Molecular Basis Of Inheritance

DNA dependent DNA polymerase catalyses polymerization only in one direction (5' - 3'). This means that it can only add nucleotides to the growing DNA strand in the 5' to 3' direction. As a result, the synthesis of the DNA molecule occurs discontinuously on one strand. The other strand, known as the lagging strand, is synthesized in short fragments called Okazaki fragments, which are later joined together by DNA ligase. This process is necessary to ensure accurate replication of the DNA molecule.

Splicing refers to the process of removing introns, which are non-coding regions, from a transcription unit and joining together the exons, which are the coding regions, in a specific order. This process is crucial for generating a mature mRNA molecule that can be translated into a protein. Tailing, transformation, and capping are not related to this specific process and therefore are not the correct answers.

The correct answer is the smaller ribosomal sub-unit. During translation, mRNA first binds to the smaller ribosomal sub-unit. This binding allows for the initiation of protein synthesis and the assembly of the larger ribosomal sub-unit. The smaller sub-unit contains the mRNA binding site and plays a crucial role in the initiation of translation.

The given sequence is the coding strand of DNA in a transcription unit. During transcription, the DNA coding strand is used as a template to synthesize a complementary RNA molecule. The RNA molecule is synthesized in the 5' to 3' direction, so the sequence of the RNA molecule will be the same as the coding strand, except that thymine (T) is replaced with uracil (U). Therefore, the correct answer is 5' – A U G AA U G - 3'.

The lac operon in E. coli is a regulatory system that controls the expression of genes involved in lactose metabolism. When lactose is present in the environment, it binds to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator. This allows RNA polymerase to bind to the operator and initiate transcription of the genes involved in lactose metabolism. Therefore, the lac operon gets switched on when lactose is present and it binds to the repressor.

The genetic code is a set of rules that determines how the sequence of nucleotides in DNA or RNA is translated into the sequence of amino acids in a protein. The given statement, "A codon in mRNA is read in a non-contiguous fashion," is incorrect. In reality, a codon in mRNA is read in a contiguous fashion, meaning that the nucleotides are read consecutively in a specific order. Each codon consists of three nucleotides, and each codon codes for a specific amino acid or a stop signal. Therefore, this statement does not align with the characteristics of the genetic code.

The given DNA sequence is CGATTACAG. During transcription, DNA is used as a template to synthesize an RNA molecule. In RNA, the base thymine (T) is replaced by uracil (U). The correct answer, GCUAAUGUC, is obtained by replacing T with U in the given DNA sequence.

Meselson and Stahl did not contribute to the development of the double helix model for the structure of DNA. Rosalind Franklin, Maurice Wilkins, and Erwin Chargaff were all instrumental in the discovery and understanding of DNA's structure. Franklin's X-ray crystallography work provided key insights, Wilkins' experiments further supported the double helix structure, and Chargaff's findings on base pairing rules were crucial in understanding the composition of DNA. However, Meselson and Stahl are known for their experiments on DNA replication and the semi-conservative nature of DNA, not for their contributions to the double helix model.

RNA polymerase catalyzes the process of elongation during transcription. This is the step where RNA polymerase adds nucleotides to the growing RNA strand, using the DNA template as a guide. In this step, the RNA polymerase moves along the DNA template, unwinding the DNA helix and synthesizing the complementary RNA strand. This process continues until a termination signal is reached. Therefore, the correct answer is Elongation.

In Meselson and Stahl's experiment, they used a heavy isotope of nitrogen (15N) to label the DNA in the bacteria. They then transferred the labeled bacteria to a medium containing a lighter isotope of nitrogen (14N) and allowed them to replicate. After one round of replication, the DNA would consist of one strand labeled with 15N and one strand labeled with 14N, resulting in a ratio of 1:1. After two rounds of replication, the DNA would consist of two strands, one with 15N and one with 14N, resulting in a ratio of 1:2:1. After three rounds of replication, the DNA would consist of four strands, two with 15N and two with 14N, resulting in a ratio of 0:1:3. Therefore, after four generations, the DNA would consist of eight strands, one with 15N and seven with 14N, resulting in a ratio of 0:1:7.

The explanation provided is correct. Sickle-cell anaemia is indeed expressed only in the homozygous recessive state, meaning that an individual must inherit two copies of the sickle-cell gene (one from each parent) in order to develop the condition. The presence of valine in place of glutamic acid at position 6 in the f3 polypeptide chain is a characteristic of sickle-cell haemoglobin, and it is this abnormality that leads to the formation of sickle-shaped red blood cells and the symptoms of the disease. Therefore, the statement that "If both A and R are true, R is the correct explanation of A" is accurate in this case.

The statement mentions that DNA fingerprinting is well known for its application in paternity testing. This implies that statement A is true. The reason given states that DNA fingerprinting employs the principle of polymorphism in DNA sequences, and these polymorphisms are inheritable from parents to children. While this reason is true, it does not directly explain why DNA fingerprinting is well known for its application in paternity testing. Therefore, although both A and R are true, R is not the correct explanation of A.

The given question is asking for the sequence of tRNA that pairs with the base sequence of the codon in mRNA, which is 5' AUG-3'. The tRNA molecule has an anticodon that pairs with the codon in mRNA through complementary base pairing. In this case, the anticodon would be 5' CAU-3' because it is complementary to the codon sequence 5' AUG-3'. Therefore, the correct answer is 5' - CAU - 3'.

A-DNA refers to the form of DNA that is synthesized by using RNA as a template. This type of DNA is commonly found in some viruses. It is important to note that A-DNA is different from the more common B-DNA, which is the standard double-stranded DNA structure found in most organisms. cDNA stands for complementary DNA and is synthesized from RNA using reverse transcriptase. rDNA refers to recombinant DNA, which is formed by combining DNA molecules from different sources.

RNA is indeed a constituent component of ribosomes. Ribosomes are the cellular structures responsible for protein synthesis. They consist of ribosomal RNA (rRNA) and proteins. rRNA plays a crucial role in the functioning of ribosomes by helping to catalyze the assembly of amino acids into polypeptide chains. Therefore, the statement "It is a constituent component of ribosomes" is a valid function of RNA.