Plzz help Which describes a promoter?

a. the first part of an operon that regulates where, when, and to what level a gene is
expressed

b. the part of an operon that, if attached by a repressor protein, suppresses the
expression of a gene

c. a cluster of genes that are expressed or repressed as a group

d. an enzyme that helps DNA unzip prior to transcription

Which plant has a visible leaf modification that will it conserve water in extremely dry environments?

Every compound can be represented by a chemical formula. a chemical formula is the set of symbols showing the elements that make up a compound and their proportions. water’s chemical formula is h 2 2 o. that means a molecule of water contains two atoms of hydrogen and one atom of oxygen chemically bonded. a molecule is a group of two or more atoms bonded together. molecules can range in size from two to thousands of atoms. a molecule of a compound is the smallest unit of that compound. every molecule of water has all the physical and chemical properties of water. that’s because every molecule of water is made of the same elements in the same proportions: two hydrogen atoms and one oxygen! which of the following is a true statement? a every molecule of the same compound will have different properties. b every molecule of a compound has the same proportion of elements. c molecules can be physically separated into smaller units of a compound. d molecules cannot be represented by chemical formulae.

Parasitism could be considered a form of which of these types of relationships? -mutualism -commensalism -predator-prey -mimicry