A eukaryotic gene typically has all of the following features except:
a) an operator
b) control elements
c) a promoter
d) introns
e) a terminator
A
To answer this question, we need to understand the features of a eukaryotic gene and identify which of the given options is not typically associated with it.
First, let's define a few terms. A gene is a specific sequence of DNA that contains the instructions for making a specific protein or molecule. Eukaryotic genes are found in eukaryotic organisms, which include animals, plants, fungi, and protists. They are structurally more complex than prokaryotic genes found in bacteria and archaea.
Now, let's go through each of the given options to determine which one is not typically associated with a eukaryotic gene:
a) An operator: Operators are DNA sequences found in prokaryotic genes that interact with regulatory proteins to control gene expression. In eukaryotic genes, the concept of an operator is not typically used. Therefore, a eukaryotic gene does not typically have an operator.
b) Control elements: Control elements, also known as enhancers and silencers, are DNA sequences that regulate gene expression by binding specific transcription factors. These control elements are commonly found in eukaryotic genes, allowing for fine-tuning of gene expression.
c) A promoter: The promoter is a DNA sequence found at the beginning of a gene that serves as the binding site for RNA polymerase, the enzyme responsible for initiating transcription. Promoters are present in both prokaryotic and eukaryotic genes, thus making them a characteristic feature of eukaryotic genes.
d) Introns: Introns are non-coding regions within a gene that interrupt the coding sequences (exons). Unlike prokaryotes, eukaryotic genes often contain introns. These non-coding sections are removed during a process called splicing and do not contribute to the final protein product.
e) A terminator: A terminator is a DNA sequence found at the end of a gene that signals the cessation of transcription. It is present in both prokaryotic and eukaryotic genes, making it a typical feature of eukaryotic genes as well.
Based on the explanations above, the answer is a) an operator. A eukaryotic gene typically does not have an operator, whereas the other options (control elements, promoter, introns, and terminator) are all commonly associated with eukaryotic genes.