A signal reaches a cell mostly in the form of a signalling molecule binding to a receptor on the cell surface. This binding activates a chain of events that amplifies the signal and transfers it inside the cell. Protein kinases phosphorylate proteins and cause their activation or deactivation, or in general modify their activity. When a signalling molecule binds to a receptor, a cascade is activated and the second messengers, such as cAMP, are synthesized. cAMP molecules activate the protein kinases, which phosphorylate specific proteins and activate them.
Answer:
A mutation in <u>DNA </u>results in a change in <u>RNA </u>that sometimes produces a <u>protein </u>with altered structure and function.
Explanation:
DNA is the hereditary material which causes gene expression in our body by producing protein. The type of protein which is produced by DNA totally depends upon the sequence of nucleotides in the DNA. But, DNA molecule does not produce protein directly. Initially it produces RNA (mRNA, tRNA, rRNA) by the process of transcription, the nucleotides in the RNA are complimentary to those in DNA. In short, the message regarding the structure and composition of the type protein to be produced by DNA is first decoded from DNA in the form of RNA. These RNA molecules then synthesize the protein as per the instructions from DNA by the process of translation.
But, in case a mutation occurs in the DNA which causes a change in it's nucleotide/nucleotides, the protein which will be produced will be different in the structure and function than the protein which was supposed to be synthesized. It happens because, a triplet of nucletiodes in the DNA and hence RNA specifies a particular type of amino acid and several amino acids are joined in a long chain to form polypeptide which ultimately forms protein. But, if any nucleotide in the triplet is changed due to mutation it may change the amino acid and if amino acid will change the protein will also get altered.
