A DNA sequence encoding a five-amino acid polypeptide is given below.
...ACGGCAAGATCCCACCCTAATCAGACCGTACCATTCACCTCCT...
...TGCCGTTCTAGGGTGGGATTAGTCTGGCATGGTAAGTGGAGGA...
Give the sequence and polarity of the mRNA encoding the polypeptide.

Verified step by step guidance

1. Step 1: Identify the coding strand of the DNA sequence. The coding strand is the strand that has the same sequence as the mRNA (except thymine (T) in DNA is replaced by uracil (U) in mRNA). In this case, the coding strand is the first strand provided: ...ACGGCAAGATCCCACCCTAATCAGACCGTACCATTCACCTCCT....
2. Step 2: Replace all thymine (T) bases in the coding strand with uracil (U) to convert the DNA sequence into the mRNA sequence. This is because mRNA uses uracil instead of thymine.
3. Step 3: Determine the polarity of the mRNA. mRNA is synthesized in the 5' to 3' direction, so the sequence you generate from the coding strand will have the same polarity (5' to 3').
4. Step 4: Verify the sequence by ensuring that it matches the coding strand (with T replaced by U) and is complementary to the template strand (the second strand provided). The template strand is used during transcription to synthesize the mRNA.
5. Step 5: Write the final mRNA sequence with its polarity explicitly labeled as 5' to 3'. This sequence will encode the five-amino acid polypeptide.

Key Concepts

Transcription

Transcription is the process by which the genetic information encoded in DNA is copied into messenger RNA (mRNA). During transcription, RNA polymerase binds to the DNA at the promoter region and synthesizes a complementary RNA strand by pairing RNA nucleotides with the DNA template strand. This process is crucial for gene expression, as it converts the genetic code into a format that can be translated into proteins.

mRNA Sequence

The mRNA sequence is derived from the DNA template during transcription and consists of codons, which are groups of three nucleotides that correspond to specific amino acids. The mRNA sequence is complementary to the DNA template strand and is synthesized in the 5' to 3' direction. Understanding the mRNA sequence is essential for determining the amino acid sequence of the resulting polypeptide.

Polarity of Nucleic Acids

Nucleic acids, including DNA and RNA, have polarity, which refers to the directionality of their strands. DNA and RNA strands have a 5' end and a 3' end, indicating the orientation of the sugar-phosphate backbone. The polarity is important for processes like transcription and translation, as it determines the direction in which nucleotides are added during synthesis and how the mRNA is read by ribosomes.