Ch 10 Cell Division
cell cycle
ordered series of events involving cell growth and cell division that produces two new daughter cells
Which molecule is a Cdk inhibitor that is controlled by p53?
p21
Which negative regulatory molecule can trigger cell suicide (apoptosis) if vital cell cycle events do not occur?
p53
A diploid cell contains
pairs of homologous chromosomes
mitotic phase
period of the cell cycle during which duplicated chromosomes are distributed into two nuclei and cytoplasmic contents are divided; includes karyokinesis (mitosis) and cytokinesis
interphase
period of the cell cycle leading up to mitosis; includes G1, S, and G2 phases (the interim period between two consecutive cell divisions
gene
physical and functional unit of heredity, a sequence of DNA that codes for a protein
locus
position of a gene on a chromosome
binary fission
prokaryotic cell division process
Attachment of the mitotic spindle fibers to the kinetochores is a characteristic of which stage of mitosis?
prometaphase
The chromosomes become visible under a light microscope during which stage of mitosis?
prophase
kinetchore
protein structure associated with the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase
condensin
proteins that help sister chromatids coil during prophase
A gene that codes for a positive cell cycle regulator is called a(n) _____.
proto-oncogene.
quiescent
refers to a cell that is performing normal cell functions and has not initiated preparations for cell division
centromere
region at which sister chromatids are bound together; a constricted area in condensed chromosomes
retinoblastoma protein (Rb)
regulatory molecule that exhibits negative effects on the cell cycle by interacting with a transcription factor (E2F)
centriole
rod-like structure constructed of microtubules at the center of each animal cell centrosome
S phase
second, or synthesis, stage of interphase during which DNA replication occurs
tumor suppressor gene
segment of DNA that codes for regulator proteins that prevent the cell from undergoing uncontrolled division
Which of the following events does not occur during some stages of interphase?
seperation of sister chromatids
chromatid
single DNA molecule of two strands of duplicated DNA and associated proteins held together at the centromere
Identical copies of chromatin held together by cohesin at the centromere are called _____.
sister chromatids
metaphase
stage of mitosis during which chromosomes are aligned at the metaphase plate
telophase
stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by a new nuclear envelope
prophase
stage of mitosis during which chromosomes condense and the mitotic spindle begins to form
anaphase
stage of mitosis during which sister chromatids are separated from each other
prometaphase
stage of mitosis during which the nuclear membrane breaks down and mitotic spindle fibers attach to kinetochores
cell plate
structure formed during plant cell cytokinesis by Golgi vesicles, forming a temporary structure (phragmoplast) and fusing at the metaphase plate; ultimately leads to the formation of cell walls that separate the two daughter cells
septum
structure formed in a bacterial cell as a precursor to the separation of the cell into two daughter cells
nucleosome
subunit of chromatin composed of a short length of DNA wrapped around a core of histone proteins
Unpacking of chromosomes and the formation of a new nuclear envelope is a characteristic of which stage of mitosis?
telophase
Which of the following is true regarding daughter cells after meiosis I?
They are haploid
Name the common components of eukaryotic cell division and binary fission.
DNA duplication, segregation of duplicated chromosomes, and division of the cytoplasmic contents.
Which of the following occurs during the S phase of the cell cycle?
DNA synthesis
In eukaryotic cells chromatin is composed of
DNA, and Protein
histone
one of several similar, highly conserved, low molecular weight, basic proteins found in the chromatin of all eukaryotic cells; associates with DNA to form nucleosomes
cell cycle
ordered sequence of events that a cell passes through between one cell division and the next
origin
(also, ORI) region of the prokaryotic chromosome where replication begins (origin of replication)
G1 phse
(also, first gap) first phase of interphase centered on cell growth during mitosis
mitosis
(also, karyokinesis) period of the cell cycle during which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase
G 2 phase
(also, second gap) third phase of interphase during which the cell undergoes final preparations for mitosis
A cell with a diploid number of 24 undergoes meiosis. How many chromosomes are in each daughter cell?
12
Human gametes normally have ________ chromosomes?
23
A buffalo cell has 60 chromosomes. A sperm or egg in a buffalo will have _______ chromosomes
30
How many strands of DNA are there in a human somatic cell at the end of the G2 phase of the cell cycle?
92
Motor proteins require which of the following to move chromosomes within a dividing cell?
ATP
Pairs of homologous chromosomes separate during
Anaphase 1
Describe how the duplicated bacterial chromosomes are distributed into new daughter cells without the direction of the mitotic spindle.
As the chromosome is being duplicated, each origin moves away from the starting point of replication. The chromosomes are attached to the cell membrane via proteins; the growth of the membrane as the cell elongates aids in their movement.
Mutation
Asexual reproduction results in identical offspring unless which of the following occur
What steps are necessary for Cdk to become fully active?
Cdk must bind to a cyclin, and it must be phosphorylated in the correct position to become fully active.
Compare and contrast a human somatic cell to a human gamete.
Human somatic cells have 46 chromosomes: 22 pairs and 2 sex chromosomes that may or may not form a pair. This is the 2n or diploid condition. Human gametes have 23 chromosomes, one each of 23 unique chromosomes, one of which is a sex chromosome. This is the n or haploid condition.
Meiosis produces which of the following?
Sex cells
Briefly describe the events that occur in each phase of interphase.
During G1, the cell increases in size, the genomic DNA is assessed for damage, and the cell stockpiles energy reserves and the components to synthesize DNA. During the S phase, the chromosomes, the centrosomes, and the centrioles (animal cells) duplicate. During the G2 phase, the cell recovers from the S phase, continues to grow, duplicates some organelles, and dismantles other organelles.
a second messenger
Fertilization of an egg cell is signaled by a wave of high Ca2+ concentration starting where the sperm entered the egg to across the entire cell. Ca2+ is acting as
At which of the cell cycle checkpoints do external forces have the greatest influence?
G1 checkpoint
___________ are changes to the order of nucleotides in a segment of DNA that codes for a protein.
Gene mutations
Somatic cells are generated by
Mitosis
Anaphase is associated with
Movement of chromosomes to opposite poles of the cell
mitosis
New growth on the grafted part of a plant arises from
What happens to a cell that undergoes mitosis but not cytokinesis?
One cell with two nuclei
Explain the roles of the positive cell cycle regulators compared to the negative regulators.
Positive cell regulators such as cyclin and Cdk perform tasks that advance the cell cycle to the next stage. Negative regulators such as Rb, p53, and p21 block the progression of the cell cycle until certain events have occurred.
Crossing over occurs during which phase of meiosis?
Prophase 1
Rb is a negative regulator that blocks the cell cycle at the G1 checkpoint until the cell achieves a requisite size. What molecular mechanism does Rb employ to halt the cell cycle?
Rb is active when it is dephosphorylated. In this state, Rb binds to E2F, which is a transcription factor required for the transcription and eventual translation of molecules required for the G1/S transition. E2F cannot transcribe certain genes when it is bound to Rb. As the cell increases in size, Rb becomes phosphorylated, inactivated, and releases E2F. E2F can then promote the transcription of the genes it controls, and the transition proteins will be produced.
List the regulatory mechanisms that might be lost in a cell producing faulty p53.
Regulatory mechanisms that might be lost include monitoring of the quality of the genomic DNA, recruiting of repair enzymes, and the triggering of apoptosis.
Chromosomes are duplicated during what stage of the cell cycle?
S phase
Eukaryotic chromosomes are thousands of times longer than a typical cell. Explain how chromosomes can fit inside a eukaryotic nucleus.
The DNA double helix is wrapped around histone proteins to form structures called nucleosomes. Nucleosomes and the linker DNA in between them are coiled into a 30-nm fiber. During cell division, chromatin is further condensed by packing proteins.
Describe the general conditions that must be met at each of the three main cell cycle checkpoints.
The G1 checkpoint monitors adequate cell growth, the state of the genomic DNA, adequate stores of energy, and materials for S phase. At the G2 checkpoint, DNA is checked to ensure that all chromosomes were duplicated and that there are no mistakes in newly synthesized DNA. Additionally, cell size and energy reserves are evaluated. The M checkpoint confirms the correct attachment of the mitotic spindle fibers to the kinetochores.
What is the relationship between a genome, chromosomes, and genes?
The genome consists of the sum total of an organism's chromosomes. Each chromosome contains hundreds and sometimes thousands of genes, segments of DNA that code for a polypeptide or RNA, and a large amount of DNA with no known function.
motiosis
Triploid of a watermelon grows froma zygote into a multicellular plant through the process of
A zygote is another term for
a fertilized egg
Diploid
a zygote is a ____ cell.
What is the main prerequisite for clearance at the G2 checkpoint?
accurate and complete DNA replication
If the M checkpoint is not cleared, what stage of mitosis will be blocked?
anaphase
Separation of the sister chromatids is a characteristic of which stage of mitosis?
anaphase
mitotic spindle
apparatus composed of microtubules that orchestrates the movement of chromosomes during mitosis
Many of the negative regulator proteins of the cell cycle were discovered in what type of cells?
cancer cells
p21
cell cycle regulatory protein that inhibits the cell cycle; its levels are controlled by p53
p53
cell cycle regulatory protein that regulates cell growth and monitors DNA damage; it halts the progression of the cell cycle in cases of DNA damage and may induce apoptosis
FtsZ proteins direct the formation of a _______ that will eventually form the new cell walls of the daughter cells.
cell plate
haploid
cell, nucleus, or organism containing one set of chromosomes (n)
diploid
cell, nucleus, or organism containing two sets of chromosomes (2n)
The fusing of Golgi vesicles at the metaphase plate of dividing plant cells forms what structure?
cellplate
The mitotic spindles arise from which cell structure?
centrosome
homologous chromosomes
chromosomes of the same morphology with genes in the same location; diploid organisms have pairs of homologous chromosomes (homologs), with each homolog derived from a different parent
cleavage furrow
constriction formed by an actin ring during cytokinesis in animal cells that leads to cytoplasmic division
Which protein is a positive regulator that phosphorylates other proteins when activated?
cyclin-dependent kinase (Cdk)
The process of meiosis begins with
diploid cells and ends with haploid cells
G0 phase
distinct from the G1 phase of interphase; a cell in G0 is not preparing to divide
cytokinesis
division of the cytoplasm following mitosis that forms two daughter cells.
metaphase plate
equatorial plane midway between the two poles of a cell where the chromosomes align during metaphase
An organism's traits are determined by the specific combination of inherited _____.
genes
A major advantage of sexual reproduction over asexual reproduction is
genetic variation of offspring
gamete
haploid reproductive cell or sex cell (sperm, pollen grain, or egg)
The first level of DNA organization in a eukaryotic cell is maintained by which molecule?
histone
DNA replicates during which phase of meiosis?
interphase
Which eukaryotic cell cycle event is missing in binary fission?
karyokinesis
cell cycle checkpoint
mechanism that monitors the preparedness of a eukaryotic cell to advance through the various cell cycle stages
During metaphase I and II chromosomes line up along the
metaphase plate
karyokinesis
mitotic nuclear division
oncogene
mutated version of a normal gene involved in the positive regulation of the cell cycle
proto-oncogene
normal gene that when mutated becomes an oncogene
A mutated gene that codes for an altered version of Cdk that is active in the absence of cyclin is a(n) _____.
oncogene.
cyclin-dependent kinase
one of a group of protein kinases that helps to regulate the cell cycle when bound to cyclin; it functions to phosphorylate other proteins that are either activated or inactivated by phosphorylation
cyclin
one of a group of proteins that act in conjunction with cyclin-dependent kinases to help regulate the cell cycle by phosphorylating key proteins; the concentrations of cyclins fluctuate throughout the cell cycle
genome
total genetic information of a cell or organism
A diploid cell has_______ the number of chromosomes as a haploid cell.
twice
