ch. 10 cell reproduction Flashcards
how do prokaryotic cells divide?
by binary fission
how do eukaryotic cells divide?
by mitosis or meiosis
what is the result of mitosis?
formation of 2 daughter cells
what forces the cell to divide in binary fission?
formation of a septum
what happens during binary fission?
-circular chromosome replicates, beginning at an origin and proceeding bidirectionally
-new chromosomes move to opposite ends (poles) of the cell
what are chromosomes composed of?
chromatin (complex of DNA and proteins)
what are the two types of chromatin?
heterochromatin and euchromatin
what must happen to chromosomes to allow best sorting and separation?
they must be condensed
what is the nucleosome ?
DNA wrapped around a core of 8 histone proteins spaced 200 nucleotides apart
what does further coiling create?
30nm fiber or solenoid
what holds radial loops of chromatin fiber in place? what are they aided by?
scaffold proteins; condensing proteins
most cells have how many versions of each chromosome?
2
what does diploid mean?
two sets of chromosomes
where does each pair of homologous chromosomes come from?
one from mother and one from father
what are homologous chromosomes?
chromosomes that have similar genes (alleles) at identical locations along the DNA molecule
what are sister chromatids?
replicated chromosomes
where are sister chromatids connected? what connects them?
centromere; cohesion protein
what is mitosis?
cell division in which all of the chromosomes are replicated, followed by a single division done in a manner that creates two identical 2N cells from a single 2N cell
what process is used for somatic cell division?
mitosis
what does mitosis create?
two identical 2N cells
what is somatic cell division?
clonal or multicellular
what are the 5 main phases of the cell cycle?
- G1 (gap phase 1)
- S (synthesis)
- G2 (gap phase 2)
- M (mitosis or meiosis, depending on cell type)
- C (cytokinesis)
what composes interphase?
G1, S phase, and G2
what happens during Sphase?
DNA replication; 2 sister chromatids are produced from each chromosome
what happens during G1?
cell growth
what happens during G2?
chromosomes condense
what is the centromere?
the region of the DNA that sister chromatids share
what holds sister chromatids together at the centromere?
cohesion proteins
where are kinetochore proteins?
attached at the centromere
what do the microtubules attach to?
the kinetochore
what are centrioles and what are their function?
microtubule-organizing centers that replicate and move to each end (pole) of the cell
what are the five stages of mitosis in the correct order?
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
what happens during prophase?
-chromosomes further condense
-centrioles move to each pole
-spindle apparatus is assembled
-nuclear envelope dissolves
what happens during prometaphase?
-chromosomes become attached to the spindle apparatus by their kinetochores
-a second set of microtubules is formed from the poles to each kinetochore
-microtubules begin to pull each chromosome toward the center of the cell
what happens during metaphase?
-microtubules pull the chromosomes to align them at the center of the cell
- sister chromatids line up with centromeres on the metaphase plate (imaginary plane through the center of the cell)
what happens during anaphase?
-removal of cohesin allows the centromeres to separate
-microtubules pull sister chromatids toward the poles
-in anaphase A the kinetochores are pulled toward the poles
-in anaphase B the poles move apart
what happens during anaphase a?
the kinetochores are pulled toward the poles
what happens during anaphase b?
the poles move apart
what happens during telophase?
-spindle apparatus disassembles
-nuclear envelope forms around each set of sister chromatids
-chromosomes begin to uncoil
-nucleolus reappears in each new nucleus
what is cytokinesis?
the cleavage of the cell into halves
what do animals use for cytokinesis?
a cleavage furrow
what do plants use for cytokinesis?
a cell plate
what are cyclins?
proteins produced in synchrony with the cell cycle
what are cyclin-dependent kinases (Cdks)?
enzymes that drive the cell cycle; activated only when bound by a cyclin
what do cyclin dependent kinases activate and how?
activate target proteins by phosphorylation
what happens at the G1/S checkpoint?
cell “decides” to divide
what happens at the G2/M checkpoint?
cell makes a “commitment” to mitosis
what happens at the late metaphase (spindle) checkpoint?
cell ensures that chromosomes are attached to the spindle before dividing
what do growth factor do?
trigger intracellular signals that override cell controls that otherwise inhibit cell division
what is cancer?
a failure of cell cycle control resulting in runaway cell division
what two genes can cause cancer when mutated?
tumor-suppressor genes and proto-oncogenes
what is the function of tumor-suppressor genes?
normally prevent division in cells containing mutations
what is the function of proto-oncogenes?
normally code for growth factors or signal transduction proteins that promote normal cell division
what happens to Proto-oncogenes when mutated?
become oncogenes and cause runaway cell division rather than normal (controlled) cell division (oncogenes can also cause cancer when they are introduced into a new cell (e.g., viral oncogenes))
