Biology 1 Chapter 12 (Lecture) Flashcards
Cell Cycle
The life of a cell from the time it first is formed from a dividing parent cell until its own division into two cells.
Genome
All of a cells genetic information. The genetic info is in its DNA.
DNA molecules are packaged into…
…Chromosomes.
Chromatin
Eukaryotic chromosomes are made of chromatin which is a complex of DNA and the associated protein molecules.
Genes
The units that specify an organism’s inherited traits. Each single chromosome contains one very long, linear DNA molecule that carries several hundred to a few thousand genes.
Each duplicated chromosomes has two…
Sister Chromatids, each containing an identical DNA molecule. They are initially attached all along their lengths by adhesive protein complexes known as cohesions.
In condensed form, the duplicated chromosome has a narrow “waist” at the…
… Centromere which is a specialized region where the two chromatids are most closely attached. The part of a chromatid on either side of the centromere is called an arm.
Later in the cell division process, the two sister chromatids of each duplicated chromosome separate and move into…
2 new nuclei. Once the sister chromatids separate that are considered individual chromosomes.
Mitosis
The division of the nucleus; whereas cytokinesis is the division of the cytoplasm.
The cell cycle is in 2 phases:
- Mitotic (M) Phase: which includes mitosis and cytokinesis; shortesr part of the cell cycle
-
Interphase: when cell growth occurs and chromosomes are copied
- 90% of cycle is in this phase
- G1 (Gap 1)
- S (Synthesis; Chromosomes are duplicated; DNA replication)
- G2 (Gap 2)
Centrosome
A subcellular region containing materials that function throughout the cell cycle to organize the cell’s microtubules. During interphase in animal cells, a single centrosome replicates forming 2 centrosomes which move apart during prophase as spindle microtubules grow out of them. They continue moving until they are at opposite ends of the cell.
Aster
A radial array of short microtubules that extends from each centrosome.
Kinetochores
A structure of proteins associated with specific sections of chromosomal DNA at the centromere where the spindle microtubules attach.
Metaphase Plate
The imaginary plane midway between the spindles of the two poles where the centromeres of all duplicated chromosomes line up.
Cytokinesis in Animal Cells
Cleavage furrow: a shallow groove in the cell surface near the old metaphase plate.
Cytokinesis in Plant Cells
No cleavage furrow; in the middle of the cell, a cell plate forms which enlarges to form a cell wall between 2 daughter cells.
Binary Fission
Division in Half
- Prokaryotes reproduce by binary fission not mitosis
- Single bacterial chromosome consists of a circular DNA molecule and associated protein
- DNA replicates at origin of replication and produces 2 origins; one origin moves rapidly toward opposite end of cell as chromosome replicates; cell elongates - bacteria 2x orginial size; plasma membrane grown inward dividing parent E. coli cell into two daughter cells
The frequency of cell division varies with…
… Type of cell
What is G0 phase?
When a cell is not dividing.
What controls the cell cycle?
It is driven by specific signaling molecules present in the cytoplasm.
Cell Cycle Control System
A cycle operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle.
There is a loss of cell cycle controls in cancer cells
- Cancer cells do not heed the normal signals that regulate the cell cycle.
- They divide excessively and invade other tissues
- Do not stop dividing when growth factors were depleted
- Transformation- the process that converts a normal cell to a cancer cell.
- If the cell evades destruction, it may proliferate and form a tumor- a mass of abnormal cells within otherware normal tissue.
- Benign Tumor
- Malignant Tumor
Benign Tumor
If abnormal cells in lump remain at original size
Malignant Tumor
Abnormal cells become invasive enough to impair the functions of one or more organs.
- Excessive proliferation
- May have unusual # of chromosomes
- Metabolism may be disabled
- May cease to function in any constructive way
- Changes on cell surface can cause cancer cells to lose attachments to neighboring cell and this allows them to spread into nearby tissues- Metastasis
- May also secrete signal molecules that cause blood vessels to grow toward tumor.
Most body cells are in G0. Cancer cells are…
…Actively dividing. Radiation damages DNA in cancer cells more than in normal cells.
Chemotheraputic Drugs
Are toxic to actively dividing cells are administered through circulatory system. These drugs interfere with specific steps in the cell cycle.
- Drug Taxol: Freezes mitotic spindle- stops actively dividing cells from proceeding past metaphase
- Side effects of chemotherapy are due to drug’s effects on normal cells that divide often.
- Nausea effects on intestinal cells
- Loosing of hair effects on hair follicle cells
- Seseptability of immune system effect on immune system cells
Cellular transformations always involves the alteration of…
Genes that somehow influence the cell cycle control system!!!
How many Sister Chromatids per Chromosomes are there at the beginning of Mitosis?
2
How many Sister Chromatids per Chromosomes are there during G1?
0, All chromsomes
How many Sister Chromatids per Chromosomes are there during G2?
2
Somatic Cells
- Nonreproductive Cells
- Have 2 sets of chromosomes
Gametes
- Reproductive Cells
- Sperm & Eggs
The centromere is a region in which
Chromatids are attached to one another.
What is a chromatid?
A replicated chromsome
What is the name for the special region on a duplicated chromosomes that holds the sister chromatids together?
Centromere
???Starting with a fertilized egg (zygote), a series of five cell divisions would produce am early embryo with how many cells?
32
If there are 20 chromatids in a cell, how many centromeres are there?
10
Which of the following statements is NOT true?
A) Mitosis produces new nuclei with exactly the same chromosomal endowment as the parent nucleus.
B) The mitotic spindles in prokaryotic cells are composed of microtubules
C) Mitosis and cytokinesis are required for asexual reproduction
D) All cells come from a prexisting cell
E) Mitosis may occur without cytokinesis
B
Two centrosomes are arranged at opposite poles of the cell.
Prometaphase
Centrioles begin to move apart in animals cells
Prophase
This is the longest of the mitotic stages
Metaphase
Centromeres uncouple, sister chromatids are separated, and the two new chromosomes move to opposite poles of the cell
Anaphase
If cells in the process of dividing are subjected to colchicine, a drug that interferes with the functioning of the spindle apparatus, at which stage will mitosis be arrested?
Metaphase
A cell containing 92 chromatids at metaphase of mitosis would , at its completion, produce two nuclei containing how many chromosomes?
46
All of the following occur during prophase of mitosis in animal cells except
A) The nucleolus can no longer be seen.
B) The centrioles move toward opposite poles
C) The nuclear envelope disappears
D) The spindle is organized
E) Chromosomes are duplicated
E
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?
20
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
Centrosome
All of the following occur during mitosis except the
A) Formation of a spindle
B) Synthesis of DNA
C) Disappearance of the nucleolus
D) Uncoupling of chromatids at the centromere
B
If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase?
16
Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis the result would be a cell with
2 nuclei
Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants
A cell plate begins to form at telophase, whereas animals a cleavage furrow is initiated at that stage.
How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?
The daughter cells have the same number of chromosomes and the same amount of DNA.
The formation of a cell plate is beginning across the middle of a cell an nuclei are re-forming at opposite ends of the cell. What kind of cell is this?
A plant cell undergoing cytokinesis
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, taxol disrupts microtubule formation by binding to microtubules & accelerating their assembly from the protein procursor, tubulin. Surprisingly, this stops mitosis. Specifically, taxol must affect
The fibers of the mitotic spindle
Which of the following organisms does not reproduce cells by mitosis and cytokinesis?
A) Mushroom
B) Cow
C) Banana tree
D) Bacterium
E) Cockroach
D
Chromosomes first become visible during ______ of mitosis.
Prophase
The correct sequence of steps in the M phase of the cell cycel is
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
During which phases of mitosis are chromosomes composed of two chromatids?
From G2 of interphase through metaphase
The somatic cells derived from a single-celled zygote divide by which process?
Mitosis
Imagine looking through a microscope at a squashed onion root rip. The chromosomes of many of the cells are plainly visible. In some cells, replicated chromosomes are aligned along the center (equator) of the cell. These particular cells are in which stage of mitosis?
Prometaphase
Cells that are in a nondividing state are in which phase?
G0
The “restriction point” occurs here.
G1
Nerve and muscle cells are in this phase
G0
The shortest part of the cell cycle.
M
DNA is replicated at this time of the cell cycle
S
A particular cell has half as much DNA as some of the other cells in a mitotically active tissue. The cell in question is most likely in
G1
One difference between a cancer cell and a normal cell is that
Cancer cells continue to divide even when they are tightly packed together.
