Hormones as Control Agents

Hormones are major signaling molecules that can stimulate or inhibit gene activity in target cells. In insect life cycles, ecdysone promotes rapid transcription of genes causing chromosomes to enlarge or form polytene chromsomes such as in salivary glands of midge larvae. They consist of multiple DNA molecules that can produce multiple copies of transcripts

Chromosome puffs are portions of the polytene chromosome in which the DNA has loosened up in response to ecdysone to allow transcription. Translation of transcripts from puffed regions produces protein components of saliva.

In vertebrates, some hormones such as somatotropin which is a growth hormore have widespread effects because most of the body's cells have receptors for it. Whereas, others such as prolactin that stimulates milk production affects only the mammary glands because only they have the receptors.

REVIEW: Hormones may ______ gene transcription in target cells.
a. promote
b. inhibit
c. participate in
d. both a and b

PREVIOUS

NEXT

LECTURE 9 INDEX

MAIN INDEX