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