In prokaryotic cells, regulator proteins bind to a section of DNA called a/an A)chromatin
B)repressor***
C)promoter
D)operon
“*** is my answer”

C) Promoter

Explanation:

Gene expression is the process of synthesizing RNA from a gene (transcription), and subsequently, proteins from mRNA (translation). In both prokaryotic and eukaryotic cells, gene expression is controlled at the transcriptional level, which is regulated by certain proteins called transcription factors. Transcription factors are proteins that regulate the synthesis of a protein from a gene.

Transcription factors regulate the progression of transcriptional process by binding to a regulatory region on the DNA sequence about to be transcribed called PROMOTER. The promoter region is a DNA sequence contained in the OPERON. This binding influences the binding of the transcription enzyme, RNA polymerase in order for transcription to start.

you are certainly talking about this picture:

a: is the label of the white square, it is showing the  replication fork, formed by helicase (d) ==> so it is the site of dna separation and replication 

b: is a new dna brand that is following directly the replication fork, so it is continuous ==> built continuously from 5' to 3

c: dna polymerase cannot replicate dna on its own, it needs the of their proteins, and one of them plays the role of a clamp which fixes  the dna with the dna template and increases  the processivity of the enzyme. ==>   stops polymerase from falling off the  template.

d: is the enzyme responsible for forming the replication fork (helicase) ==> unwinds and separates dna into two strands

e: is the delayed strand, it is built  in the opposite sense of the helicase, so dna will be built in fragments ==> built  fragments from 5' to 3 joins

and finally f: is the enzyme that builds  the new dna strand (dna polymerase) ==>   adds nucleotides to make a new dna helix.

credit: gradman555p98x9p

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