A practical step-by-step on how to transcribe and translate DNA sequence

DNA transcription and translation are common terms in DNA replication. Therefore, for one to understand and master how to transcribe and translate a particular DNA sequence, one needs to know the meaning of DNA replication, DNA transcription, and DNA translation. DNA replication is defined as the synthesis of daughter DNA from the parental DNA. DNA transcription is the process of synthesizing RNA using the DNA template. DNA translation is the process of synthesizing proteins using the messenger RNA (mRNA) as the template. Additionally, one has to comprehend the roles of transfer RNA (tRNA) and messenger RNA (mRNA) in DNA transcription and translation. mRNA transfers the genetic information from the DNA to the ribosomes, where they identify the sequence of the protein product. On the other hand, tRNA interprets the genetic information carried by the messenger RNA into protein. tRNA acts as the physical link between the protein amino acid sequence and the messenger RNA. tRNA has anticodon and covalent attachment ends. The anticodon creates three base pairs with the mRNA codon while the covalent attachment end attaches to the amino acid that resembles the anticodon sequence.

After knowing the basis of DNA replication, the next step is to determine how a given DNA sequence can be transcribed and translated.

First one has to know the Chargaff''s base pairing rule. According to this rule; in DNA, Adenine(A) pairs with thymine (T) in double bonds while cytosine pairs with the guanine in triple bonds. In RNA, thymine is replaced with the uracil(U). Picture 1 shows how these bonds occur in DNA structure.
Picture 1

Step 1: DNA transcription
Take the strand of the provided DNA sequence and transcribe into the messenger RNA by replacing A with U, T with A, G with C and C with G. The resulting mRNA should be complimentary to the DNA.

Step 2: DNA translation
tRNA reads the genetic information in mRNA in form of codon. 1 codon equals to three base pairs which give one amino acid corresponding to the continuous codon sequence of mRNA.  Codon of specific amino acid is provided in the genetic code table as shown in Picture 2. 
Picture 2


Example:
Transcribe and translate the following sequence of DNA: TTAACGCCA. There is a mutation that resulted in AAA being inserted after G. Predict how this mutation would impact the product of translation. 

  Solutions:
In this problem, we replace T with A, A with U, C with G and G with C to get the following mRNA sequence.

AAUUGCGGU

This mRNA sequence gives three codons(AAU, UGC, and GGU). These codons are then checked on the genetic code table to determine which amino acids they represent. The answers to this question are provided in  Picture 3. 

Picture 3
Mutation introduces additional amino acid (phenylalanine) in the normal sequence of polypeptide of synthesized protein.




By following these steps, you can easily transcribe, and translate any DNA sequence. If there is anything you feel is tackled well you can share in the comment. 

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