A) Step 1 - Transcription : During the processof transcription, the information

Question

A) Step 1 - Transcription: During the processof transcription, the information in the DNA codons of a gene istranscribed into RNA.

Suppose that gene X has the DNA base sequence3’-TACCCTTTAGTAGCCACT-5’.

B) Step 2 - Translation:During protein synthesis at the ribosome, the base sequence of themRNA codons is translated to the amino acid sequence of aprotein.

What is the significance of the first and last codons?What meaning do these codons have for proteinsynthesis?

C) Mutations: A mutation is defined as a changein the base sequence of DNA. This may occur as a“mistake” in DNA replication, for example.

Suppose that during DNA replication, two mutant DNA sequencesare produced as shown below.

Question: For each of the two, you will need to firsttranscribe the mRNA, and then use the genetic code table todetermine the amino acid sequence. Then state whether theprotein sequence changes for each.

Question: Then, explain why a change in aminoacid sequence might affect protein function.

Here is the original sequence, followed by two mutatedsequences, 1 and 2:

Original sequence      3'- TACCCTTTAGTAGCCACT-5’

Mutated sequence 1) 3’-TACGCTTTAGTAGCCATT-5'

Mutated sequence 2) 3’-TAACCTTTACTAGGCACT-5’.

Explanation / Answer

A) RNA SEQUENCE: 5'-AUGGGAAAUCAUCGGUGA-3' B) PROTEIN SEQUENCE: Met - Gly - Asn - His - Arg C) Mutated sequence 1 produces RNA sequence:5'-AUGCGAAAUCAUCGGUAA-3' Mutated protein sequence: Met - Arg - Asn - His -Arg Mutated sequence 2 produces RNA sequence:5'-AUUGGAAAUGAUCCGUGA-3' Mutated protein sequence: Ile - Gly - Asn -Asp - Pro A change in the amino acid sequence affects protein functions.Amino acids contains side chains that determine the overall chargesof a peptide. When charges of amino acid side chain changes, thiswill alter the interactions between the peptide. Thus, the proteinmay be disrupted due to different amino acid mutation.

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