31 Years NEET Previous Year Questions: Molecular Basis of Inheritance - 1 - NEET MCQ

The RNA polymerase I transcribes rRNAs (28S, 18S, and 5.8S), whereas the RNA polymerase III is responsible for transcription of tRNA, 5srRNA, and snRNAs (small nuclear RNAs).

Hence, the correct option is D.
NCERT Reference: Page no. 111 of topic “6.5.3 Types of RNA and the process of Transcription” of chapter 6.

RNA polymerase holoenzyme binds to the promoter, unwinds DNA (open complex) and forms phosphodiester links between the initiating nucleotides. DNA polymerase, DNA ligase & DNA helicase are involved in the process of replication and not transcription.

Hence, the correct option is B.
NCERT Reference: Page no. 109 and 110 of topic “6.5.3 Types of RNA and the process of Transcription” of chapter 6.

As genetic code is nearly universal means almost all organisms (from a virus, bacteria to a tree or human being) will have amino acids coded by the same kind of codons as given in checkerboard. So, this property is utilised to produce human insulin using bacteria.

Hence, the correct option is D.
NCERT Reference: Page no. 111 of topic “6.6 GENETIC CODE” of chapter 6.
NOTE: This question is based on the basic understanding of the topic genetic code.

Semiconservative replication of DNA was proved by the work of Matthew Meselson and Franklin Stahl (1958) using bacterium Escherichia coli. 

Hence, the correct option is B.
NCERT Reference: Page no. 104 of topic “6.4 REPLICATION” of chapter 6.

• The process in which the DNA is replicated and two copies are synthesized is called DNA replication.
• It involves the formation of a replication fork. The two strands of the DNA helix separate and the new strands are formed on the original strands, known as the template strands.
• The strand which is synthesized in 3'-5' direction is the leading strand and the strand which is synthesized in the opposite direction in 5'-3' is the lagging strand which contains the Okazaki fragments as its growth is discontinuous. This strand is synthesized away from the replication fork. 

Hence, the correct option is C.
NCERT Reference: Page no. 106 of topic “6.4 REPLICATION” of chapter 6.

Histones help in packaging of DNA. In eukaryotes, DNA packaging is carried out with the help of positively charged basic proteins called histones. Histones are of five types - H₁ H₂A, H₂B, H₃ and H₄. H₁ is attached over the linker DNA. Histone contains a large proportion of the positively charged (basic) amino acids, lysine and arginine in their structure. DNA is negatively charged due to the phosphate groups on its backbone. The result of these opposite charges is strong attraction and therefore, high binding affinity between histones and DNA.

Hence, the correct option is B.
NCERT Reference: Page no. 99 of topic “6.1.2 Packaging of DNA Helix” of chapter 6.

The start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and a modified Met (fMet) in prokaryotes. The most common start codon is AUG.

Hence, the correct option is A.
NCERT Reference: Page no. 112 of topic “6.6 GENETIC CODE” of chapter 6.

• Zinc-finger analysis is used for protein analysis. The zinc finger proteins are a super family of proteins involved in numerous activities of plant growth and development.
• Polymerase chain reaction is used to amplify DNA into large amounts.
• Restriction enzymes are the endonucleases that make a cut at specific positions within the DNA.
• DNA-DNA hybridisation is a technique of molecular biology which is used to measure the similarity between DNA sequences.

Hence, the correct option is B.
NCERT Reference: Page no. 122 of topic “6.10 DNA FINGERPRINTING” of chapter 6.

Large clusters of 10 to 100 ribosomes, actively translating protein synthesis are called polysomes. They were initially named as ergosomes in 1963. However, further research by Jonathan Warner and Alex Rich characterized polysome.

Taylor labelled the DNA in Vicia faba root tip cells with radioactive thymidine and then cultured them in normal media to demonstrate a semi-conservative mode of chromosome replication.

Hence, the correct option is B
NCERT Reference: Page no. 106 of topic “6.4 REPLICATION” of chapter 6.

Thomas Hunt Morgan won the Nobel Prize (1933) in physiology or medicine for the function of chromosomes in heredity. If two genes were present on the same chromosome, the probability of getting a parental combination was much higher in the next generation as compared to the non-parental combination. He termed this physical association of gene as linkage.

In codominance both alleles are independently expressed in the heterozygote.

Example: Blood group in humans.

A pleiotropic gene regulates multiple traits (characteristics) in an individual.

RNA is single-stranded, so it doesn’t follow chargaff’s rule.

Chargaff’s rule states that DNA from any cell of all organisms should have a 1:1 ratio (base Pair Rule) of pyrimidine and purine bases, that the amount of guanine (G) is equal to cytosine (C) and the amount of adenine (A) is equal to thymine (T).

Hence, the correct option is C.
NCERT Reference: Page no. 97 of topic “6.1 THE DNA” of chapter 6.

Multiple alleles refer to the presence of more than two alternate forms of a gene which should be accommodated on two loci on a homologous pair. This is facilitated by the presence of more than one allele on the same locus of a chromosome provided one allele is present at a locus at a time. All alleles of a gene are situated on the same loci of chromosomes in organisms.

Chromosomes are classified according to the position of the centromere:

• If the centromere is present somewhere in between, but not exactly in the middle, of the chromosome, it is called submetacentric chromosomes.
• Chromosomes having a centromere exactly in the middle are called metacentric.
• Acrocentric chromosomes have the centromere located very near to its end. They appear as rod-shaped or “i “ shaped chromosomes.
• The telocentric chromosomes have the centromere located at the end of the chromosome.

• In negative inducible operons, a regulatory repressor protein is normally bound to the operator, which prevents the transcription of the genes in the operon.
• If an inducer molecule is present, it binds to the repressor and changes its conformation so that it is unable to bind to the operator. This allows for expression of the operon.
• The lac operon is a negatively controlled inducible operon, where the inducer molecule is allolactose.

Hence, the correct option is A.
NCERT Reference: Page no. 117 of topic “6.8.1 The Lac operon” of chapter 6.

In translocation, the movement of a gene takes place from one linkage group to another between non-homologous chromosomes.

Chargaff's rule states:

• Molar amount of adenine(A) = Molar amount of thymine(T)
• Molar amount of guanine(G) = Molar amount of cytosine(C)

Hence, G is 17%, so, C = 17% and A = 33%, so, T = 33%
Hence, the correct option is B.
NCERT Reference: Page no. 97 of topic “6.1 THE DNA” of chapter 6.

The genotype of a man with blood group A can be IAIA or IAi. Similarly woman with blood group B, the genotype can be IBIB or IBi. Hence the offspring can have all the possible blood types, i.e. A, B, AB and O.

• Transcription is the process of copying genetic information from one strand of the DNA into RNA.

• Wherein the principle of complementarity guesses the process of transcription.

• Transcription is writing information from DNA to mRNA not DNA to t-RNA.

Transcription

Hence, the correct option is A.
NCERT Reference: Page no. 107 of topic “6.5 TRANSCRIPTION” of chapter 6.

• Frederick Griffith (1928), a British Medical officer described the phenomenon of bacterial transformation.
• He carried out an experiment with Streptococcus pneumoniae (bacterium causing pneumonia) which is used to infect mice.
• By using S Strain (heat-killed) and R strain (live) it was concluded that R strain has been transformed by some material of S strain which makes R strain virulent and enables to synthesize smooth polysaccharide.

Fig: Griffith’s experiment on mice

Hence, the correct option is C.
NCERT Reference: Page no. 100 of topic “6.2 THE SEARCH FOR GENETIC MATERIAL” of chapter 6.

• BAC is a DNA construct, based on a functional fertility plasmid (F plasmid) used for transforming and cloning in bacteria ( E.coli ). 
• Yeast artificial chromosomes (YACs) are genetically engineered chromosomes derived from the DNA of the yeast, Saccharomyces cerevisiae, which is then ligated into a bacterial plasmid.
• By inserting large fragments of DNA, from 100–1000 kb, the inserted sequences can be cloned and physically mapped using a process called chromosome walking.

Hence, the correct option is B.
NCERT Reference: Page no. 119 of topic “6.9 HUMAN GENOME PROJECT” of chapter 6.

In prokaryotes (bacteria) the 23srRNA  of the larger subunit of ribosome is the enzyme ribozyme that catalyzes peptide bond formation.

Hence, the correct option is A.
NCERT Reference: Page no. 115 of topic “6.7 TRANSLATION” of chapter 6.

Triple X syndrome occurs in women, who inherit three X chromosomes--their genotype is XXX. This type of syndrome is very rare and occurs due to defects in meiosis 1 and 2 during gamete formation in the mother and produces abnormal ova.