USABO CORRECT FINALS QUESTIONS AND
ANSWERS SET A+
✔✔protein kinase - ✔✔An enzyme that transfers phosphate groups from ATP to a
protein, thus phosphorylating the protein.
✔✔protein phosphatase - ✔✔An enzyme that removes phosphate groups from
(dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase.
✔✔receptor tyrosine kinase - ✔✔A receptor protein in the plasma membrane, the
cytoplasmic (intracellular) part of which can catalyze the transfer of a phosphate group
from ATP to a tyrosine on another protein. Receptor tyrosine kinases often respond to
the binding of a signaling molecule by dimerizing and then phosphorylating a tyrosine
on the cytoplasmic portion of the other receptor in the dimer. The phosphorylated
tyrosines on the receptors then activate other signal transduction proteins within the
cell.
✔✔scaffolding protein - ✔✔A type of large relay protein to which several other relay
proteins are simultaneously attached, increasing the efficiency of signal transduction.
✔✔second messenger - ✔✔A small, nonprotein, water-soluble molecule or ion, such as
a calcium ion (Ca2+) or cyclic AMP, that relays a signal to a cell's interior in response to
a signaling molecule bound by a signal receptor protein.
✔✔signal transduction - ✔✔The linkage of a mechanical, chemical, or electromagnetic
stimulus to a specific cellular response.
✔✔signal transduction pathway - ✔✔A series of steps linking a mechanical or chemical
stimulus to a specific cellular response.
,✔✔testosterone - ✔✔A steroid hormone required for development of the male
reproductive system, spermatogenesis, and male secondary sex characteristics; the
major androgen in mammals.
✔✔transcription factor - ✔✔A regulatory protein that binds to DNA and affects
transcription of specific genes.
✔✔transduction - ✔✔(1) A type of horizontal gene transfer in which phages (viruses)
carry bacterial DNA from one host cell to another. (2) In cellular communication, the
conversion of a signal from outside the cell to a form that can bring about a specific
cellular response.
✔✔yeast - ✔✔Single-celled fungus that reproduces asexually by binary fission or by the
pinching of small buds off a parent cell; some species exhibit cell fusion between
different mating types.
✔✔actin - ✔✔A globular protein that links into chains, two of which twist helically about
each other, forming microfilaments (actin filaments) in muscle and other kinds of cells.
✔✔anaphase - ✔✔The fourth stage of mitosis, in which the chromatids of each
chromosome have separated and the daughter chromosomes are moving to the poles
of the cell.
✔✔anchorage dependence - ✔✔The requirement that a cell must be attached to a
substratum in order to divide.
✔✔aster - ✔✔A radial array of short microtubules that extends from each centrosome
toward the plasma membrane in an animal cell undergoing mitosis.
✔✔Bacteria - ✔✔One of two prokaryotic domains, the other being Archaea.
✔✔binary fission - ✔✔A method of asexual reproduction by "division in half." In
prokaryotes, binary fission does not involve mitosis; but in single-celled eukaryotes that
undergo binary fission, mitosis is part of the process.
✔✔cell cycle control system - ✔✔A cyclically operating set of molecules in the
eukaryotic cell that both triggers and coordinates key events in the cell cycle.
✔✔cell division - ✔✔The reproduction of cells.
✔✔cell plate - ✔✔A double membrane across the midline of a dividing plant cell,
between which the new cell wall forms during cytokinesis.
,✔✔centromere - ✔✔The specialized region of the chromosome where two sister
chromatids are most closely attached.
✔✔centrosome - ✔✔Structure present in the cytoplasm of animal cells, important during
cell division; functions as a microtubule-organizing center. A centrosome has two
centrioles.
✔✔checkpoint - ✔✔A control point in the cell cycle where stop and go-ahead signals
can regulate the cycle.
✔✔chromatin - ✔✔The complex of DNA and proteins that makes up a eukaryotic
chromosome. When the cell is not dividing, chromatin exists in its dispersed form, as a
mass of very long, thin fibers that are not visible with a light microscope.
✔✔chromosome - ✔✔A cellular structure carrying genetic material, found in the nucleus
of eukaryotic cells. Each chromosome consists of one very long DNA molecule and
associated proteins. (A bacterial chromosome usually consists of a single circular DNA
molecule and associated proteins. It is found in the nucleoid region, which is not
membrane bounded.) See also chromatin.
✔✔cleavage - ✔✔(1) The process of cytokinesis in animal cells, characterized by
pinching of the plasma membrane. (2) The succession of rapid cell divisions without
significant growth during early embryonic development that converts the zygote to a ball
of cells.
✔✔cleavage furrow - ✔✔The first sign of cleavage in an animal cell; a shallow groove in
the cell surface near the old metaphase plate.
✔✔cyclin - ✔✔A cellular protein that occurs in a cyclically fluctuating concentration and
that plays an important role in regulating the cell cycle.
✔✔cyclin-dependent kinase (Cdk) - ✔✔A protein kinase that is active only when
attached to a particular cyclin.
✔✔cytokinesis - ✔✔The division of the cytoplasm to form two separate daughter cells
immediately after mitosis, meiosis I, or meiosis II.
✔✔density-dependent inhibition - ✔✔The phenomenon observed in normal animal cells
that causes them to stop dividing when they come into contact with one another.
✔✔Down syndrome - ✔✔A human genetic disease caused by the presence of an extra
chromosome 21; characterized by mental retardation and heart and respiratory defects.
✔✔G0 phase - ✔✔A nondividing state occupied by cells that have left the cell cycle.
, ✔✔G1 phase - ✔✔The first gap, or growth phase, of the cell cycle, consisting of the
portion of interphase before DNA synthesis begins.
✔✔G2 phase - ✔✔The second gap, or growth phase, of the cell cycle, consisting of the
portion of interphase after DNA synthesis occurs.
✔✔gamete - ✔✔A haploid reproductive cell, such as an egg or sperm. Gametes unite
during sexual reproduction to produce a diploid zygote.
✔✔genome - ✔✔The genetic material of an organism or virus; the complete
complement of an organism's or virus's genes along with its noncoding nucleic acid
sequences.
✔✔growth factor - ✔✔(1) A protein that must be present in the extracellular environment
(culture medium or animal body) for the growth and normal development of certain
types of cells. (2) A local regulator that acts on nearby cells to stimulate cell proliferation
and differentiation.
✔✔interphase - ✔✔The period in the cell cycle when the cell is not dividing. During
interphase, cellular metabolic activity is high, chromosomes and organelles are
duplicated, and cell size may increase. Interphase accounts for 90% of the cell cycle.
✔✔kinetochore - ✔✔A structure of proteins attached to the centromere that links each
sister chromatid to the mitotic spindle.
✔✔malignant tumor - ✔✔A cancerous tumor that is invasive enough to impair the
functions of one or more organs.
✔✔metaphase - ✔✔The third stage of mitosis, in which the spindle is complete and the
chromosomes, attached to microtubules at their kinetochores, are all aligned at the
metaphase plate.
✔✔metaphase plate - ✔✔An imaginary plane midway between the two poles of a cell in
metaphase on which the centromeres of all the duplicated chromosomes are located.
✔✔metastasis - ✔✔The spread of cancer cells to locations distant from their original
site.
✔✔mitosis - ✔✔A process of nuclear division in eukaryotic cells conventionally divided
into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.
Mitosis conserves chromosome number by allocating replicated chromosomes equally
to each of the daughter nuclei.
ANSWERS SET A+
✔✔protein kinase - ✔✔An enzyme that transfers phosphate groups from ATP to a
protein, thus phosphorylating the protein.
✔✔protein phosphatase - ✔✔An enzyme that removes phosphate groups from
(dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase.
✔✔receptor tyrosine kinase - ✔✔A receptor protein in the plasma membrane, the
cytoplasmic (intracellular) part of which can catalyze the transfer of a phosphate group
from ATP to a tyrosine on another protein. Receptor tyrosine kinases often respond to
the binding of a signaling molecule by dimerizing and then phosphorylating a tyrosine
on the cytoplasmic portion of the other receptor in the dimer. The phosphorylated
tyrosines on the receptors then activate other signal transduction proteins within the
cell.
✔✔scaffolding protein - ✔✔A type of large relay protein to which several other relay
proteins are simultaneously attached, increasing the efficiency of signal transduction.
✔✔second messenger - ✔✔A small, nonprotein, water-soluble molecule or ion, such as
a calcium ion (Ca2+) or cyclic AMP, that relays a signal to a cell's interior in response to
a signaling molecule bound by a signal receptor protein.
✔✔signal transduction - ✔✔The linkage of a mechanical, chemical, or electromagnetic
stimulus to a specific cellular response.
✔✔signal transduction pathway - ✔✔A series of steps linking a mechanical or chemical
stimulus to a specific cellular response.
,✔✔testosterone - ✔✔A steroid hormone required for development of the male
reproductive system, spermatogenesis, and male secondary sex characteristics; the
major androgen in mammals.
✔✔transcription factor - ✔✔A regulatory protein that binds to DNA and affects
transcription of specific genes.
✔✔transduction - ✔✔(1) A type of horizontal gene transfer in which phages (viruses)
carry bacterial DNA from one host cell to another. (2) In cellular communication, the
conversion of a signal from outside the cell to a form that can bring about a specific
cellular response.
✔✔yeast - ✔✔Single-celled fungus that reproduces asexually by binary fission or by the
pinching of small buds off a parent cell; some species exhibit cell fusion between
different mating types.
✔✔actin - ✔✔A globular protein that links into chains, two of which twist helically about
each other, forming microfilaments (actin filaments) in muscle and other kinds of cells.
✔✔anaphase - ✔✔The fourth stage of mitosis, in which the chromatids of each
chromosome have separated and the daughter chromosomes are moving to the poles
of the cell.
✔✔anchorage dependence - ✔✔The requirement that a cell must be attached to a
substratum in order to divide.
✔✔aster - ✔✔A radial array of short microtubules that extends from each centrosome
toward the plasma membrane in an animal cell undergoing mitosis.
✔✔Bacteria - ✔✔One of two prokaryotic domains, the other being Archaea.
✔✔binary fission - ✔✔A method of asexual reproduction by "division in half." In
prokaryotes, binary fission does not involve mitosis; but in single-celled eukaryotes that
undergo binary fission, mitosis is part of the process.
✔✔cell cycle control system - ✔✔A cyclically operating set of molecules in the
eukaryotic cell that both triggers and coordinates key events in the cell cycle.
✔✔cell division - ✔✔The reproduction of cells.
✔✔cell plate - ✔✔A double membrane across the midline of a dividing plant cell,
between which the new cell wall forms during cytokinesis.
,✔✔centromere - ✔✔The specialized region of the chromosome where two sister
chromatids are most closely attached.
✔✔centrosome - ✔✔Structure present in the cytoplasm of animal cells, important during
cell division; functions as a microtubule-organizing center. A centrosome has two
centrioles.
✔✔checkpoint - ✔✔A control point in the cell cycle where stop and go-ahead signals
can regulate the cycle.
✔✔chromatin - ✔✔The complex of DNA and proteins that makes up a eukaryotic
chromosome. When the cell is not dividing, chromatin exists in its dispersed form, as a
mass of very long, thin fibers that are not visible with a light microscope.
✔✔chromosome - ✔✔A cellular structure carrying genetic material, found in the nucleus
of eukaryotic cells. Each chromosome consists of one very long DNA molecule and
associated proteins. (A bacterial chromosome usually consists of a single circular DNA
molecule and associated proteins. It is found in the nucleoid region, which is not
membrane bounded.) See also chromatin.
✔✔cleavage - ✔✔(1) The process of cytokinesis in animal cells, characterized by
pinching of the plasma membrane. (2) The succession of rapid cell divisions without
significant growth during early embryonic development that converts the zygote to a ball
of cells.
✔✔cleavage furrow - ✔✔The first sign of cleavage in an animal cell; a shallow groove in
the cell surface near the old metaphase plate.
✔✔cyclin - ✔✔A cellular protein that occurs in a cyclically fluctuating concentration and
that plays an important role in regulating the cell cycle.
✔✔cyclin-dependent kinase (Cdk) - ✔✔A protein kinase that is active only when
attached to a particular cyclin.
✔✔cytokinesis - ✔✔The division of the cytoplasm to form two separate daughter cells
immediately after mitosis, meiosis I, or meiosis II.
✔✔density-dependent inhibition - ✔✔The phenomenon observed in normal animal cells
that causes them to stop dividing when they come into contact with one another.
✔✔Down syndrome - ✔✔A human genetic disease caused by the presence of an extra
chromosome 21; characterized by mental retardation and heart and respiratory defects.
✔✔G0 phase - ✔✔A nondividing state occupied by cells that have left the cell cycle.
, ✔✔G1 phase - ✔✔The first gap, or growth phase, of the cell cycle, consisting of the
portion of interphase before DNA synthesis begins.
✔✔G2 phase - ✔✔The second gap, or growth phase, of the cell cycle, consisting of the
portion of interphase after DNA synthesis occurs.
✔✔gamete - ✔✔A haploid reproductive cell, such as an egg or sperm. Gametes unite
during sexual reproduction to produce a diploid zygote.
✔✔genome - ✔✔The genetic material of an organism or virus; the complete
complement of an organism's or virus's genes along with its noncoding nucleic acid
sequences.
✔✔growth factor - ✔✔(1) A protein that must be present in the extracellular environment
(culture medium or animal body) for the growth and normal development of certain
types of cells. (2) A local regulator that acts on nearby cells to stimulate cell proliferation
and differentiation.
✔✔interphase - ✔✔The period in the cell cycle when the cell is not dividing. During
interphase, cellular metabolic activity is high, chromosomes and organelles are
duplicated, and cell size may increase. Interphase accounts for 90% of the cell cycle.
✔✔kinetochore - ✔✔A structure of proteins attached to the centromere that links each
sister chromatid to the mitotic spindle.
✔✔malignant tumor - ✔✔A cancerous tumor that is invasive enough to impair the
functions of one or more organs.
✔✔metaphase - ✔✔The third stage of mitosis, in which the spindle is complete and the
chromosomes, attached to microtubules at their kinetochores, are all aligned at the
metaphase plate.
✔✔metaphase plate - ✔✔An imaginary plane midway between the two poles of a cell in
metaphase on which the centromeres of all the duplicated chromosomes are located.
✔✔metastasis - ✔✔The spread of cancer cells to locations distant from their original
site.
✔✔mitosis - ✔✔A process of nuclear division in eukaryotic cells conventionally divided
into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.
Mitosis conserves chromosome number by allocating replicated chromosomes equally
to each of the daughter nuclei.
