosis and cytokinesis
Which stage is longest in cell division?
What are the five stages to mitosis?
When does cytokinesis get underway?
is well underway by late telophase
Which cytoskeleton component assists in the movement of chromosomes during cell division?
What is the mitotic spindle?
apparatus of microtubules that controls chromosome movement during mitosis
What is centrosome?
microtubule organizing center
What happens in prophase? (2)
- assembly of spindle microtubules begins in the centrosome
- centrosome replicates forming two centrosomes that migrate to opposite ends of the cell, as spindle microtubules grow out of them
What is an aster and what is its function?
- a radial array of short microtubules
- extends from each centrosome and attaches to the plasma membrane
what are the 3 things that spindles include?
centrosomes, spindle microtubules and the asters
a structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle.
What happens in prometaphase?
some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes
What happens in interphase?
cell growth and copying of chromosomes in preparation for cell division
What happens in metaphase?
the chromosomes are all lined up at the metaphase plate, the midway point between the spindle's two poles
What is the metaphase plate?
midway point between the spindle's two poles
What happens in anaphase?
sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell
The microtubules shorten by___________ at their kinetochore ends.
What happens in telophase?
genetically identical daughter nuclei for at opposite ends of the cell
Where does cytokinesis occur?
How does cytokinesis occur in animals?
occurs by a process known as cleavage, forming a cleavage furrow
How does cytokinesis occur in plants?
cell plate forms during cytokinesis
Why does the process of cytokinesis differ between plants and animals?
Because plant cell has plant cell walls
Which organisms reproduce by binary fission?
prokaryotes (bacteria and archaea)
How do prokaryotes and eukaryotes differ with respect to their genetic material? (3)
- has one piece of DNA
- circular DNA
- no nucleus
What is binary fission?
chromosome replicates (beginning at origin of replication) and the two daughter chromosomes actively move apart
The eukaryotic cell is regulated by a _________________.
molecular control system
What are the 3 checkpoints in a cell cycle?
- G1 checkpoint
- G2 checkpoint
- M checkpoint
The ___________________ varies with the type of cell.
frequency of cell division
These cell cycle differences result from ______________________.
regulation at the molecular level
How is the cell cycle system regulated?
by both internal and external controls
For many cells what is the most important checkpoint?
What happens if a cell receives a go-ahead signal at the G1 checkpoint?
it will usually complete the S, G2 and M phases and divide.
what happens if a cell does not receive a go-ahead signal at the G1 checkpoint?
it will exit the cycle, switching into a nondividing state called the G0 phase
What is the order of phases in a cell cycle?
What is an example of an internal signal?
an example is that kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase
What is an example of an external signal?
growth factors, which are protein released by certain cells that stimulate other cells to divide
give an example of a growth factor.
PDGF, which stimulates the division of human fibroblast cells in culture
What is cancer?
unregulated cell growth/division
_________ cells do not respond normally to the body's control mechanisms.
Cancer cells may not need growth factors to grow and divide, why? (3)
- they make their own growth factor
- they may convey a growth factor's signal without the presence of the growth factors
- they may have an abnormal cell cycle control system
A normal cell is converted to a cancerous cell by a process called ________________.
Cancer cell cause tumors, what are they?
masse of abnormal cells within otherwise normal tissue
What benign tumor? (2)
- a lump of abnormal cells that remain at the original site
- has not spread yet
What is malignant tumors?
lump of abnormal cells that have invaded surrounding tissues and can metastasize exporting cancer cells to other parts of the body where they may form secondary tumors
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