Exam 2: Chapter 12 (The Cell Cycle)
Tissue renewal
These dividing bone marrow cells will give rise to new blood cells (LM)
Binary fission
"division in half" refers to this process and to the asexual reproduction of single-cells eukaryotes-mitosis is part of the process. -doubles its size and then divides into two cells. -prokaryotes, this does not involve mitosis
somatic cells
(All body cells except the reproductive cells) Contain 46 chromosomes, made up of two sets of 23, one set inherited from each parent. 18 in cabbage 48 chimpanzees 56 elephants 90 in hedgehogs 148 in one species of alga
Gametes
(reproductive cells) such as sperm and eggs- have half as many chromosomes as somatic cells; in our example, human gametes have one set of 23 chromosomes.
Mitotic spindle
-Begins to form in the cytoplasm during prophase -Consists of fibers made of microtubules and associated proteins -When the mitotic spindle assembles, the other microtubules of the cytoskeleton partially disassemble, providing the material used to construct the spindle
Telophase
-Fifth and final stage of mitosis -Daughter nuclei are forming -Cytokinesis has typically begun *Two daughter nuclei form in the cell. Nuclear envelopes arise from the fragments of the parent cell's nuclear envelope and other portions of the endomembrane system *Nucleoli reappear *The chromosomes become less condensed *Any remaining spindle microtubules are depolymerized *Mitosis, the division of one nucleus into two genetically identical nuclei, is now complete
Prophase
-First stage of mitosis - Chromatin condenses into discrete chromosomes visible with a light microscope, -the mitotic spindle begins to form -the nucleolus disappears but the nucleus remains intact *The chromatin fibers become more tightly coiled, condensing into discrete chromosomes observable with a light microscope *The nucleoli disappear *Each duplicated chromosome appears as two identical sister chromatids joined at their centromeres and, often, all along their arms by cohesions, resulting in sister chromatid cohesion *The mitotic spindle (named for its shape) begins to from. It is composed of the centrosomes and the microtubules that extend from them. The radial arrays of shorter microtubules that extend from the centrosomes are called asters *The centrosomes move away from each other, propelled partly by the lengthening microtubules between them
Anaphase
-Forth stage of mitosis -Chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell *Anaphase is the shortest stage of mitosis, often lasting only a few minutes *Anaphase begins when the cohesion proteins are cleaved. This allows the two sister chromatids of each pair to part suddenly. Each chromatid thus becomes an independent chromosome *The two new daughter chromosomes begin moving toward opposite ends of the cell at their kinetochore microtubules shorten. Because these microtubules are attached at the centromere region, the centromeres are pulled ahead of the arms, moving at a rate of about 1 micrometer/meter *The cell elongates as the non-kinetochore microtubules lengthen *By the end of anaphase, the two ends of the cell have identical- and complete-collections of chromosomes
Prometaphase
-Second stage of mitosis -Nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes *The nuclear envelope fragments *The microtubules extending from each centrosome can now invade the nuclear area *The chromosomes have become even more condensed *A kinetochore, a specialized protein structure, has now formed at the centromere of each chromatid *Some of the microtubules attach to the kinetochores, becoming "kinetochore microtubules" which jerk the chromosomes back and forth *Non-kinetochore microtubules interact with those from oppose pole of the spindle, lengthening the cell
G2 phase ("second gap")
-The second gap, or growth phase, of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs -Metabolic activity, growth, and preparation for cell division *A nuclear envelope encloses the nucleus *The nucleus contains one or more nucleoli *Two centrosomes have formed by duplication of a single centrosome. Centrosomes are regions in animal cells that organize the microtubules of the spindle. Each centrosome contains two centrioles *Chromosomes, duplicated during 5 phase, cannot be seen individually because they have not yet condensed
Metaphase
-Third stage of mitosis -The spindle is complete and the chromosomes -Attached to microtubules at their kinetochores -All aligned at the metaphase plate *The centrosomes are not at opposite poles of the cell *The chromosomes have all arrived at the metaphase plate, a plane that is equidistant between the spindle's two poles. The chromosomes' centromeres lie at the metaphase plate *For each chromosome, the kinetochore of the sister chromatids are attached to kinetochore microtubules coming from opposite poles
Eukaryotic genome
-multiple linear chromosomes-enormous in length
Chromosome duplication and distribution during cell division
1) One of the multiple chromosomes in the eukaryotic cell is represented here, not yet duplicated. At this stage, it is a long, thin chromatin fiber containing one DNA molecule and associated proteins. (for simplicity, the chromosome is shown in condensed form, and the nuclear envelope is not shown 2) Once duplicated, a chromosome consists of two sister chromatids connected along their entire lengths by sister chromatid cohesion. Each chromatid contains a copy of the DNA molecule 3) Molecular and mechanical processes separate the sister chromatids into two chromosomes and distribute them to two daughter cells
Bacterial cell division by binary fission
1- Chromosome replication begins at the origin. Soon after, one copy of the origin moves rapidly toward the other end of the cell by a mechanism involving an actin-like protein 2- Replication continues. One copy of the origin is now at each end of the cell. Meanwhile, the cell elongates. 3- Replication finishes. The plasma membrane is pinched inward by a tubulin-like protein, and a new cell wall is deposited 4- Two daughter cells result
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
A chicken has 78 chromosomes in its somatic cells. How many chromosomes did the chicken inherit from each parent? How many chromosomes are in each of the chicken's gametes? How many chromosomes will be in each somatic cell of the chicken's offspring?
39; 39; 78
Sister chromatids
Identical copies of a chromosome; full sets of these are created during the S subphase of interphase. Attached all along their lengths by protein complexes called cohesins
Malignant tumor
A cancerous tumor containing cells that have significant genetic and cellular changes and are capable of invading and surviving new site. Malignant tumors can impair the functions of one or more organs
Genome
A cell's DNA- genetic information
Cyclin
A cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle
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
Benign tumor
A mass of abnormal cell with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and generally remain at the site of the tumor's origin
Cyclin-dependent kinases
A protein kinase that is active only when attached to a particular cyclin
How can a protein outside the cell cause events to happen inside the cell?
A protein outside the cell can bind to a receptor protein on the cell surface, causing it to change shape and sending a signal inside the cell.
Centromere
A regions made up of repetitive sequences in the chromosomal DNA where the chromatid is attached most closely to its sister chromatid Attachment is mediated by proteins that recognize and bind to the centromeric DNA; other bound proteins condense the DNA, giving the duplicated chromosome a narrow "waist"
Meiosis
A variation of cell division, which yields daughter cells with only one set of chromosomes, half as many chromosomes as the parent cells
asexual reproduction
An amoeba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism (LM)
Arm of the chromatid
An unduplicated chromosome has a single centromere, distinguished by the proteins that bind there. and two arms
Chromatin
Clusters of DNA, RNA, and proteins in the nucleus of a cell
Cell plate
During telophase, vesicles derived from the golgi apparatus move along microtubules to the middle of the cell where they coalesce and produce..
Fertilization
Fuses two gametes together ands the chromosome number to 46 (two sets)
Checkpoint
In the cell cycle is a control point where stop and go-ahead signals can regulate the cycle. -Found in G1, G2, and M phases
Which of the following statements best describes microtubules
Microtubules are made up of subunits of tubulin, and are structures along which substances are transported in the cell
What is the best description of the structure of a chromosome in the nucleus of a non-dividing cell
One long DNA molecule, associated with many proteins
What effect does phosphorylating a protein have on that protein
Phosphorylation changes the shape of the protein, most often activating it.
Cytokinesis
The cell divides into two daughter cells, genetically identical to each other and to the parent cell The division of the cytoplasm, producing two daughter cells. Each daughter cell can start a new cell cycle *The division of the cytoplasm is usually well under way by late telophase, so the two daughter cells appear shortly after the end of mitosis *In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinched the cell in two.
Interphase
The cell grows; in preparation for cell division, the chromosomes are duplicated, with the genetic material (DNA) copied precisely. 90% of the cycle Divided into 3 phases: G1 phase ("first gap"), the S phase ("synthesis"), and the G2 phase ("second gap") *"Gaps" are a false assumption thinking the cells are inactive- these phases show intense metabolic activity and growth throughout.*
Metaphase plate
The centromeres of all the duplicated chromosomes are on a plane midway between the spindle's two poles. -Imaginary plate rather than an actual cellular structure
Mitosis
The chromosome copes are separated form each other and moved to opposite ends of the cell. The division of the genetic material in the nucleus Distribution of chromosomes into two daughter nuclei
G1 phase ("first gap")
The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins. -Metabolic activity and growth
Cleavage furrow
The first sign of cleavage in an animal cell; a shallow groove around the cell in the cell surface near the old metaphase plate
Mitotic (M) phase
The phase of the cell that includes mitosis and cytokinesis. The shortest part of the cell cycle
Cell division
The reproduction of cells
Metastasis
The spread of cancer cells to locations distant from their original site
S phase ("synthesis")
The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated -Metabolic activity, growth, and DNA synthesis
Growth and Development
This micrograph shows a sand dollar embryo shortly after the fertilized egg divided, forming two cells (LM)
Kinetochore
a structure made up of proteins that have assembled on specific sections of DNA at each centromere -during prometaphase, some of the spindle microtubules attach to the kinetochores; these are called kinetochore microtubules
Eukaryotic chromosomes
have linear DNA molecules associated with a large amount of protein
prokaryotic genome
often consists of a single DNA molecule
cell cycle
the life of a cell from the time it is first formed during division of a parent cell until its own division into two daughter cells
Chromosomes
threadlike structures made of DNA molecules that contain the genes
