1. Below is a single strand of DNA. If this sequence were a template during DNA

Question

1. Below is a single strand of DNA. If this sequence were a template during DNA replication, what would the final DNA look like? Show the functional chemical group that is always found at the 5’ and 3’ ends. 5’-GGATCTTATGTTTTATCACCCCAGACTTCTCTTAAAAACATTATTTAGTATGTAGCCTGCA-3’ 2. What is the importance of the functional groups at the 5’ and 3’ end of any DNA? 3. The top strand of DNA shown above is the coding strand. What does an mRNA that results from this whole piece of DNA look like? please answer Q 4,5 4. Show the correctly translated polypeptide that would result from your transcribed mRNA. 5. Identify the functional groups that are found at both ends of the polypeptide.

Explanation / Answer

Please find the answers below:

The sequence of the DNA strand is :

5'-GGATCTTATGTTTTATCACCCCAGACTTCTCTTAAAAACATTATTTAGTATGTAGCCTGCA-3’

Part a: What is the importance of the functional groups at the 5’ and 3’ end of any DNA?

Answer: The functional groups at the 5' and 3' end of any DNA play crucial role in transcription and translation process. The 5' and 3' ends of DNA comprise of specilized consensus sequences. These conserved consesus sequence have special functions. The 5' side of the DNA sequence carry the start site, the promoter and the regulator sites for transcription. The start site is a conserved DNA nucleotide which is utmost required for transcription initiation. The promoter regions is a conserved DNA sequence upstream to the start site which carries consenses sequences such as TATA box, upstream regulators and other which help the RNA polymerase to identify the promoter region and binding site of the DNA. The regulator sequence lies upstream the promoter and helps in maintaining structural integrity and functional expressivity of the DNA by regulating binding of RNA polymerase and substrate-specific expression of the gene.

Part 2: What does an mRNA that results from this whole piece of DNA look like?

Answer: The given DNA strand represents the coding strand of DNA. Thus, the mRNA transcribed from it will be opposite in orientation with complementary seqeunces. Importantly, it can be seen that the start codon i.e. ATG comes a few nucleotides after the 5' end. So the nucleotides before the start codon will not be transcribed. Also, the transcription will stop at either of the stop codons i.e. UAA, UAG or UGA towards the 3' side. Thus, the final mRNA sequence will be:

3' UACAAAAUAG-5'

It can be seen from the above sequence that the start codon is ATG i.e. complementary UAC site on mRNA and the stop codon is UAG on the mRNA. Thus, a very short mRNA will be transcribed from this with only 2 codons.

Part 3:  Show the correctly translated polypeptide that would result from your transcribed mRNA

Answer: The polypeptide that would result from translation of this mRNA would be:

5'-Met-Lys-Lys-3'

Part 4: Identify the functional groups that are found at both ends of the polypeptide.

Answer: The lysine amino acids are small amino acids with the capacity to form hydrogen bonds. Such amino acids normally exist in the termanl sequences which help in acquiring complex torsional structures in the polypeptide such as helical structures. Also methionine represents a leader amino acid which has more role in leading the nascent polypeptide to its target sequence rather than determining the structural stability of the polypeptide.

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