Answer
Deoxyribonucleic acid is the genetic material that is found in nuclei and mitochondria. The molecule exits in the form of a double helix ; the supports are formed of sugars (deoxyribose molecules) and phosphates. The center or rungs of the spiral ladder consists of purine (adenine and guanine) and pyrimidine (thymine and cytosine) bases.
DNA contains genetic information in the form of segments called genes. The genetic information is spelled out in a three base code consisting of codons that specify particular amino acids. Gene expression involves the copying of the DNA sequence of codons( transcription) and the putting of the code into a different language (translation) for expression.
In transcription the DNA double helix molecule unwinds and pulls apart . A single strand of DNA is used as the template that is copied to form a complementary strand of ribonucleic acid -- in this process, messenger RNA(mRNA).
Ribonucleic acid is different from DNA in the following ways:
1. RNA is single stranded, while the DNA molecule is in the form of a double stranded helix
2. In the formation of the complementary RNA strand based on the DNA template, the pyrimidine uracil (U) substitutes for thymine. So the base pairs in RNA are AU ( not AT) and CG .
3. The sugar in RNA is also different from that in DNA. Ribose is the RNA sugar; deoxyribose is the sugar in DNA .
4 . Translation includes transfer of the mRNA information into another code, interpreting it, and applying it to produce products--peptides/proteins.
Work Step by Step
In DNA/gene expression the genetic code in the DNA molecule is first copied by the formation of messenger RNA. There are several types of RNA but the the main types are messenger (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
Messenger RNA is a single stranded RNA which is formed in the nucleus . It is a complementary copy of one of the strands of DNA, but substitutes Uracil for thymine in its base code sequence. These RNA molecules carry the DNA (genetic) information out of the nucleus into the cytoplasm to inform and direct the protein synthetic machinery.
The protein synthetic machinery involves ribosomal RNA (rRNA), ribosomes and transfer RNA (tRNA).
Under the direction of mRNA, t-RNA picks up amino acids as dictated by the genetic code and brings them to the rRNA-ribosome complex where they are attached, assembled in dictated polypeptide sequence and later released into the cytoplasm as polypeptides or proteins.
