The Hayflick limit is a natural limit to the
number of times cells can divide.
size of the population on earth.
number of children born to one set of parents.
life span of a victim of genetic disease.
Question 2Which statement about the immune system is correct?
Males tend to have a stronger immune system than females.
Women tend to have stronger immune systems than do men.
The vulnerability of AIDS patients to diseases that are normally reserved for
young children is evidence of the relation between a weakened immune
system and aging.
The immune system gets stronger throughout life as people are exposed to
more types of invaders.
Question 3When human cells are grown under laboratory conditions that encourage them to grow and divide, cells
from human embryos stop dividing after about 50 divisions.
from children divide more quickly than those of adults.
lose their DNA.
continue to reproduce themselves forever.
Question 4Immune cells manufactured in the thymus gland are
B cells.
C cells.
G cells.
T cells.
Question 5B-cells defend the body against invaders by
invading the bone marrow.
attacking cancer cells.
producing antibodies against bacteria and viruses.
making the circulatory system more efficient.
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