1.Where do cells arise from?
Cells arise only from preexisting cells.
2.What are the two main stages of the cell cycle?
The cell ycle consists of two broad stages: a growing stage (called interphase) and the actual cell division (called the mitotic phase).
3.What can happen if a person has an extra copy of chromosome 21?
There is a chance that this person might have the Down syndrome.
Five main facts from the reading:
1.Prokaryotes reproduce by binary fission.
2.The large, complex chromosomes of eukaryotes duplicate with each cell division.
3.The cell cycle multiplies cells.
4.Cell division is a continuum of dynamic changes.
5.Cytokinesis differ for plant and animal cells.
Diagram:
This diagram shows an example of binary fission of a prokaryotic cell.
Link: http://www.tutorvista.com/biology/transverse-binary-fission
Summary:
The introduction of the chapter talked about people who are trying to safe different plant species, because they are not very many of these kinds left. It also talked about life cycle, which is the sequence of stages leading from the adults of one generation to the adults of the next. Sperm and egg each carry one set of genetic information - one copy of the organism's genome.Like begets like is an adage that applies only to asexual reproduction, the creation of genetically identical offspring by a single parent, without the participation of sperm and egg. For example an amoeba is an organism which duplicates its chromosomes, the structures that contain most of the organism's DNA. Offspring produced by sexual reproduction generally resemble their parents more closely than they resemble unrelated individuals of the same species, but they are not identical to their parents or to each other. Cells arise only from preexisting cells. The reproduction of cells is called cell division. Prokaryotes reproduce by a type of cell division called binary fission.The large, complex chromosomes of eukaryotes duplicate with each cell division. These cells are more complex and generally much larger than prokaryotic cells, and they have many more genes. Almost all the genes in the cells of humans, and in all other eukaryotes, are found in the cell nucleus, grouped into multiple chromosomes. Most of the time, chromosomes exist as a diffuse mass of long, thin fibers.This material, called chromatin, is a combination of DNA and protein molecules. Before a eukaryotic cell begins to divide, it duplicates all of its chromosomes. The DNA molecule of each chromosome is copied, and new protein molecules attach as needed. The result is that each chromosome now consists of two copies called sister chromatids,w hich contain identical copies of the DNA molecule. Two chromatids are joined together especially tightly at a narrow "waist" called the centromere. The cell cycle multiplies cells. It is an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division into two cells. The cell cycle consists of two broad stages: a growing stage (called interphase), during which the cell roughly doubles everything in its cytoplasm and precisely replicates its chromosomal DNA, and the actual cell division (called the mitotic phase). The mitotic phase is divided into two stages, called mitosis and cytokinesis, although the second stage begins before the first one ends. In mitosis, the nucleus and its contents, including the duplicated chromosomes, divide ad are evenly distributed to form two daughter nuclei. During cytokinesis, the cytoplasm is divided in two. Mitosis is a continuum of changes, but there are five main distinguished stages: prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis differs for plant and animal cells. Anchorage, cell, cell density, and chemical growth factors affect cell division. A growth factor is a protein secreted by certain body cells that stimulates other cells to divide. The effect of a physical factor on cell division is clearly seen in density-dependent inhibition, a phenomenon in which crowded cells stop dividing. Growth factors signal the cell cycle control system. This system is a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle. Growing out of control, cancer cells produce malignant tumors.A tumor is an abnormally growing mass of body cells. If the abnormal cells remin at the original site, the lump is called a benign tumor. In contrast, a malignant tumor can spread into neighboring tissues and other parts of the body, displacing normal tissue and interrupting organ function as it goes. The spread of cancer cells via the circulatory system beyond their original site is called metastasis. In short, mitosis provides for growth, cell replacement, and asexual reproduction. In humans, a typical body cell, called a somatic cell, has 46 chromosomes. They are matched in homologous pairs. X and Y chromosomes are called sex chromosomes. The other 22 pairs of chromosomes are called autosomes. Gametes are the egg and sperm cells, and they have a single set of chromosomes. Any cell with two homologous sets of chromosomes is called a diploid cell. A cell with a single chromosome set is called a haploid cell. Meiosis is a type of cell division that produces haploid gametes in diploid organisms. Mitosis and meiosis have many important similarities and differences. Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring. Homologous chromosomes can carry different versions of genes. Crossing over is an exchange of corresponding segments between two homologous chromosomes. A karyote is a photographic inventory of an individual's chromosomes. If a person has 47 chromosomes, instead of 46, the condition is called trisomy 21. An extra copy of chromosome 21 causes Down syndrome. Accidents during meiosis can alter chromosome number. Abnormal numbers of sex chromosomes do not usually affect survival. New species can arise from errors in cell division. Alternations of chromosome structure can cause birth defects and cancer.
Key Terms:
1.Life cycle - the sequence of stages leading from the adults of one generation to the adults of the next.
2.Asexual reproduction - the creation of genetically identical offspring by a single parent, without the participation of sperm and egg.
3.Cell division - the reproduction of cells.
4.Chromatin - a combination of DNA and protein molecules.
5.Cell cycle - an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division into two cells.
6.Cytokinesis - a process during which the cytoplasm is divided in two.
7.Cleavage furrow - a shallow groove in the cell surface.
8.Growth factor - a protein secreted by certain body cells that stimulates other cells to divide.
9.Tumor - an abnormally growing mass of body cells.
10.Metastasis - the spread of cancer cells via the circulatory system beyond their original site.
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