3. Which three codons would code for a different amino acid sequence from that coded for by the mRNA base

Question

sequence GGU-CGA-CUG

(1) GGU-AGA-CUG

(2) GGC-CGA-CUA

(3) GGU-CGU-CCG

(4) GGA-CGC-CUC

4. Suppose you knew the makeup of specific proteins in a cell. How would you determine the particular DNA code that coded for them?

3. Three structures are represented in the diagram below.

What is the relationship between these three structures?

(1) DNA is made up of proteins that are synthesized in the cell.

(2) Protein is composed of DNA that is stored in the cell.

(3) DNA controls the production of protein in the cell.

(4) The cell is composed only of DNA and protein.

Answer 1

Question 3: Codons Coding for Different Amino Acid Sequences

To find three codons that would code for a different amino acid sequence from the mRNA base sequence GGU-CGA-CUG, we first need to determine the corresponding amino acids:

1. GGU - Glycine (Gly)
2. CGA - Arginine (Arg)
3. CUG - Leucine (Leu)

Now, we can evaluate the options:

1. GGU-AGA-CUG

   • GGU - Glycine (Gly)
   • AGA - Arginine (Arg)
   • CUG - Leucine (Leu)
   • (Same sequence as the original; NOT different)

2. GGC-CGA-CUA

   • GGC - Glycine (Gly)
   • CGA - Arginine (Arg)
   • CUA - Leucine (Leu)
   • (Same first two; NOT different)

3. GGU-CGU-CCG

   • GGU - Glycine (Gly)
   • CGU - Arginine (Arg) (different from original)
   • CCG - Proline (Pro) (this is different from Leu)
   • (Different sequence; this is an option)

4. GGA-CGC-CUC

   • GGA - Glycine (Gly)
   • CGC - Arginine (Arg) (same as original)
   • CUC - Leucine (Leu) (same as original)
   • (Same sequence as the original; NOT different)

Therefore, only option 3 (GGU-CGU-CCG) is different enough to create a different amino acid sequence.

Question 4: Determining DNA Code from Proteins

To determine the particular DNA code that coded for specific proteins in a cell, you would typically perform the following steps:

1. Identify the Amino Acid Sequence: Begin with the known protein sequences (amino acids).
2. Identify Codons: Using the genetic code, translate the amino acid sequences back into potential mRNA codons.
3. Identify the Corresponding DNA Sequence: After determining the mRNA sequences from the codons, convert the mRNA to the corresponding DNA sequence (note that DNA will have thymine (T) instead of uracil (U)).
4. Use Techniques:
   • Reverse Transcription PCR: Could be used if you have mRNA.
   • Gene Fragmentation and Sequencing: To determine the specific gene sequences.
   • Bioinformatics Analysis: Comparing the known protein sequences with databases to find corresponding genes.

Question 5: Relationship Between Structures

The correct choice is:

(3) DNA controls the production of protein in the cell.

This reflects the central dogma of molecular biology: DNA -> mRNA -> Protein. DNA contains the instructions for synthesizing proteins, and the process of protein synthesis is controlled by the information encoded in the DNA.

Answer 2

You sure?

Answer 3

Let's carefully go through your questions again to ensure accuracy.

Question 3: Alternative Codons

The original mRNA sequence provided is GGU-CGA-CUG. The corresponding amino acids are:

• GGU - Glycine (Gly)
• CGA - Arginine (Arg)
• CUG - Leucine (Leu)

Now examining the options:

1. GGU-AGA-CUG

   • GGU - Glycine (Gly)
   • AGA - Arginine (Arg) (this is a different codon but codes for the same amino acid)
   • CUG - Leucine (Leu)
   • Result: Glycine, Arg, Leu (only one change)

2. GGC-CGA-CUA

   • GGC - Glycine (Gly)
   • CGA - Arginine (Arg)
   • CUA - Leucine (Leu) (this is a different codon but codes for the same amino acid)
   • Result: Glycine, Arg, Leu (only one change)

3. GGU-CGU-CCG

   • GGU - Glycine (Gly)
   • CGU - Arginine (Arg) (this is a different codon but codes for the same amino acid)
   • CCG - Proline (Pro)
   • Result: Gly, Arg, Pro (one change)

4. GGA-CGC-CUC

   • GGA - Glycine (Gly)
   • CGC - Arginine (Arg) (different codon, same amino acid)
   • CUC - Leucine (Leu) (different codon, same amino acid)
   • Result: Gly, Arg, Leu (only one change)

To have a completely different amino acid sequence, at least one amino acid needs to change in ALL codons. The third option GGU-CGU-CCG introduces an amino acid change at the third position, from Leu to Pro, making it a candidate for producing a different sequence overall.

Given this revised examination, I apologize for any confusion earlier. A strict interpretation would lead to identifying options including:

• Option 3 (GGU-CGU-CCG) includes different amino acids compared to the original sequence.

Question 4: Determining DNA from Proteins

To find the DNA code from proteins, the following steps apply:

1. Identify the amino acid sequence.
2. Utilize the genetic code chart to determine possible mRNA sequences.
3. Convert those mRNA sequences back to the corresponding DNA sequences.
4. Employ laboratory techniques, as mentioned, to validate the sequences against known DNA databases.

Question 5: Relationship Between Structures

The relationship between DNA and proteins:

(3) DNA controls the production of protein in the cell is indeed the most accurate statement. It reflects the central dogma of molecular biology: DNA to mRNA to protein synthesis, confirming that DNA holds the instructions necessary for protein production.

Thank you for the opportunity to clarify, and I appreciate your patience! If you have more questions or need further clarification, please let me know!