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What best distinguishes living things from non living things?
The ability of organisms to reproduce
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What is cell division?
reproduction of cells
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What is the function of cell division? (2)
- for growth and repair
- to reproduce
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Define genome.
all the DNA in a cell
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What are chromosomes?
a structure carrying genetic material(and protein), found in the nucleus of a eukaryotic cell
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How many chromosomes do humans have?
46
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Define somatic cells.
non-productive cells, which have 46 chromosomes (2 sets of 23)
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Define gametes. How many do humans have?
- reproductive cells: sperm and eggs, which have half as many chromosomes as somatic cells
- 23 in humans
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What is homologous? (2)
- same shape
- encodes same gene
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What is cell cycle?
the life of a cell from formation to its own division
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What happens in preparation for cell division?
DNA is replicated and the chromosomes condense
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Define chromatid.
once copy of a duplicated chromosome
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Define centromere.
The part of a chromosome that links sister chromatids
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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
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Which stage is longest in cell division?
Interphase
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What are the five stages to mitosis?
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
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When does cytokinesis get underway?
is well underway by late telophase
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Which cytoskeleton component assists in the movement of chromosomes during cell division?
microtubules
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What is the mitotic spindle?
apparatus of microtubules that controls chromosome movement during mitosis
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What is centrosome?
microtubule organizing center
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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
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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
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what are the 3 things that spindles include?
centrosomes, spindle microtubules and the asters
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Define kinetochore.
a structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle.
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What happens in prometaphase?
some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes
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What happens in interphase?
cell growth and copying of chromosomes in preparation for cell division
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What happens in metaphase?
the chromosomes are all lined up at the metaphase plate, the midway point between the spindle's two poles
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What is the metaphase plate?
midway point between the spindle's two poles
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What happens in anaphase?
sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell
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The microtubules shorten by___________ at their kinetochore ends.
depolymerizing
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What happens in telophase?
genetically identical daughter nuclei for at opposite ends of the cell
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Where does cytokinesis occur?
the cytoplasm
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How does cytokinesis occur in animals?
occurs by a process known as cleavage, forming a cleavage furrow
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How does cytokinesis occur in plants?
cell plate forms during cytokinesis
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Why does the process of cytokinesis differ between plants and animals?
Because plant cell has plant cell walls
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Which organisms reproduce by binary fission?
prokaryotes (bacteria and archaea)
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How do prokaryotes and eukaryotes differ with respect to their genetic material? (3)
- has one piece of DNA
- circular DNA
- no nucleus
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What is binary fission?
chromosome replicates (beginning at origin of replication) and the two daughter chromosomes actively move apart
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The eukaryotic cell is regulated by a _________________.
molecular control system
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What are the 3 checkpoints in a cell cycle?
- G1 checkpoint
- G2 checkpoint
- M checkpoint
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The ___________________ varies with the type of cell.
frequency of cell division
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These cell cycle differences result from ______________________.
regulation at the molecular level
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How is the cell cycle system regulated?
by both internal and external controls
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For many cells what is the most important checkpoint?
G1
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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.
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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
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What is the order of phases in a cell cycle?
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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
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What is an example of an external signal?
growth factors, which are protein released by certain cells that stimulate other cells to divide
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give an example of a growth factor.
PDGF, which stimulates the division of human fibroblast cells in culture
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What is cancer?
unregulated cell growth/division
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_________ cells do not respond normally to the body's control mechanisms.
Cancer
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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
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A normal cell is converted to a cancerous cell by a process called ________________.
Transformation
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Cancer cell cause tumors, what are they?
masse of abnormal cells within otherwise normal tissue
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What benign tumor? (2)
- a lump of abnormal cells that remain at the original site
- has not spread yet
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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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