Molecular Basis Of Inheritance

Expressed Sequence Tags (ESTs) are a significant component in the study of gene expression and are particularly relevant in genomic research. Let us explore the concept to identify the correct choice from the provided options.

Explanation:

1. What are ESTs?

   Expressed Sequence Tags (ESTs) are short sub-sequences of cDNA (complementary DNA) sequences. They are derived from mRNA (messenger RNA) and represent the portions of a gene that are expressed as RNA.

2. Role of ESTs:

   ESTs serve as a marker for gene expression studies. They help in identifying gene transcripts and are used to determine gene activity levels in different tissues. This provides insight into functional genomics and gene mapping.

3. Analyzing the Options:
   • Genes expressed as RNA - This correctly defines ESTs as they are derived from mRNA, which represents genes expressed as RNA.
   • Polypeptide expression - This describes protein synthesis, not directly related to ESTs, which are about nucleic acids.
   • DNA polymorphism - This refers to variations in DNA sequences among individuals and is not specifically related to ESTs.
   • Novel DNA sequences - This is a broader term that could include new sequences but doesn't specifically relate to the expression of genes as RNA.
4. Conclusion:

   Based on the explanation, the correct option is Genes expressed as RNA, as it directly correlates with the nature and purpose of ESTs.

The question asks us to identify the feature of the genetic code that allows bacteria to produce human insulin through recombinant DNA technology. The correct answer to this question is "Genetic code is nearly universal." Let's break down why this is the correct answer:

1. Understanding the Genetic Code:

   The genetic code consists of nucleotide triplets called codons, each of which specifies a particular amino acid. This code is critical for translating genetic information from nucleic acid sequences into proteins.

2. Universality of the Genetic Code:

   The term "nearly universal" means that the genetic code is the same across almost all organisms, from bacteria to humans. This universality allows genes from one organism to be expressed in another. For example, human insulin genes can be inserted into bacteria, and due to the nearly universal nature of the genetic code, bacteria can produce human insulin.

3. Applying this to Recombinant DNA Technology:

   In recombinant DNA technology, a gene from one organism (like human insulin) can be cloned into a vector that is subsequently introduced into a bacterial cell. Because of the 'nearly universal' nature of the genetic code, the bacteria can read the human insulin gene and produce the insulin protein just as human cells would.

4. Ruling Out Other Options:
   • Genetic code is not ambiguous: This feature means that each codon codes for only one amino acid and is not relevant to expressing genes across different species.
   • Genetic code is redundant: It refers to the fact that different codons can specify the same amino acid, which is unrelated to cross-species expression.
   • Genetic code is specific: This is similar to 'non-ambiguous,' meaning each codon specifies a specific amino acid, not pertinent to the cross-species genetic expression context.
5. Conclusion:

   The nearly universal nature of the genetic code is what facilitates the expression of human genes in bacteria using recombinant DNA technology. Therefore, "Genetic code is nearly universal" is the correct answer.

DNA fingerprinting is a biochemical test used for the identification of individuals based on their unique DNA characteristics. The technique involves analyzing specific regions within an individual's DNA, which exhibit variability or differences. Let's understand what these regions are by evaluating each option:

• Polymorphic DNA: Polymorphism refers to the presence of multiple forms of a particular DNA sequence in the genome. However, "Polymorphic DNA" is a broad term that doesn't specifically refer to the differentiated regions used in DNA fingerprinting.
• Satellite DNA: This refers to highly repetitive DNA sequences that are typically found in the centromeric regions of chromosomes. While these regions can be part of repetitive DNA, they are not specifically the same sections focused on for fingerprinting.
• Repetitive DNA: This is the correct answer. Repetitive DNA consists of sequences that are repeated multiple times throughout the genome. Within these repetitive sequences are regions called Variable Number Tandem Repeats (VNTRs) and Short Tandem Repeats (STRs), which are specifically targeted in DNA fingerprinting because they vary significantly among individuals.
• Single nucleotides: This refers to individual nucleotides, which are the fundamental building blocks of DNA. Single Nucleotide Polymorphisms (SNPs) are another source of genetic variation but are not the main focus in traditional DNA fingerprinting.

In conclusion, DNA fingerprinting involves identifying differences in specific repetitive DNA regions that include VNTRs and STRs. These regions are highly variable among individuals, making them ideal for distinguishing between different DNA samples. Therefore, the correct answer is Repetitive DNA.

RNA polymerase III is one of the three main types of RNA polymerases found in eukaryotic cells, each having distinct roles during the process of transcription. The key function of RNA polymerase III is to transcribe the genes that code for small RNA molecules. Among these are:

• tRNA (transfer RNA): Essential for the translation process as it carries amino acids to the ribosome, helping to decode the mRNA into a polypeptide.
• 5S rRNA (5S ribosomal RNA): A component of the large subunit of the ribosome, playing a crucial role in protein synthesis.
• snRNA (small nuclear RNA): Part of the spliceosome machinery, which is involved in splicing pre-mRNA and removing introns.

The correct option for RNA polymerase III's role in eukaryotic transcription is:

• Transcribes tRNA, 5s rRNA, and snRNA

Let's evaluate why the other options are incorrect:

• Transcribes only snRNAs: RNA polymerase III transcribes snRNA, but it also transcribes tRNA and 5S rRNA.
• Transcribes rRNAs (28S, 18S, and 5.8S): These are transcribed by RNA polymerase I, not RNA polymerase III.
• Transcribes precursor of mRNA: The precursor of mRNA, or pre-mRNA, is transcribed by RNA polymerase II.

Therefore, based on the role and specificity of RNA polymerase III, the correct answer is that it transcribes tRNA, 5S rRNA, and small nuclear RNA (snRNA).