Download Plant Cell mitosis does not produce a cleavage

Chapter 10 Reviewing the Chapter
7) How does plant cell mitosis differ from animal cell mitosis?
The centrosomes in plant cells lack centrioles and spindle pole lacks centrioles and asters while
animal cells do. Cytokinesis proceeds differently in plant and animal cells because of differences in
cell structure. Plant Cell mitosis does not produce a cleavage furrow, but instead
produce a cell plate during telophase
8) Contrast cytokinesis in animal cells and plant cells.
In animal cells, a cleavage furrow, which is an indentation of the membrane between the two
daughter nuclei, forms. The cleavage furrow deepens when a band of actin filaments, called the
contractile ring, slowly forms a circular constriction between the two daughter cells.
The rigid cell wall that surrounds plant cells does not permit cytokinesis by furrowing. Instead, it
involves the building of new cell walls between the daughter cells.
9) List and discuss characteristics of cancer cells that distinguish them from normal cells.
Cancer cells lack differentiation. Cancer cells are not specialized and do not contribute to the
functioning of a tissue. They usually look distinctly abnormal and while normal cells can enter the
cell cycle about 50 times before they are incapable of dividing, cancer cells can enter the cell cycle
repeatedly.
Cancer cells have abnormal nuclei. The nuclei of cancer cells are enlarged and may contain an
abnormal number of chromosomes.
Cancer cells do not under apoptosis. Ordinarily, cells with damaged DNA undergo apoptosis. The
immune system can recognize abnormal cells and trigger apoptosis, which normally prevents tumors
from developing. Cancer cells fail to undergo apoptosis even though they are abnormal cells.
Cancer cells form tumors. Cancer cells have lost all restraint and do not exhibit contact inhibition,
unlike normal cells that stop dividing when they come in contact with a neighbor.
Cancer cells undergo metastasis and angiogenesis. Additional mutations may cause a benign
tumor to become malignant, and spread throughout the body, forming new tumors distant from the
primary tumor. These cells now produce enzymes allowing tumor cells to invade underlying tissues.
Then they travel through the blood and lymph, to start tumors elsewhere. This process is known as
metastasis. Blood vessels supplying nutrients to the tumor cells become insufficient to support the
sudden growth of the tumor. Thus, additional mutations occurring in tumor cells allow them to
direct the growth of new blood vessels into the tumor in a process called angiogenesis.
10)Compare and contrast the functions of proto-oncogenes and tumor suppressor genes in
controlling the cell cycle.
Proto-oncogenes are normal genes that promote progression through the cell cycle. A
stimulus, such as an injury, results in the release of a growth factor that binds to a receptor protein in
the p plasma membrane. This sets in motion a whole series of enzymatic reactions leading to the
activation of genes that promote the cell cycle, both directly and indirectly.
Tumor suppressor genes directly or indirectly inhibit the cell cycle and prevent cells from dividing
uncontrollably. Some tumor suppressor genes prevent progression of the cell cycle when DNA is
damaged. Others may promote apoptosis as a last resort.
11) Describe the prokaryotic chromosome and the process of binary fission.
The prokaryotic chromosome is composed of DNA and a limited number of associated proteins. The
bacterial chromosome appears as an electron-dense, irregularly shaped region called the nucleoid
which is not enclosed by membrane. When stretched out, the chromosome is seen to be a circular
Chapter 10 Reviewing the Chapter
loop. Prokaryotes reproduce asexually by binary fission. Before division takes place, the cell enlarges,
and after DNA replication occurs, there are two chromosomes. These chromosomes attach to a
special plasma membrane site and separate by an elongation of the cell that pulls them apart. During
this period, new plasma membrane and cell wall develop and grow inward to divide the cell. When
the cell is about twice its original length, the new cell wall and plasma membrane for each cell are
complete.
12) Contrast the function of cell division in prokaryotic and eukaryotic cells.
Both binary fission and mitosis ensure that each daughter cell is genetically identical to the parent
cell. Cell division in unicellular organisms produces two new individuals and one parent has
produced identical offspring. In multicellular fungi, plants and animals, cell division is part of the
growth process. Cell division is important in multicellular forms for