CELL CYCLE Flashcards
is the ability of organisms to produce more of their own kind and best distinguishes living organisms from nonliving things.
Cell Division
In ________, the division of one cell reproduces the entire organism.
unicellular organisms
Multicellular eukaryotes depend on cell division for:
- Development from a fertilized cell
- Growth
- Repair
is an integral part of the cell cycle, the life of a cell from formation to its own division.
Cell division
a series of events that take place in a cell leading to its division and duplication of its DNA (DNA replication) to produce two daughter cells.
appears to be driven by specific chemical signals present in the cytoplasm
Cell Cycle
conserves the number of chromosome sets, producing cells that are genetically identical to the parent cell.
Mitosis
reduces the number of chromosome sets from two (diploid) to one (haploid), producing cells that differ genetically from each other and from the parent cell.
Meiosis
constitutes all the DNA in the cell. It can consist of a single DNA molecule or a number of DNA molecules.
Genome
DNA molecules in a cell that is packed.
Chromosomes
a complex of DNA and protein that condenses during cell division.
Chromatin
(nonreproductive cells) - have two sets of chromosomes.
Somatic Cells
(reproductive cells) - have half as many chromosomes as somatic cells.
Gametes
Each duplicated chromosome has two sister chromatids (joined copies of the original chromosome), attached along their lengths by ____.
cohesins
is the narrow “Waist” of the duplicated chromosome, where the two chromatids are most closely attached.
centromere
Eukaryotic cells cell division consists of
Mitosis and cytokinesis.
is the division of the genetic material in the nucleus.
Mitosis
is the division of the cytoplasm.
Cytokinesis
are produced by the variation of cell division called meiosis.
Gametes
yields non-identical daughter cells that have half as many chromosomes as the parent cell.
Meiosis
= nucleus + division
Karyokinesis
= cytoplasm + division
Cytokinesis
The cell cycle consists of
- Mitotic (M) phase (Mitosis and Cytokinesis)
- Interphase (cell growth and copying of chromosomes in preparation for cell division.)
Interphase can be divided into subphases:
- Gap1 phase (“First Gap”)
- S phase (“Synthesis”)
- Gap2 phase (“Second Gap”)
The cell grows during all three phases but the chromosomes are duplicated only during
S phase
The longest mitotic phase
Prophase
The longest phase of the cell cycle
Interphase
structure made of microtubules that control chromosome movement during mitosis.
Mitotic Spindle
the microtubule organizing center where the assembly of spindle microtubules begins.
Centrosome
The centrosome replicates during __________,
interphase
forming two centrosomes that migrate to opposite ends of the cell during __________.
prophase and prometaphase
(a radial array of short microtubules) extends from each centrosome.
aster
During ___, some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes.
prometaphase
are protein complexes associated with centromeres.
Kinetochores
At ___________, the chromosomes are all lined up at the metaphase plate, a plane midway between the spindle’s two poles.
metaphase
cohesins are cleaved
Sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell. The microtubules shorten by depolymerizing at their kinetochore ends
anaphase
cohesins are cleaved by an enzyme called
separase
The eukaryotic cell cycle is regulated by a molecular control system
Cell Cycle Control
cells that manage to escape the usual controls on the cell cycle.
Cancer cells
The sequential events of the cell cycle are directed by a distinct _____________, which is similar to a clock. The clock has specific checkpoints where the cell cycle stops until a “go-ahead” signal is received.
cell cycle control system
most important checkpoint
If a cell receives a go-ahead signal, it will usually complete the S, G2, and M phases and divide
G1 checkpoint
If the cell does not receive the go-ahead signal in g1, it will exit the cycle, switching into a nondividing state called the
G0 phase
Living organisms are distinguished by their ability to reproduce their own kind
true
are the units of heredity and are made up of segments of DNA.
Genes
Genes are passed to the next generation via reproductive cells called
gametes (sperm and eggs)
Most DNA is packaged into _________.
chromosomes
Humans have __chromosomes in their somatic cells, all cells of the body except gametes and their precursors.
46 chromosomes
A gene’s specific position along a chromosome is called the __.
locus
a single individual passes all of its genes to its offspring without the fusion of gametes.
asexual reproduction
is a group of genetically identical individuals from the same parent.
clone
two parents give rise to offspring that have unique combinations of genes inherited from the two parents.
sexual reproduction
Human somatic cells have ___ pairs of chromosomes.
23
is an ordered display of the pairs of chromosomes from a cell.
karyotype
two chromosomes in each pair in karyotype are called
they are the same length and shape and carry genes controlling the same inherited characters.
homologous chromosomes, or homologs
Each pair of homologous chromosomes include one chromosome from each parent.
true
The 46 chromosomes in a human somatic cell are two sets of 23: one from the mother and one from the father.
true
(2n) has two sets of chromosomes. For humans, the __ number is 46 (2n = 46).
diploid cell
contains a single set of chromosomes and is haploid (n).
A gamete (sperm or egg)
For humans, the haploid number is _______.
23
Each set of 23 consists of 22 autosomes and a single-sex chromosome, for humans
true
is the union of gametes (the sperm and the egg).
Fertilization
The fertilized egg is called a ________ and has one set of chromosomes from each parent.
zygote
The ________ produces somatic cells by mitosis and develops into an adult.
zygote
each chromosome pairs with its homolog, and crossing over occur.
X-shaped regions called chiasmata are the sites for crossover.
prophase 1
pairs of homologs line up at the metaphase plate, with one chromosome facing each pole.
Microtubules from one pole are attached to the kinetochore of one of the chromosome of each tetrad.
Microtubules from the other kinetochore of the other chromosome pole are attached.
Metaphase 1
pairs of homologous chromosomes separate.
One chromosome of each pair moves toward opposite poles, guided by the spindle apparatus.
Sister chromatids remain attached at the centromere and move as one unit toward the pole.
Anaphase 1
each half of the cell has a haploid set of chromosomes; each chromosome still consists of two sister chromatids.
Telophase 1
usually occurs simultaneously, forming two haploid daughter cells. The cell then proceeds to meiosis 2 which is similar to mitosis.
Cytokinesis
DNA synthesis
cell cycle
S phase
gap for growth
cell cycle
G phase
mitosis (nuclear division)
cell cycle
M phase
cell performs all of its regular functions and gets ready to divide
Metabolic activity is very high
celll phase
interphase
DNA is duplicated
DNA is in the form of chromatin
celll phase
interphase
Any cell that is going to divide must enter this phase
This is the period before DNA synthesis begins
refers to the gap between cell division and DNA synthesis
Here the cell makes ER, ribosomes, and cytosol to make 2 functional cells
G1
Once all of the organelles have been replicated, the cell enters this phase
For the next 6-8 hours it will replicate its DNA
S PHASE
The goal of replication
is to accurately copy the genetic information in the nucleus so that each daughter cell will have an exact copy of the parental DNA
Before a cell starts dividing, the chromosomes are duplicated
This process produces sister chromatids
EM of human chromosome that has duplicated
S PHASE
are identical pairs of chromosomes.
One inherited from mother and one from father
made up of sister chromatids joined at the centromere
Homologous chromosomes
process of dna replication
dna
enzyme unzips into 2 strands
new bases are added in between strands
are homologous chromosome just one double stranded dna that doubled in size
true
This phase spans the time from the completion of DNA synthesis to the onset of cell division
Following DNA replication, the cell spends about 2-5 hours making proteins prior to entering the M phase
G2 Phase
process that separates the duplicated sister chromatids of the parental cell into 2 nuclei
refers specifically to the division of the nucleus of the cell
M PHASE
MITOSIS
Mitosis is a continuum but biologists distinguish 4 stages
Prophase
Metaphase
Anaphase
Telophase
eukaryotic cell has many more genes than a prokaryotic cell
true
are grouped into multiple chromosomes, found in the nucleus
genes
The orientation of the
division plane is determined by a band of cytoskeletal elements called the
thickening at the cell membrane
preprophase band
nucleus migrates to the middle of the cell and layer of cytoplasm forms in the plane where cell division will occur, to keep nucleus in place
phragmosome
nuclear membrane disintegrates nucleolus disappears
chromosomes condense
mitotic spindle begins to form between centrioles
kinetochores begin to mature and attach to spindle
prophase
kinetochores attach chromosomes
to mitotic spindle and align them along metaphase plate at equator of cell
Metaphase
kinetochore microtubules shorten, separating chromosomes to opposite poles
polar microtubules elongate, preparing cell for cytokinesis
mitosis
Anaphase
cell divides, the sister chromatids separate
Two daughter cells are produced
Each has a complete and identical set of chromosomes
mitosis
Anaphase
cell plate forms, dividing daughter
CYTOKINESIS
chromosomes reach poles of cell kinetochores disappear
polar microtubules continue to elongate, preparing cell for cytokinesis
nuclear membrane re-forms nucleolus reappears
chromosomes decondense
mitosis
Telophase
Similar in many ways to mitosis
Several differences
Occurs only in sex cells
Yields gametes (=eggs & sperms) or spores
Involves 2 cell divisions
Results in 4 haploid cells
Leads to genetic variations
Meiosis
Synapsis and crossing over occur
Prophase I
pairing of homologous chromosomes
Synapsis
exchange of segments of homologous chromosomes
Crossing over
Alignment of pairs of homologous chromosomes at the metaphase plate
Metaphase I
Splitting of the pairs of homologous chromosomes and subsequent movement to opposite poles
Anaphase I
Cytokinesis results to two haploid cells (n)
Telophase I
Areas of homologous chromosomes connect at areas or crossing over
chiasmata
DNA does not double
Stages occur like regular mitosis.
Cytokinesis results to four haploid cells (n)
Meiosis II
Proteins called ______proteins monitor
progression through the cell cycle.
checkpoint
places of dna damage checkpoint
g2
s
g1
places of apoptosis
before mitosis
places of spindle checkpoint
anaphase
Two types of regulatory proteins are involved in cell cycle control
cyclins and cyclin-dependent kinases (Cdks)
proteins produced in synchrony with the cell cycle
regulate passage of the cell through cell cycle checkpoints
cyclins
enzymes that drive the cell cycle
activated only when bound by a cyclin
cyclin-dependent kinases (Cdks)
The activity of a Cdk rises and falls with changesin concentration of its cyclin partner
true
cyclin-Cdk complex that triggers a cell’s passage past the G2 checkpoint into the M phase
MPF (maturation-promoting factor)
the signal for anaphase to proceed is transmitted through
activates the proteins that remove the cohesin holding sister chromatids together
anaphase-promoting complex (APC)
cells will not begin anaphase until all chromosomes are properly attached to the spindle at the metaphase plate
mechanism assures that daughter cells have the correct number of chromosomes
internal signal
But plant cells are anchored in place by the cell walls, so plant cancers never spread far or metastasize to other tissues.
true
is the process of genome doubling that gives rise to organisms with multiple sets of chromosomes.
Polyploidy
Polyploidy that occurs when organisms have more than two sets of chromosomes from the same species
Autoploidy
Polyploidy that Results from hybridization between different species
Allopolyploidy
