Every cell in the body goes through a life cycle. Cells grow and divide to replace cells that are lost because of normal wear and tear or injury. Different cells grow and die at different rates. Some cells, such as epithelial<span>epithelialA thin layer of epithelial cells that makes up the outer surfaces of the body (the skin) and lines hollow organs, glands and all passages of the respiratory, digestive, reproductive and urinary systems.</span> cells, reproduce quickly. Other cells, like nerve cells, grow slowly. Both normal cells and cancer cells go through a sequence of steps, or phases, when they form new cells. This is called the cell cycle.
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Answer:
c. A chromosomal mutation can change the total number of chromosomes in the cell.
Explanation:
A gene mutation affects a single gene, and replication error is the main cause of gene mutation. A chromosomal mutation affects one part of chromosome or full chromosome. error in meiosis is the main cause of chromosomal mutation. Both mutations are responsible for a change in DNA. A chromosomal mutation leads to the change in total number of chromosomes in the cell.
The correct answer is d. 8p+; 9n; 10e−
Oxygen exists in three isotopes ¹⁶O, ¹⁷O and ¹⁸O. The atomic number of oxygen is 8. It means its nuclei has 8 protons. The given is oxide⁻² anion. This means it has gained 2 electrons. Thus, oxide anion have 8 protons and 10 (8+2) electrons. The number of neutrons depends on the isotope, in this question mass number is given¹⁷O. The mass number is the sum of the protons and neutrons in the nucleus. Hence, number of neutrons oxide anion will be 17-8 = 9 neutrons.
