Problem 6 - Biology

Question

A cDNA clone contains (a) introns (b) exons (c) anticodons (d) a and b (e) b and c.

Step-by-Step Solution

Answer

(b) exons

Step 1: Understand cDNA

Complementary DNA (cDNA) is synthesized from a messenger RNA (mRNA) template. This means it reflects the sequence of the mRNA without the non-coding regions that are typically found in genomic DNA.

Step 2: Identify Components of cDNA

Since cDNA is synthesized from mRNA, it consists only of exons. Introns, which are non-coding regions found in genomic DNA, are spliced out during the processing of mRNA. Anticodons are not involved in the cDNA structure; they are a part of tRNA molecules that participate in translation.

Step 3: Conclusion

Given the understanding of what cDNA contains, we can determine that a cDNA clone includes (b) exons as it reflects the continuous coding sequence from the processed mRNA.

Key Concepts

Exons

Exons are the pieces of genetic material that provide the instructions for making proteins, the workhorses of cells. They are part of a gene that remains in the mRNA after the mRNA undergoes processing.
Unlike introns, which are non-coding sequences removed during mRNA processing, exons are spliced together to form a continuous sequence.
This sequence is then translated into a protein.

• Role in Genetic Code: Exons contain codons, each of which codes for specific amino acids.
• Importance in Proteins: The order and number of exons can determine the structure and function of the resulting protein.
• Mutation Sensitivity: Changes or mutations in exons can affect protein function, potentially leading to diseases.

Understanding exons is fundamental in studying genetic expression since they directly influence how genes carry out their roles in the cell.

mRNA

Messenger RNA (mRNA) serves as a critical intermediary between the genetic instructions in DNA and the production of proteins. It is synthesized from a DNA template during the process called transcription.
The mRNA sequence is essentially a copy of a gene that can travel out of the cell nucleus. This allows the cell machinery to read the sequence and produce proteins.

• Transcription to Translation: In the genetic process, mRNA is transcribed from DNA and then translated into a protein at ribosomes.
• Post-Transcriptional Modifications: Before mRNA can be translated into protein, it must be processed. This involves splicing, which removes introns (non-coding elements) and links exons together.
• Characteristics: mRNA contains codons, which are triplets of bases that correspond to amino acids or a stop/start signal in the translation process.

mRNA is vital for maintaining the proper production and regulation of proteins, allowing organisms to function and adapt to changes in their environment.

Genomic DNA

Genomic DNA is the complete set of DNA in a living organism, encompassing all of its genetic information. This includes both genes (coding regions) and introns (non-coding regions).
The structure of genomic DNA is complex, with the majority being non-coding sequences—including regulatory regions, introns, and sequences that have structural roles or are remnants of evolutionary processes.

• Comprehensive Code: Genomic DNA includes hundreds of thousands of genes necessary for the development, functioning, and reproduction of an organism.
• Diverse Functions: In addition to genes that code for proteins, genomic DNA contains regions that control gene expression and influence other genomic interactions.
• Variation: Differences in genomic DNA account for genetic diversity both within and between species, leading to varied traits and characteristics.

Understanding genomic DNA is crucial for genetic studies, biotechnology, and medical research, providing insights into the genetic blueprint of life.