Test: Molecular Basis of Inheritance- 2 - NEET MCQ

DNA molecules are replicated in both meiosis and mitosis.  DNA unwinds and unzips along its base pair chemical bonds.  Free nucleotides then connect to the exposed base pairs on both strands resulting in the formation of the missing side of each new DNA.

• A lac operon consists of one regulatory gene (i) and three structural genes (z, y and a).
• The “i” in regulatory gene is derived from the word “inhibitor”.

A single strand of nucleic acid tagged with a radioactive molecule is calledProbe. Probe is used to know the mechanism of transcription of DNA. Radioactive substance can be easily detected.

The structural gene (z) of the lac operon codes for β-galactosidase. It is responsible for the hydrolysis of polysaccharides. The ‘y’ genes code for permease. It increases the permeability of a cell to β-galactosidase. The ‘a’ genes code for transacetylase.

In figure above, A represent helicase and B represents single strand binding protein. These structures are formed during semiconservative replication of DNA.

The DNA segment which serves as ON-OFF switch for transcription is called an operator. Operator attach with template strand to initiate transcription process.

Codon AAA code for amino acid lysine but UUA, AUG and CCC do not code for Valine, cysteine and alanine respectively. So, AAA and lysine pair is correct option out of given options.

• The regulation of a lac operon by the repressor is known as negative regulation.
• At rare occasions, lac operons are also observed to be under the control of positive regulation.
• In negative regulation, the operon cannot transcribe the RNA polymerase enzyme.

UGA, UAG and UAAare called termination or stop codon because they do not code for any amino acid. As soon as any one of them codon is located on m-RNA translation process is stopped.

The mRNA produced by transcription of DNA consists of exons and introns. The removal of introns and joining of exons to obtain mature mRNA is called splicing. It is followed by capping and tailing.

In lac operon the word lac refers to lactose. A polycistronic structural gene is regulated by a common promoter and regulatory genes.

In lac operon concept the sequence of arrangement of structural gene is as lac Z, lac Y and lac A. The z gene codes for beta-galactosidase. The y gene code for permease and a gene encodes a transacytylase.

Figure shown above represent translation process in which protein is produced. Ribosome provide site for protein synthesis and t-RNA brings the amino acids. The ‘x’ is the polypeptide chain produced.

Autoradiogram of VNTR probe gives many band of different size. It differs from individual to individual except monozygotic twins or identical twins.

In human genome project, commonly used host were bacteria and yeast and their vectors are called as Bacterial artificial chromosome (BAC) and yeast artificial chromosome (YAC)

Genetic map up of an organism or individual lies in the DNA sequence. If two individual differs, then their DNA sequence should also be different.

• George Gamow who was a physicist mentioned that to be able to code for 20 amino acids, we require 4 bases.
• The code should also be made up of 3 nucleotides.
• The code should be made up of bases in a particular combination.

Genetic and physical map of genome was generated using information on polymorphism of restriction endonuclease recognition sites and repetitive DNA sequence called microsatellites.

The double helix describes the appearance of double-stranded DNA, which is composed of two linear strands that run opposite to each other, or anti-parallel, and twist together. Each DNA strand within the double helix is a long, linear molecule made of smaller units called nucleotides that form a chain.

UAA of mRNA do not code for any amino acids so it is a termination codon. If termination codon is present on mRNA, the protein synthesis stops abruptly at that point.

The sensitivity of fingerprinting technique has been increased by use of Polymerase chain reaction (PCR). After that single cell obtained from organism in enough for this technique.

DNA finger printing is highly reliable method of identification of individual involved in crimes. DNA a fingerprinting is a sure method in solving paternity and maternity disputes.DNA fingerprinting cannot be used to cure HIV infection.

The hybridization of probes having radioactive isotopes with various sequence of nitrogen bases with ssVNTR is called Southern blotting.

In prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression.

VNTR of two persons may be similar at certain sites but could be different at other sites because a child inherits 50% of chromosomes from mother and remaining 50% from father. VNTR genes also undergoes different kinds of mutations.