Antisense DNA Strand Into The MRNA Strand Gene Expression Lab Report

I’m working on a Biology exercise and need support.

 

I have attached the genetic codes list and the worksheet.

Transcribe the “gene” at the top of the worksheet using the genetic code provided in the handout or the one in your textbook. Write your transcribed mRNA molecule directly underneath the “gene” on your worksheet in large letters (so you have room to translate underneath it). Transcribe the gene using complementary base-pairing rules and write the correct mRNA (with 5′ and 3′ labels as directed) below the gene. Make sure your RNA nucleotides line up under each DNA nucleotide and that your mRNA contains U, not T when pairing with A. Label this new mRNA with a 5′ on the left side and the 3′ on the right side because your DNA gene was shown 3′ to 5′ and all nucleic acids pair up in an anti-parallel (opposing directions) way.

Step 4: Use the genetic code key to translate your mRNA. If you transcribed correctly, the first 3 nucleotides on your mRNA should be A-U-G, which translates (using the genetic code) to the amino acid Methionine (often abbreviated Met or just “M”). This A-U-G is also the start codon that tells you to get started translating. For each amino acid, write down only the one-letter abbreviation (so “M” for methionine).

PAY CAREFUL ATTENTION: The first letter is NOT always the correct one-letter abbreviation because some amino acids start with the same letter. For example, because glycine’s one-letter abbreviation is “G”, glutamate’s one-letter abbreviation cannot be “G” so they made it “E” instead!

Step 5: Continue translating until you encounter a STOP codon (see genetic code key for which codons tell you to stop). When you encounter the stop codon, immediately stop translating even if there are more nucleotides in your mRNA after that stop. The stop codon signals to the cell that translation is over and the finished protein gets released to do its job. Make sure you have written your translation using the one-letter abbreviations, not the 3-letter abbreviations (i.e. write “M” for methionine, not “Met”).

If you did the translation correctly, your finished “protein” written in the one-letter abbreviations should spell out an actual English word that begins with the letter M (since all translations begin with the M encoded by the start codon).

Once you’re sure you translated the original gene correctly, we’re going to see what happens if we mutate the gene by making just one single nucleotide change in our DNA.

Step 6: The next section of your worksheet provides you with the SAME gene after it has been exposed to UV rays from too much sunlight. Your cells failed to repair all the DNA damage caused by the UV rays, so this gene now has a single point mutation (highlighted in bold). Transcribe this mutated version of the gene to make the new version of the mRNA that your cells will make from now on.

Step 7: Translate this new, mutated gene’s mRNA to see what effect the mutation had on your protein. Remember to write the translation using the one-letter abbreviations for each amino acid. Does it still spell out an actual English word? Is it the same word?

Step 8: Of the effects caused by “point mutations” in your DNA (single or a couple nucleotides being changed), proteins can exhibit: silent mutations, missense mutations, nonsense mutations and frameshift mutations. Which type of protein effect did this mutation cause? The 3rd section of your worksheet is the original gene again, but this time with a different mutation (highlighted in bold again).

Step 6: Transcribe this next mutated version of the gene to make another different version of the mRNA.