Question

Review the Chapter Concepts list on p. 231. These all center on how genetic information is stored in DNA and transferred to RNA prior to translation into proteins. Write a short essay that summarizes the key properties of the genetic code and the process by which RNA is transcribed on a DNA.

Short answer

Question: Explain the key properties of the genetic code and describe the process of RNA transcription on a DNA template. Answer: The genetic code is a set of rules defining how DNA or RNA sequences are translated into amino acid sequences in proteins. It has three main properties: 1) Triplet code - codons or groups of three nucleotides code for specific amino acids; 2) Degeneracy - most amino acids are coded by more than one codon, allowing mutation tolerance; 3) Universality - the same codons code for the same amino acids in almost all organisms. Transcription, the process of transferring genetic information from DNA to RNA, comprises three stages: Initiation - RNA polymerase binds to a DNA promoter, unwinding the double helix; Elongation - RNA polymerase moves along the DNA template, adding complementary RNA nucleotides; Termination - transcription ends upon encountering a DNA terminator sequence, releasing the RNA molecule.

Step-by-step solution

Introduction

Genetic information is stored in DNA and transferred to RNA, which is later translated into proteins, the functional molecules in cells. In this essay, the key properties of the genetic code and the process of RNA transcription on a DNA template will be summarized.

Key Properties of the Genetic Code

The genetic code is the set of rules that determine how the nucleotide sequence in DNA or RNA is translated into the amino acid sequence in proteins. There are three main properties of the genetic code: 1. Triplet code: The genetic code is a triplet code, with each group of three nucleotides (called a codon) coding for a specific amino acid. There are 64 possible codons (4^3 combinations of the four nucleotides), of which 61 code for the 20 amino acids and 3 function as stop codons, signaling the end of translation. 2. Degeneracy: The genetic code is degenerate, meaning that most amino acids are coded for by more than one codon. This redundancy allows for some tolerance of mutations, as a single nucleotide change may not necessarily result in a different amino acid. 3. Universality: The genetic code is largely universal, with few exceptions, meaning that the same codons code for the same amino acids in almost all organisms. This shared genetic language supports the concept of a common ancestor for all life on Earth.

RNA Transcription Process

Transcription is the process by which genetic information stored in DNA is transferred to a complementary RNA molecule. This process occurs in three main stages: 1. Initiation: Transcription begins when an enzyme called RNA polymerase binds to a specific sequence on the DNA (the promoter). This binding unwinds the DNA double helix, exposing the template strand that will be used for RNA synthesis. 2. Elongation: RNA polymerase moves along the template strand, "reading" the DNA sequence and adding complementary RNA nucleotides to the growing RNA chain. Adenine (A) in DNA binds to uracil (U) in RNA, whereas cytosine (C) and guanine (G) bind as they do in DNA. 3. Termination: Transcription ends when RNA polymerase encounters a specific DNA sequence (the terminator) that signals the end of the gene. At this point, the RNA molecule is released, and the DNA double helix reforms. In summary, the genetic code is a triplet, degenerate, and universal code that translates nucleotide sequences in DNA or RNA into amino acid sequences in proteins. The transcription process transfers genetic information from DNA to RNA, which later undergoes translation to produce functional proteins.