TRANSCRIPTION&TRANSLATION; WORK SKEET Below is the double-stranded DNA sequence
ID: 192749 • Letter: T
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TRANSCRIPTION&TRANSLATION; WORK SKEET Below is the double-stranded DNA sequence ranscription Start Site S) Terminator (shown in blue) of a portion of a hypothetical yeast genome which happens to contain a very small gene. Transcription starts at the after the promoter (shown in yellow) and proceeds in the direction of the arrow. Transcription stops at the end of the Transcription of a Stant Site SD) promoter 5.) which strand ofDNA toporbottom, is the template strand? The bottovninand 6 Write below the sequence of the mRNA produced from this gene, label the 3' and S' ends 7 Write above the amino acid sequence of the polypeptide produced from this gene; label the N and C termin Mr+-His-Tyr-Leu-Asp. ser-Avg-Leu"st. C 8) ita mutation occurred in which a T/A (top/bottom) base pair was added immediately ather the T/A base pair shown in bold")wite the seuence te mRNA formed below; label te3'and S' ends. Ten wtethe amino acid sequence ofthe polpeptdtwwee N rdcw- 9) What is the name for the type of mutation described in question ss above?Explanation / Answer
5. Since the transcription always takes place in 5'--3' direction and we know that transcription takes place on one of the DNA strand that must be in opposite direction to mRNA.Therefore, this DNA stand is 3'-5' strand.Since transcription takes place on this strand, it is thus called as template strand.I simple words,template strands is repository of information.
6.the sequence of mRNA which is written over there is complemetary to Template DNA strand.In other words ,the base sequence of mRNA is similar to coding strand of DNA except that RNA contains Uracil in place of thymine.The reason for this is that uracil has a high rate of mutation than thymine and as such is not present in DNA.Unlike DNA,mRNA is a transitory molecule and as such Uracil does not cause any concern.Moreover, the regulatory sequences of Template strand ie promoter and terminater are not copied into the mRNA because these are not required for protein synthesis.
7.The mRNA contains information in the form of codons .Each codon is formed of three adjacent bases of mRNA.Each codon carries for information for one specific amino acid eg AUG means Methionine.Basically, the information carried by mRNA is translated or decoded by another RNA called as tRNA.tRNA has a codon recognizing site called as anticodon. Some bases of mRNA on its 5' end donot carry any information for amino acid and form UTR (untranslated region).That is why we see that all the bases of mRNA are not translated into amino acids.Same is true with 3' end of mRNA where we have terminator codons like UAA, UAG and UGA.
7. The first tRNA which visits AUG codon of mRNA carries methionine amino acid.Each amino acid are bonded with 3' end of tRNA through COO group and therefor, the NH2 group is free.When subsequent tRNAs come to decode other codons, the amino acids of these tRNAs are joined together through bonds between coo of one amino acid and NH2 of another. As such the polypeptide chain that is formed has two ends ;one with free NH2 end (NH2 is free, not bonded) called as N-terminal and other with free COO end called as C-terminal.
8. when a base is added in the reading frame of the DNA,the sequence of codons is changed and therefore, the sequence of amino acids in the polypeptide is also changed.This kind of mutation is called as frame shift mutation.
9. Frame shift mutation is so called because when a base is either added or removed from mRNA, new combination of bases occur to form codons at the level of insertion or deletion of base.This results in the total shift in the sequence of codons and hence the name.eg If we have AUGCUC in the mRNA we will have meth-phenyle ala. now if A is introduced in the 5' end of this mRNA we get AAUGCUC in which we have AAU and GCU and C ,so the sequence of codons is changed.
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