In biology, the strain is a low-level taxonomic rank used in different contexts:
In microbiology, a strain is a part of a bacterial species different from other bacteria of the same species by a minor but identifiable difference. Strains are often created in the laboratory by mutagenesis existing strains or wild-type examples of bacterial species.
In zoology, a strain corresponds to an individual or group of individuals who are at the origin of a line of descendants, sometimes called the holotype, paratypes, etc. A strain is a population of organisms that descends from a single organism or pure isolate culture. Strains of the same species may differ slightly from each other in many respects.
A strain thus consists of a group of organisms of the same species possessing certain differential traits based on their relationship; either they come from the same region, as the same watershed of a river, or they are the fruit of a particular breeding program (exists as a whole interbreeding without introductions from external sources).
It began 3.5 billion years ago
Transcription factors are necessary for an initiation of transcription at a regulated gene but not sufficient.
Transcription is the first step of gene expression in which DNA molecule is copied (transcribed) into RNA (mRNA) by RNA polymerase. The process of transcription is divided into three phases:
1. Initiation
• RNA polymerase with transcriptional factors bind to gene promoter Transcription factors can enhance the interaction between RNA polymerase and a DNA sequence- promoter, encouraging the expression of the gene. Such transcription factors are called activators. Otherwise, when the gene expression is inhibited, factors are called repressors and they bind to sequence –operator.
• RNA polymerase unwinds DNA double helix (transcription bubble is formed)
2. Elongation
• RNA polymerases adds nucleotides complementary to DNA
3. Termination
• RNA polymerase gets to stop codon (transcribes a sequence of DNA known as a terminator)
• Formed complementary RNA strand is released from DNA-RNA complex
Answer:
The answer is the second one so B.)
Explanation:
