Question

For the peptide sequence (from N to C terminus) Lys-Arg-Ser-Cys-Tyr-Tyr-Trp-His-Lys(KRSCYYWHK), which of the following is the correct coding sequence of the gene encoding this peptide?
A) 3’ - aaa tac ggt tat tat cgt cga cgc aaa- 5’
B) 3’ - aaa cgc agc tgc tat tat tgg cat aaa- 5’
C) 3’ - ttt gtagta gtc gta gca act gcg ctt- 5’
D) 3’ - ttc gcg tca acg ctg ctg att gcg ttc-5’

Answer 1

Hint: A gene is a DNA or RNA sequence that directly codes for functioning product molecules, such as RNA or protein. When there are many functional products with overlapping sections, the union of all overlapping genetic sequences coding for them is used. We use this concept here to find the answers.

Complete answer:
The genetic code is a system of principles that live cells employ to convert information contained in genetic material (nucleotide triplet sequences, or codons) into proteins. The ribosome, which uses transfer RNA (tRNA) molecules to deliver amino acids and read the mRNA three nucleotides at a time, connects proteinogenic amino acids in the order prescribed by messenger RNA (mRNA). All creatures have a genetic code that is quite similar and may be stated in a simple table with 64 items.

There are 61 codons that code for 20 amino acids. Two codons, AAA and AAG, code for lysine. AGG, AGA, CGU, CGC, CGA, and CGG are the six codons that code for arginine. AGU, AGC, UCU, UCC, UCA, and UCG are the six codons that code for serine. UGU and UGC both encode cystine. UAU and UAC endocede tyrosine. A single codon, UGG, is used to encode tryptophan. CAU and CAC are the two codons that code for histidine. As a result, the proper coding sequence for Lys-Arg-Ser-Cys-Tyr-Tyr-Trp-His-Lys is 5' - AAA CAT TGG TAT TAT TGC AGC CGC AAA - 3'. The uracil in mRNA is replaced by thymine in DNA in this process.

Thus the correct answer is option ‘B’.

Note: During protein synthesis, the codons determine which amino acid will be added next. A three-nucleotide codon in a nucleic acid sequence indicates a single amino acid, with few exceptions. The vast majority of genes use a single coding scheme (the RNA codon table). Though there are alternative codes (such as in mitochondria), this approach is commonly referred to as the canonical or conventional genetic code, or simply the genetic code.