Use the genetic code table in the chapter and the DNA sequence below to answer the following questions:
3'-TACATAAAATAATGGCGTTCTATT-5'
a. What would the mRNA sequence be, based on the provided DNA sequence?
b. What would the corresponding polypeptide sequence be for this DNA sequence?
c. What tRNA anticodon loop would correspond to the third codon of the mRNA?
d. What would the mRNA and polypeptide sequences be if the second adenine in the DNA was deleted?

Verified step by step guidance

1. Step 1: Identify the template strand and determine the mRNA sequence by transcribing the DNA. Since the given DNA sequence is 3' to 5', the mRNA is synthesized in the 5' to 3' direction by complementing each base: A pairs with U, T with A, C with G, and G with C. Write the mRNA sequence accordingly.
2. Step 2: Divide the mRNA sequence into codons (groups of three nucleotides) starting from the 5' end. Use the genetic code table to translate each codon into its corresponding amino acid, forming the polypeptide chain. Remember to identify the start codon (usually AUG) and stop codons.
3. Step 3: Locate the third codon in the mRNA sequence. Determine the tRNA anticodon loop sequence by finding the complementary bases to the mRNA codon, remembering that tRNA anticodons are antiparallel and use U instead of T.
4. Step 4: For the mutation where the second adenine in the DNA is deleted, first remove that nucleotide from the original DNA sequence. Then, repeat the transcription process to get the new mRNA sequence.
5. Step 5: Translate the new mRNA sequence into a polypeptide sequence using the genetic code table. Note that the deletion may cause a frameshift mutation, altering the reading frame and potentially changing the entire amino acid sequence downstream of the deletion.

Key Concepts

Transcription and mRNA Synthesis

Transcription is the process where an mRNA strand is synthesized from a DNA template strand by complementary base pairing. The mRNA sequence is complementary to the DNA template strand and is written in the 5' to 3' direction, replacing thymine (T) with uracil (U). Understanding how to transcribe DNA to mRNA is essential for determining the mRNA sequence from a given DNA strand.

Genetic Code and Translation

The genetic code consists of codons, which are triplets of nucleotides in mRNA that specify particular amino acids. Translation is the process where ribosomes read mRNA codons to assemble the corresponding polypeptide chain. Knowing how to use the genetic code table to convert mRNA codons into amino acids is crucial for predicting the polypeptide sequence.

tRNA Anticodon and Codon-Anticodon Pairing

tRNA molecules have anticodon loops with sequences complementary to mRNA codons, allowing them to bring the correct amino acid during translation. The anticodon pairs antiparallel and complementary to the mRNA codon. Identifying the tRNA anticodon for a specific mRNA codon is key to understanding how amino acids are matched during protein synthesis.