Genetic Code

Overview

The genetic code is a set of rules by which the sequence of nucleotides in DNA or RNA determines the sequence of amino acids in proteins. It is composed of triplets of nucleotides called codons, where each codon specifies a particular amino acid or a stop signal for protein synthesis. There are 64 codons in total, with 61 coding for amino acids and 3 functioning as stop codons (UAA, UAG, UGA). The code is nearly universal across all organisms and is redundant, meaning some amino acids are specified by more than one codon. The start codon AUG, which codes for methionine, signals the initiation of translation. This universal nature of the genetic code allows the transfer of genes between different organisms for scientific and medical purposes.

Questions and Answers

1. What is the genetic code?

   The genetic code is the set of rules that defines how the sequence of nucleotides in DNA or RNA is translated into the sequence of amino acids in a protein.

2. What is a codon?

   A codon is a sequence of three nucleotides in mRNA that specifies a particular amino acid or a stop signal during protein synthesis.

3. What is the function of the start codon?

   The start codon (AUG) signals the beginning of translation and codes for the amino acid methionine.

4. What are stop codons, and how many are there?

   Stop codons (UAA, UAG, and UGA) signal the end of translation and do not code for any amino acid. There are three stop codons.

5. What does it mean that the genetic code is redundant?

   The genetic code is redundant because multiple codons can specify the same amino acid, providing a safeguard against some mutations.

Multiple-Choice Questions

1. How many codons are in the genetic code?

   a) 16
   b) 32
   c) 64
   d) 128
   Answer: c) 64

2. What does the start codon AUG code for?

   a) Valine
   b) Methionine
   c) Arginine
   d) Tryptophan
   Answer: b) Methionine

3. Which of the following is a stop codon?

   a) AUG
   b) UGA
   c) AAA
   d) GCU
   Answer: b) UGA

4. What does it mean when the genetic code is described as "redundant"?

   a) Each codon codes for multiple amino acids.
   b) Some amino acids are coded by more than one codon.
   c) Codons are universal in all organisms.
   d) Stop codons can start translation.
   Answer: b) Some amino acids are coded by more than one codon.

5. How many stop codons are there in the genetic code?

   a) 1
   b) 2
   c) 3
   d) 4
   Answer: c) 3