Question

How is cDNA best characterized? a. CDNA results from a DNA transcript with noncoding regions removed. b. cDNA results from the reverse transcription of processed mRNA. c. cDNA is the abbreviation for deoxycytosine. d. cDNA is the circular DNA molecule that forms the bacterial genome.

Short answer

Option B: cDNA results from the reverse transcription of processed mRNA.

Step-by-step solution

- Understand the Terminology

Complementary DNA (cDNA) is a form of DNA synthesized from a single-stranded RNA template. It is often used in gene cloning or as a gene probe in molecular biology.

- Analyze Option A

Option A states that cDNA results from a DNA transcript with noncoding regions removed. However, noncoding regions (introns) are removed during mRNA processing, not during cDNA synthesis.

- Analyze Option B

Option B states that cDNA results from the reverse transcription of processed mRNA. This is correct because cDNA is made using reverse transcriptase, which synthesizes DNA from a processed mRNA template (which has no introns).

- Analyze Option C

Option C states that cDNA is the abbreviation for deoxycytosine. This is incorrect as cDNA stands for complementary DNA, not deoxycytosine.

- Analyze Option D

Option D states that cDNA is the circular DNA molecule that forms the bacterial genome. This is incorrect because bacteria have circular DNA, but it is not referred to as cDNA.

- Conclude the Correct Answer

Based on the analysis of each option, the correct characterization of cDNA is provided in Option B.

Key concepts

complementary DNA

Complementary DNA (cDNA) is a type of DNA that is synthesized from an mRNA template through a process known as reverse transcription. This process involves creating a complementary DNA sequence from an RNA sequence. Scientists often use cDNA in molecular biology to study gene expression.

cDNA is particularly useful because it represents only the expressed genes in a cell, without the introns (non-coding regions) that are present in genomic DNA. This makes cDNA a powerful tool for understanding gene function and for cloning specific genes.

In sum:

• cDNA is synthesized from mRNA
• It lacks non-coding regions
• Useful in studying gene expression and cloning

reverse transcription

Reverse transcription is the process of synthesizing DNA from an RNA template. This process is catalyzed by the enzyme reverse transcriptase.

Key steps include:

• Using an RNA template
• Reverse transcriptase to synthesize the complementary DNA
• The resulting DNA is called complementary DNA (cDNA)

Reverse transcription is a vital process in molecular biology, especially for generating cDNA libraries. It allows researchers to study gene expression by analyzing the mRNA present in a cell, which is then converted into a more stable DNA form for further study.

mRNA processing

Messenger RNA (mRNA) processing is the series of steps through which a primary RNA transcript is transformed into a mature mRNA that is ready for translation.

Key stages in mRNA processing include:

• Capping: The addition of a protective cap to the 5’ end of the primary RNA transcript
• Splicing: The removal of non-coding regions (introns) and joining together of coding regions (exons)
• Polyadenylation: The addition of a tail at the 3’ end

These modifications ensure the stability of the mRNA and play a crucial role in regulating gene expression. The processed mRNA can then be used as a template for reverse transcription to generate cDNA.

molecular biology

Molecular biology is a branch of biology that focuses on the molecular basis of biological activity. This includes studying DNA, RNA, and protein synthesis and how these macromolecules regulate cellular processes.

Key areas of study in molecular biology include:

• Gene expression
• Replication and repair of DNA
• RNA transcription and translation
• Molecular techniques such as PCR and gel electrophoresis

Understanding molecular biology is fundamental for fields such as genetics, bioinformatics, and biotechnology. Tools like cDNA synthesis and reverse transcription are crucial for many molecular biology applications, enabling researchers to explore the genetic blueprints of life.