There are 64 codons and 20 amino acids. which of the following is true? . a. several different codons can specify the same amino acid.. b. each codon specifies a different amino acid.. c. some amino acids have no link to a codon.. d. each amino acid is specified by only one codon..

There are 4 nitrogen used in the construction of codon. Each codon is composed of 3 bases. Hence there are 4^3 or 64 codons available. In this case, we combination is distinguishable from one to another and represents another thread of amino acid. Answer is A.

c. nephron

Explanation: The nephron is the functional unit of the kidney, which actively filters blood and generates urine. The nephron is made of the renal corpuscle and renal tubule. Cortical nephrons are located within the renal cortex, whilst juxtamedullary nephrons are observed inside the renal cortex near the renal medulla.