Problem 2 - Biology Today and Tomorrow with Physiology

Question

RNAs form by ________ ; proteins form by _______ . a. replication; translation b. translation; transcription c. transcription; translation d. replication; transcription

Step-by-Step Solution

Answer

RNAs form by transcription; proteins form by translation. Option (c) is correct.

Step 1: Understand the Biological Processes

To solve this question, it's important to understand the basic processes involved in the flow of information in a cell. DNA is transcribed into RNA, and then RNA is translated into protein. These processes are part of the central dogma of molecular biology.

Step 2: Identify the Process for RNA Formation

RNA is formed by the process of transcription. In transcription, the DNA sequence is copied into a complementary RNA sequence. This step is crucial in the expression of genetic information.

Step 3: Identify the Process for Protein Formation

Proteins are formed by the process of translation. During translation, the RNA sequence is used to direct the synthesis of a protein, with the sequence of nucleotides in mRNA determining the sequence of amino acids in the protein.

Step 4: Match Processes with Answer Options

Now match the biological processes with the given options: - (c) transcription; translation Given the processes for RNA and protein formation, option (c) correctly identifies that RNA forms by transcription and proteins form by translation.

Key Concepts

RNA Transcription

RNA transcription is the first step in the transfer of genetic information from DNA to proteins. It occurs in the cell nucleus and involves the synthesis of RNA from a DNA template. During transcription, an enzyme called RNA polymerase attaches to the DNA at a region called the promoter.
This enzyme unwinds the DNA strands, allowing one of them to be used as a template.
Here’s how transcription proceeds:

• Initiation: RNA polymerase binds to a specific region of DNA to start transcription.
• Elongation: The enzyme moves along the DNA, adding nucleotides to the growing RNA strand. These nucleotides are complementary to the DNA template.
• Termination: Transcription continues until the enzyme reaches a termination signal, where the new RNA molecule, now called mRNA, is released.

This mRNA then carries the genetic code from the DNA to the ribosome, where protein synthesis occurs.

Protein Translation

Protein translation is the next critical step, where the genetic code carried by mRNA is used to create proteins. This process takes place in the cytoplasm of the cell, specifically on the ribosome.
Ribosomes are the molecular machines that read the sequence of mRNA and translate it into a sequence of amino acids to form a protein.
Key steps in protein translation include:

• Initiation: The ribosome assembles around the mRNA and the first tRNA, which is called the initiator tRNA, attaches to the start codon.
• Elongation: Transfer RNAs (tRNAs) bring amino acids to the ribosome, which are added to a growing polypeptide chain according to the sequence of codons in the mRNA. Each tRNA matches with its complementary mRNA codon.
• Termination: When a stop codon on the mRNA is reached, the process ends, and the newly formed polypeptide, now a protein, is released.

Each protein formed is crucial for various functions and structures within the cell.

Genetic Information Flow

The flow of genetic information from DNA to RNA to protein is at the heart of the central dogma of molecular biology. It describes how genes are expressed into functional products: primarily proteins.
Here's a simple breakdown of the concept:

• DNA and its role: DNA contains the blueprint of life. It holds all necessary information to build and maintain an organism.
• Transcription: This is the process of copying DNA's genetic code into mRNA, mediating an exact transfer of information.
• Translation: mRNA is decoded to form a specific sequence of amino acids, resulting in the creation of proteins.

The central dogma emphasizes that the transfer of information is unidirectional: from DNA to RNA to protein, not the other way around.
It ensures that the accurate reading and expression of genes occurs, maintaining the organism's biological integrity.