31 Years NEET Previous Year Questions: Molecular Basis of Inheritance - 2 - NEET MCQ

23sr RNA acts as a catalyst in a bacterial cell.
Topic in NCERT: Translation
Line in NCERT:  The ribosome also acts as a catalyst (23S rRNA in bacteria is the enzyme- ribozyme) for the formation of peptide bond.

Satellite DNA is useful in forensic science. The polymorphism of minisatellite, microsatellite and minivariant repeats is analysed for DNA finger printing, DNA profiling. It helps in the resolution of crimes, legal disputes etc.

Topic in NCERT: Dna fingerprinting

Line in NCERT: The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA. Depending on base composition (A : T rich or G:C rich), length of segment, and number of repetitive units, the satellite DNA is classified into many categories, such as micro-satellites, mini-satellites etc. These sequences normally do not code for any proteins, but they form a large portion of human genome. These sequence show high degree of polymorphism and form the basis of DNA fingerprinting. Since DNA from every tissue (such as blood, hair-follicle, skin, bone, saliva, sperm etc.), from an individual show the same degree of polymorphism, they become very useful identification tool in forensic applications

Statement (ii) is accurate because the repressor binds to the operator region to block transcription when lactose is not present. Statement (iv) is true as the lac operon model was indeed elucidated by Francois Jacob and Jacque Monod, earning them the Nobel Prize in Physiology or Medicine in 1965.

Statement (i) is incorrect because it is allolactose, a form of lactose, not glucose or galactose, that binds to the repressor and inactivates it. Statement (iii) is also incorrect; the z-gene codes for β-galactosidase, not permease (which is encoded by the y-gene).

Topic in NCERT: The lac operon

Line in NCERT: "the elucidation of the lac operon was also a result of a close association between a geneticist, francois jacob and a biochemist, jacque monod."
The z gene codes for beta-galactosidase (β-gal), which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose.

Semiconservative replication of DNA was first demonstrated in Escherichia coli. E. coli is a common type of bacteria that can get into food, like beef and vegetables. The strange thing about these bacteria is that they are not always harmful to you. E. coli normally lives inside your intestines, where it helps your body breakdown and digest the food you eat.

Topic in NCERT: The experimental proof

Line in NCERT: "it is now proven that dna replicates semiconservatively. it was shown first in escherichia coli and subsequently in higher organisms, such as plants and human cells."

Splicing is the removal of introns and joining the exons in a defined order in a transcription unit. In molecular biology, splicing is a modification of RNA after transcription, in which introns are removed and exons are joined.

Topic in NCERT: Types of rna and the process of transcription

Line in NCERT: "hence, it is subjected to a process called splicing where the introns are removed and exons are joined in a defined order."

The genetic code consists of 64 triplets of nucleotides. These triplets are called codons. With three exceptions, each codon encodes for one of the 20 amino acids used in the synthesis of proteins. That produces some redundancy in the code. Most of the amino acids being encoded by more than one codon. The genetic code can be expressed as either RNA codons or DNA codons.
Topic in NCERT: The Genetic Code
Line in NCERT: The codon is read in mRNA in a contiguous fashion. There are no punctuations.

Purine is an organic nitrogenous base sparingly soluble in water, that gives rise to a group of biologically important derivatives, notably adenine and guanine, which occur in nucleotides and nucleic acids (DNA and RNA). 
Topic in NCERT: The DNA
Line in NCERT : There are two types of nitrogenous bases – Purines (Adenine and Guanine), and Pyrimidines (Cytosine, Uracil and Thymine).

GCU indicates alanine but GUU indicates valine. Stop codons are UAG, UGA and UAA AUG is the most common start codon which does for methionine. UUA indicates leucine but UCA indicates serine. 

Topic in NCERT: Stop codons

Line in NCERT: "uaa, uag, uga are stop terminator codons."

In the DNA molecule, there are two strands which run anti parallel one is 5' - 3' direction and other in 3' -5' direction, the two chains are held together by hydrogen bonds between their bases. Adenine (A), a purine of one chain his exactly opposite thymine (T), a pyramidine of the other chain. Similarly, cytosine (C), a pyrimidine lies opposite guanine (G), a purine. This allows a sort of lock & key arrangment between large sized purine & small sized pyrimidine. It is strengthened by the appearance of hydrogen bonds between the two. 

Topic in NCERT: Double-helix structure of dna

Line in NCERT: "the two chains have anti-parallel polarity. it means, if one chain has the polarity 5'3', the other has 3'>5'."

A sequential expression of a set of human genes is the DNA sequence. Because gene is the functional part of DNA sequence.

Topic in NCERT: Molecular basis of inheritance

Line in NCERT: "the dna sequence coding for trna or rrna molecule also define a gene."

The nucleosome model explains the packaging of histone proteins and DNA in the chromatin material which forms the chromosome.

Topic in NCERT: Nucleosome structure and function

Line in NCERT: "the negatively charged dna is wrapped around the positively charged histone octamer to form a structure called nucleosome."

Operons are segments of genetic material which function as regulated unit or units that can be switched on and switched off. An operon consists of one to several structural genes. (Three in lac operon) These are genes which produce mRNAs for forming polypeptides / proteins / enzymes. Z (produces enzyme β galactosidase for splitting lactose into glucose and galactose). Y (produces enzyme galactoside permease required in entry of lactose) A (produces enzyme thiogalactoside trans- acetylase).
The three structural genes of the operon produce a single polycistronic mRNA.

Topic in NCERT: Lac operon

Line in NCERT: "the z gene codes for beta-galactosidase (β-gal), which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose."

AUG—It codes for methionine only in both prokaryotes and eukaryotes, it is also an initiation codon.

Topic in NCERT: Functions of aug codon

Line in NCERT: "aug has dual functions. it codes for methionine (met), and it also act as initiator codon."