Where are promoters usually located?

a. upstream of the start site

b. downstream of the start site

c. near nucleotide +25

d. near the hairpin loop

e. downstream of the terminator

A. Upstream of the start site

Explanation:

Promoters are the specific DNA sequences that serve as the binding site for the enzyme RNA polymerase and thereby serve in the initiation of the process of transcription. Promoters are mostly present upstream of the start site (towards the 5' end) of a gene and direct the transcription of adjacent segments of DNA. For example, the promoter region in E. coli extends between positions -70 and + 30 and have consensus sequences as -10 and -35 regions. Promoters have specific sequences that determine the efficiency with which an RNA polymerase binds to them.

stratosphere: as the altitude increases, the air temperature increases. the stratosphere has a layer of ozone, called the ozone layer. this layer absorbs most of the ultraviolet radiation from sunlight. this results in the stratosphere being warmer.

answer: tributaries flow into rivers.

wetland is a biome that develops when the water gets accumulated in a land exhibiting a huge depression. these form either seasonally or permanently. the water in the wetland comes from rivers, lakes, ocean, flood, rain or other sources. the wetlands includes mangroves, marshes and peatland.

tributaries flow into the rivers develops a wetland because such water will get deposited in the depression and will restrict the original flow of tributary water. hence, water with low drainage current combines with the river water.