Question

Question 3: Transcription and Translation

Below is the beginning of the coding strand of the protein-coding region of the Cdc7 gene in yeast. Note that only the coding strand of the DNA is shown. Please be sure to correctly label the ends of any DNA, RNA or protein sequence written below.

5’ATGACAAGCAAAACGAAGAATATCGATGATATACCTCCAGAAATCAAAGAAGAGATGA TACAGCTCTATCATGATCTACCGGGTATAGAAAATGAATATAAACTCATAGACAAGATC GGTGAGGGAACATTTTCGTCAGTGTATAAAGCCAAAGATATCACTGGGAAAATAATAG3’

A. What is the sequence of the first 10 nucleotides of the template strand?

B. What is the sequence of the first 10 nucleotides of the mRNA?

C. If this is the coding strand, then is transcription going from right to left or left to right on the DNA as shown here?

D. Is the promoter for this gene to the right or left of this sequence?

E. Given that the coding strand is shown above, what are the first 5 amino acids of the protein that is made from this gene?

F. When you are studying this gene, you notice that there is another potential translation start side downstream of the first one. If the second potential start codon were used as the ribosome “start translation” signal, what would be the first 5 amino acids coded for in this gene?

Answer 1

Both the strands (Figure 1)

Q. A. What is the sequence of the first 10 nucleotides of the template strand?

Answer: see the above figure 1

5’ TGCTTGTCAT 3’

or

3’ TACTGTTCGT 5’

Q. B. What is the sequence of the first 10 nucleotides of the mRNA?

Answer:

5’AUGACAAGCA 3’

Q. C. If this is the coding strand, then is transcription going from right to left or left to right on the DNA as shown here?

Answer:

It will be in the same direction as the coding strand (see figure 2 below) that is left to right on the coding DNA as shown in question.

Transcription involves copying a gene's DNA sequence to make an RNA molecule. This is performed by enzymes called RNA polymerases, which link nucleotides to form an RNA strand using a DNA strand as a template. RNA polymerase builds an RNA strand in the 5' to 3' direction, adding each new nucleotide to the 3' end of the strand. RNA polymerase binds to a sequence of DNA called the promoter, found near the beginning of a gene. Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription (using Template Strand).

Figure 2

Q. D. Is the promoter for this gene to the right or left of this sequence?

Answer:

Promoter will always at the beginning of the gene. It means it will be left of the given sequence (see figure 2 above).

Q. E. Given that the coding strand is shown above, what are the first 5 amino acids of the protein that is made from this gene?

Answer:

MTSKTKNIDDIPPEIKEEMIQLYHDLPGIENEYKLIDKIGEGTFSSVYKAKDITGKII

Whole translated sequences are written above. And 1st 5 amino acids are highlighted (MTSKT).

Q. F. When you are studying this gene, you notice that there is another potential translation start side downstream of the first one. If the second potential start codon were used as the ribosome “start translation” signal, what would be the first 5 amino acids coded for in this gene?

Answer

Methionine (M) is specified by the codon ATG (in DNA) or AUG (mRNA) and known as the start codon. the protein sequences of given DNA is written below. The second potential start codon were used as the ribosome “start translation” signal is highlighted with first 5 amino acid start with Methionine (M).

MTSKTKNIDDIPPEIKEEMIQLYHDLPGIENEYKLIDKIGEGTFSSVYKAKDITGKII

So the first 5 amino acid start with second potential start codon are MIQLY