Answer:
Explanation:
Deoxyribonuceic acid (DNA) is the stored form of the genetic material, which contains all the instructions needed for the normal functioning of our body. However, this information encoded in the DNA needs to be expressed in order to be functional. Hence the process of GENE EXPRESSION occurs in two major consecutive steps viz: Transcription and Translation.
Transcription is the process by which the information stored in DNA is copied into a mRNA, which acts as carrier and conveys the information out of the nucleus into the site of protein synthesis (RIBOSOME). Transcription involves making a complementary strand of mRNA from a DNA template in a series of steps. Transcription begins when an enzyme called RNA polymerase binds to the region of a gene called PROMOTER, signalling DNA strand to unwind. The RNA polymerase reads the unwound DNA strand and build the mRNA molecule using complementary base pairs i.e. If RNA polymerase reads Adenine nucleotide in the DNA strand, it adds a Uracil nucleotide etc
N.B: Complementary base pairing rule= A-T (U replaces T in RNA) and G-C.
Translation is the second process of gene expression which occurs in a complex containing ribosomal RNA and other proteins/enzymes, called RIBOSOME. Translation uses the nucleotide sequence in mRNA to synthesize proteins. This process of translation cannot occur without tRNA's.
tRNA or transfer RNA is a special type of RNA molecule, which matches an mRNA codon with the amino acid it encodes. N.B: A codon is group of three nucleotides in the mRNA. Each tRNA contains a set of three nucleotides called ANTICODON, which binds to the complementary codon in the mRNA molecule, hence, carrying the amino acid encoded by the mRNA codon it reads and adds it to the growing polypeptide chain (future protein).
