Questions: How many different amino acids are usually there to choose from when assembling a protein? 10 20 64 5 50

The answer is the second one (20): There are 20 different amino acids usually available to choose from when assembling a protein.

Explanation for each option:

1. 10: This is incorrect. There are more than 10 amino acids involved in protein synthesis.

2. 20: This is correct. Proteins are typically made from 20 standard amino acids, which are encoded by the genetic code.

3. 64: This is incorrect. While there are 64 possible codons in the genetic code, they code for only 20 amino acids (plus stop signals).

4. 5: This is incorrect. There are more than 5 amino acids involved in protein synthesis.

5. 50: This is incorrect. There are 20 standard amino acids used in protein synthesis, not 50.

In summary, the correct answer is 20, as there are 20 standard amino acids used in the assembly of proteins.