Unit 3 Target 4: Translation

The given mRNA sequence is CUCAAGUGCUUC. Each set of three nucleotides in mRNA, called a codon, codes for a specific amino acid. By referring to the genetic code chart, we can determine the amino acids coded for by each codon. In this case, the codons are CUC, AAG, UGC, and UUC, which correspond to the amino acids Leucine (Leu), Lysine (Lys), Cysteine (Cys), and Phenylalanine (Phe) respectively. Therefore, the portion of the protein molecule coded for by this mRNA sequence is Leu—Lys—Cys—Phe.

The mRNA sequence GUG-GAG-AGC codes for valine (Val), glutamic acid (Glu), and serine (Ser), respectively. This is because the mRNA codons GUG, GAG, and AGC correspond to the amino acids Val, Glu, and Ser according to the genetic code.

The original mRNA sequence ACU codes for the amino acid Thr. However, due to a mutation, the sequence changes to AUU. AUU codes for the amino acid Ile, which means that Ile will replace Thr in the resulting protein.

The difference in the mRNA sequence between Person A and Person B leads to a change in the corresponding amino acid. In Person A, the codon AUG codes for the amino acid Lysine (Lys), while in Person B, the codon AUG codes for the amino acid Glutamic acid (Glu). This substitution of Lys with Glu is caused by the change in the nucleotide sequence of the mRNA.

UAA is a STOP codon because it signals the end of protein synthesis during translation. When UAA is encountered by the ribosome, it does not code for any amino acid, but instead acts as a signal for the ribosome to stop translating the mRNA and release the newly synthesized protein. This termination codon is one of the three stop codons, along with UAG and UGA, that are responsible for terminating protein synthesis.

During translation, the type of amino acid that is added to the growing polypeptide depends on both the codon on the mRNA and the anticodon on the tRNA to which the amino acid is attached. The codon on the mRNA determines the specific amino acid that needs to be added, while the anticodon on the tRNA ensures that the correct tRNA molecule carrying the corresponding amino acid is brought to the ribosome. This interaction between the codon and anticodon ensures that the correct sequence of amino acids is added to the growing polypeptide chain.

In the genetic code, each amino acid is specified by a sequence of three nucleotides called a codon. Therefore, to specify three amino acids, three codons are needed. Each codon codes for a specific amino acid, and by combining multiple codons, the genetic code can create a sequence of amino acids to form a protein.

There are more codons than there are amino acids, so it is possible for an amino acid to be specified by more than one kind of codon.

During the process of translation, the cell utilizes the information encoded in messenger RNA (mRNA) to synthesize proteins. mRNA is transcribed from DNA in the nucleus and then transported to the ribosomes in the cytoplasm. Ribosomes read the mRNA sequence and use it as a template to assemble amino acids in the correct order, forming a polypeptide chain. This process, known as translation, is essential for protein synthesis and is a crucial step in gene expression.

Translation occurs in the ribosome. The ribosome is responsible for the synthesis of proteins by decoding the information contained in mRNA molecules. It acts as a molecular machine that reads the mRNA sequence and assembles the corresponding amino acids into a polypeptide chain. This process occurs in the cytoplasm of the cell. The nucleus contains the DNA, which serves as the template for mRNA synthesis, but translation itself occurs outside the nucleus in the ribosome. The nucleolus is involved in the production of ribosomes, but not directly in translation.

The 3 base sequence found on a tRNA molecule is called an anticodon. The anticodon is complementary to the codon on the mRNA molecule during translation. It helps in the recognition and binding of the correct amino acid to the tRNA molecule, ensuring that the correct amino acid is added to the growing polypeptide chain. Therefore, the anticodon plays a crucial role in protein synthesis.