•Amino acid is activated

•Polypeptide chains are formed

•Ribosomes

Sites of protein synthesis

•Messenger RNA (mRNA) and transfer RNA (tRNA)

Bound to the ribosome in the course of protein synthesis

Responsible for the correct order of amino acids in the growing protein chain

• Protein factors

Mycoplasma 黴漿菌

Paramecium 草履蟲

Euplotes 遊僕蟲屬

Candida 念珠菌屬

•Universality of the code

•Three (UAA, UAG, and UGA) serve as termination signals

•Triplet code

•Nonoverlapping

•Reading frames: Starting points for reading genetic messages

•Open reading frames (ORFs)

•If, on average, a STOP codon appears roughly once per 20 codons, either you have not selected an open reading frame (ORF), or the segment of DNA of interest is unlikely to be a gene, or part of a gene.

A) To sequence entire genomes by determining the order of nucleotides in DNA.

B) To determine the specific amino acids coded by different mRNA codons.

C) To measure the strength of binding between different tRNA molecules and ribosomes.

D) To label amino acids with radioactive isotopes for tracking in cellular processes.

「tRNA 對應正確胺基酸」的配對邏輯，就像一種「額外的密碼系統」，因此稱作 第二遺傳密碼。

•Extra level of proofreading by aminoacyl-tRNA synthetases

•Amino acid

•Aminoacyl-AMP remains bound to the enzyme

•Binding of the correct amino acid is verified by an editing site in the tRNA synthetase

•tRNA

•Specific binding sites exist on tRNAs and are recognized by aminoacyl-tRNA synthetases

•A) Ribosome

•B) Aminoacyl-tRNA synthetase

•C) DNA polymerase

•D) RNA polymerase

•Correct Answer: B) Aminoacyl-tRNA synthetase

Answer:

(A)2^nd, 2^nd

(B)3^rd, 1^st

(C)1^st , 3^rd

(D)2^rd, 1^st