Concept explainers
Interpretation:
A possible template strand (
Concept Introduction:
The first step of the synthesis of proteins using the information in DNA is transcription.
During transcription, the synthesis of messenger RNA (mRNA) from DNA takes place.
Only one DNA strand is needed for RNA synthesis, thus the double helix of DNA unwinds during transcription. The strand used for the RNA synthesis is called the template strand. The other strand (the non-template strand) is called the informational strand and is not involved in the RNA synthesis. The informational strand of DNA is complementary to the template strand.
The informational strand of DNA is complementary to the template strand; meaning the base sequence of the informational strand consists of the complementary base sequence of the template strand.
complementary base pairs:
Adenine pairs with thymine (A−T base pair).
Cytosine pairs with guanine (C−G base pair).
In addition, the direction of the two strands in the same DNA has different directions. Therefore, if the template strand goes from 3' to 5', the informational strand goes from 5' to 3'.
The mRNA synthesized from transcription has a complementary sequence to the DNA template from which it is prepared. Since the informational strand of DNA is complementary to the template strand, the mRNA is an exact copy of the informational strand, the only exception is that the base T present in the informational strand is replaced by U on the RNA strand.
The information needed to prepare a polypeptide is in the mRNA strand. Each sequence of three nucleotides (which is called a triplet or a codon) in the mRNA strand codes for a specific amino acid, except for three triplets: UAA, UAG, and UGA do not correspond to any amino acids and they are called stop codons because they signal the termination of protein synthesis.
Based on the codon sequence of the mRNA strand, the amino acid sequence of the polypeptide strand can be determined.
Transfer RNA (tRNA) brings specific amino acids to add to the synthesizing peptide chain. Each individual tRNA contains an anticodon of three nucleotides that is complementary to the codon in mRNA.
In a polypeptide, the amino acids are bonded via peptide bonds.
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EBK GENERAL, ORGANIC, & BIOLOGICAL CHEM
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