(answer b)and synthesis of ribosomal RNAs in the nucleolus (answer c)
should not be directly affected. Laminin binds to integrins on the cell sur-
face to facilitate attachment of cells to the basement membrane (answer d).
71.The answer is e.(Ross and Pawlina, pp 88–91. Kumar, pp 26–32.)DNA
degradation is the hallmark of programmed cell death (apoptosis). Random
DNA degradation, inflammation, and cell and nuclear swelling (answers
a→ c)are involved in necrosis (the response to cell injury or toxins), not
apoptosis. Bax and bcl-2 are members of the bcl-2 family of apoptosis reg-
ulatory proteins. Bax is a proapoptotic member of that protein family and
inhibits the antiapoptotic actions of bcl-2. Bax would be down-regulated
and bcl-2 up-regulated in syndactyly where apoptosis has failed (answer d).
Apoptosis works through several different pathways and ultimately
through the caspases, which induce DNA degradation by endonucleases.
72.The answer is a.(Junqueira, pp 51–54. Ross and Pawlina, p 78.)Triple
A syndrome is an autosomal recessive neuroendocrinological disease
caused by mutations in a gene that encodes the nucleoporin ALADIN, a
component of the nuclear pore complex labeled with the arrows in the
electron micrograph. The immediate effect of mutations in the nucleo-
porins is decreased import of macromolecules from the cytoplasm. Patients
with triple A syndrome have adrenocorticotrophic (ACTH)-resistant
adrenal failure, achalasia (abnormal esophageal motility most often due to
inability of the esophageal sphincter to relax), and alacramia (reduced abil-
ity to produce tears). They also demonstrate neurological symptoms affect-
ing the cranial nerves, autonomic nervous system (Horner’s syndrome and
orthostatic hypotension). Phosphorylation (breakdown) and dephospho-
rylation (reconstitution) of the lamins regulates nuclear envelope stability
during the cell cycle (answers b and c).Condensation of chromosomes
would not be directly affected (answer d) and the nucleus is the site of RNA
synthesis(answer e).
152 Anatomy, Histology, and Cell Biology