Does DNA consist of two helical strands with the base on both copied by RNA?
The correct answer and explanation is:
DNA consists of two helical strands, but not both of them are copied by RNA. The two strands of DNA form a double helix, where the strands are held together by complementary base pairs: adenine pairs with thymine, and guanine pairs with cytosine. These base pairs are joined by hydrogen bonds, which provide stability to the DNA structure.
During the process of transcription, only one of the two DNA strands, called the template strand, is copied by RNA. The RNA polymerase enzyme reads this template strand and synthesizes a complementary RNA strand. This RNA strand is an exact copy of the non-template DNA strand, except that thymine is replaced by uracil. The resulting RNA molecule is called messenger RNA (mRNA), which carries the genetic instructions from the DNA to the ribosome for protein synthesis.
The other DNA strand, known as the coding strand, has the same sequence as the mRNA (except for thymine replacing uracil in RNA). However, the coding strand is not directly involved in the RNA synthesis process.
After mRNA is synthesized, it undergoes processes like splicing, capping, and polyadenylation before it is translated into proteins. The mRNA is read in sets of three nucleotides, known as codons, which each correspond to a specific amino acid.
In summary, only one strand of DNA is used as a template for RNA transcription, and it is the mRNA that carries the genetic code to be translated into proteins, not both DNA strands.