16. The right answer is cell plate.
In cytokinesis, we have the formation of a new plant wall: the phragmoplast
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The pre-phase band studied on the previous page determines the zone where the wall separating the two daughter cells will be formed at the mitosis. The first step in this construction is an accumulation of mitochondria and dictyosomes on the chosen site.
The confluence of these Golgi vesicles, in a second stage, will form the pectic middle lamella between the two daughter cells. Some trabeculae of endoplasmic reticulum interposing in places preserve spaces where plasmodesmes will be formed.
It will be left to each cell only to deposit, on both sides, of the pectic lamella the constituent molecules of any vegetal wall.
17. The right answer is Living in a stable environment with little variation.
For asexual reproduction, there is no need for fertilization, and therefore no need for a partner. As a result, there is no genetic mixing, whereas in the case of reproduction, there is a combination of genetic material between two individuals (except for parthenogenesis and the particular case of self-fertilization) and therefore genetic diversity. On the other hand, asexual reproduction is fast and low in energy.
18. The right answer is The cell would not divide.
The spindle poisons act during the division of the cell, when the chromosomes are organized into a spindle, before separating to form two identical daughter cells. These drugs prevent the division from arriving at this last stage.
They represent 2 main classes, all derived from plants: the alkaloids of the periwinkle and the taxanes.
19. The right answer is Sister chromatids align in the middle; cytoplasm pinches in to separate daughter cells
Mitosis consists of dividing a mother cell into two daughter cells. Unlike meiosis, mitosis is unsexed. The phases of mitosis are four in number: Prophase, Metaphase (sister chromatid or sister will pair), Anaphase and Telophase (where there is cytoplasm pinches).
20. The right answer is an infectious, chronic disease.
Cancers are not contagious. Certainly, some cancers are caused by viruses or bacteria that are contagious. For example, human papillomavirus can cause cancer of the cervix, predisposing the cells of infected individuals to become malignant. But this cancer is not due to the spread of tumor cells from one person to another. In the case of Tasmanian devil's disease, the cancer cells themselves are the infectious agents.
21. The right answer is DNA replication
Cancer is a disease characterized by the uncontrolled proliferation of cells, linked to an escape from regulatory mechanisms that ensures the harmonious development of our body.
By multiplying in an uncontrolled way, the cancerous cells give birth to bigger and bigger tumors which develop by invading and destroying the zones which surround them (organs).
22. The right answer is chromatin.
Chromatin is a mass of matter that appears to be stained by light or electron microscopy and corresponds to the entanglement of chromosomes located in the nucleus of eukaryotic cells. Chromatin is composed of DNA and proteins, the histones. During the cell cycle period when the cell does not divide (interphase), chromosomes can not be distinguished individually and are found in chromatin.
23. The right answer is Proto-oncogenes become oncogenes.
A proto-oncogene is a gene normally present in the genome but which, following a transformation (mutation for example), can become a transforming gene, that is to say a gene capable of conferring a cancerous phenotype on a eukaryotic cell. . Proto-oncogenes are often genes that stimulate growth. In contrast, there are tumor suppressor genes, the expression of which tends to slow the growth of cells.
