Question

based on the information provided, which types of adult human cells likely lack active telomerase? select all that apply. brain cells stem cells in the skin stem cells in the bone marrow muscle cells liver cells cancer is a family of hundreds or thousands of distinct diseases, all united by several common characteristics. key among these is that cancer cells grow continuously and in an uncontrolled manner. they create disease because they crowd out normal cells and disrupt the ability of other cells, tissues, and organs to function normally. in many or most cases, cancers originate in cells that have undergone what researchers callreplicative senescence—meaning that they no longer divide. based on the information provided, which statement accurately describes cancer cells? even though cancer cells grow rapidly, they do not compete with normal cells for nutrients, oxygen, and other key resources. eventually, cancer cells die—though only after they have divided many times—due to a lack of telomerase and the adverse effects of chromosome shortening. a hallmark of many cancer cells is active telomerase, even though production of the enzyme had previously been shut down.

Explanation:

Telomerase is an enzyme that adds repetitive sequences (telomeres) to the ends of chromosomes, preventing them from shortening. Stem cells (such as those in the skin and bone marrow) need to divide frequently, so they have active telomerase. Brain cells, muscle cells, and liver cells (in adults) do not divide frequently (or in the case of some neurons, do not divide at all), so they likely lack active telomerase.
For the cancer - cell statement: Cancer cells grow continuously and in an uncontrolled manner. They crowd out normal cells. Telomerase is often re - activated in cancer cells. The first option is wrong because cancer cells do compete with normal cells. The second option is wrong because cancer cells often have active telomerase (so they don't die due to chromosome shortening like normal non - dividing cells). The third option is correct as many cancer cells re - activate telomerase.

Answer:

For the first question (cells lacking active telomerase): brain cells, muscle cells, liver cells.
For the second question (description of cancer cells): A hallmark of many cancer cells is active telomerase, even though production of the enzyme had previously been shut down.