NEET Biology Molecular Basis of Inheritance MCQs Set 26

Multiple Choice Questions (MCQs) for NEET Biology: Molecular Basis of Inheritance

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Multiple Choice Questions

Question 1: Genes are packaged into a bacterial chromosome by
(a) histones
(b) basic protein
(c) acidic protein
(d) actin
Show Answer & Explanation

Answer: (b) basic protein

Explanation:
1. In bacteria the DNA is held in the nucleoid with the help of basic proteins and polyamines. Histones occur in eukaryotes.

Teacher's Note:
1. The DNA is negatively charged.
2. Basic proteins bind the DNA.

Question 2: The codons causing chain termination are
(a) TAG, TAA, TGA
(b) GAT, AAT, AGT
(c) AGT, TAG, UGA
(d) UAA, UAG, UGA
Show Answer & Explanation

Answer: (d) UAA, UAG, UGA

Explanation:
1. The termination codons in mRNA are UAA, UAG and UGA. The DNA has T, but mRNA has U.

Teacher's Note:
1. The options with T are DNA codes.
2. Use U for the RNA codons.

Question 3: The RNA that picks up specific amino acid from amino acid pool in the cytoplasm to ribosome during protein synthesis is called
(a) mRNA
(b) tRNA
(c) rRNA
(d) RNA
Show Answer & Explanation

Answer: (b) tRNA

Explanation:
1. tRNA picks up specific amino acids from the cytoplasm and takes them to the ribosome.

Teacher's Note:
1. It is an adaptor molecule.
2. tRNA carries amino acids.

Question 4: Protein synthesis in an animal cell takes place
(a) only in the cytoplasm
(b) in the nucleolus as well as in the cytoplasm
(c) in the cytoplasm as well as in mitochondria
(d) only on ribosomes attached to a nucleus
Show Answer & Explanation

Answer: (c) in the cytoplasm as well as in mitochondria

Explanation:
1. In an animal cell proteins are made on ribosomes in the cytoplasm and also in the mitochondria, which have their own ribosomes.

Teacher's Note:
1. The nucleolus only assembles ribosomes.
2. Mitochondria make some proteins.

Question 5: The mutations are mainly responsible for
(a) constancy in organisms
(b) variation in organisms
(c) increasing the population rate
(d) maintaining genetic continuity
Show Answer & Explanation

Answer: (b) variation in organisms

Explanation:
1. Mutations are the source of variation in organisms.

Teacher's Note:
1. They provide raw material for evolution.
2. Mutation produces variation.

Question 6: The formation of multivalents at meiosis in diploid organism is due to
(a) monosomy
(b) inversion
(c) deletion
(d) reciprocal translocation
Show Answer & Explanation

Answer: (d) reciprocal translocation

Explanation:
1. The formation of multivalents in meiosis in a diploid organism is due to reciprocal translocation between non-homologous chromosomes.

Teacher's Note:
1. Chromosomes then pair as a cross-shaped quadrivalent.
2. Translocation gives multivalents.

Question 7: Which base is responsible for hot spots for spontaneous point mutations ?
(a) Guanine
(b) Adenine
(c) 5-bromouracil
(d) 5-methylcytosine
Show Answer & Explanation

Answer: (d) 5-methylcytosine

Explanation:
1. 5-methylcytosine is easily deaminated to thymine, so it is a hot spot of spontaneous point mutations.

Teacher's Note:
1. Deamination changes C to T.
2. Methylated cytosine mutates readily.

Question 8: DNA elements, which can switch their position, are called
(a) exons
(b) introns
(c) cistrons
(d) transposons
Show Answer & Explanation

Answer: (d) transposons

Explanation:
1. DNA elements that can change their position in the genome are called transposons (jumping genes).

Teacher's Note:
1. Barbara McClintock discovered them in maize.
2. Transposons are mobile.

Question 9: In DNA when AGCT occurs, their association is as per which of the following pair?
(a) AC-GT
(b) AG-CT
(c) AT-GC
(d) All of these
Show Answer & Explanation

Answer: (c) AT-GC

Explanation:
1. In DNA, adenine pairs with thymine (A-T) and guanine pairs with cytosine (G-C).

Teacher's Note:
1. A and T have two hydrogen bonds, G and C have three.
2. Chargaff's rule.

Question 10: The Pneumococcus experiment proves that
(a) DNA is the genetic material
(b) RNA sometime controls the production of DNA and proteins
(c) bacteria undergo binary fission
(d) bacteria do not reproduce sexually
Show Answer & Explanation

Answer: (a) DNA is the genetic material

Explanation:
1. Griffith's Pneumococcus experiment showed transformation, which later proved that DNA is the genetic material.

Teacher's Note:
1. Avery and others identified DNA.
2. It shows the role of DNA.

Question 11: Mutation generally produces
(a) recessive genes
(b) lethal genes
(c) polygenes
(d) dominant genes
Show Answer & Explanation

Answer: (a) recessive genes

Explanation:
1. Most mutations produce recessive alleles.

Teacher's Note:
1. Dominant mutations are less common.
2. Recessive mutations are masked.

Question 12: During replication of DNA, its two strands separate. Each of these serves as a template for the formation of new strands. Such type of replication is called
(a) non-conservative
(b) semi-conservative
(c) flexible
(d) conservative
Show Answer & Explanation

Answer: (b) semi-conservative

Explanation:
1. The strands separate and each acts as a template for a new strand, so each daughter DNA has one old and one new strand. This is semi-conservative replication.

Teacher's Note:
1. Conservative means the old DNA stays intact.
2. Semi means half.

Question 13: ‘Signal hypothesis’ for the biosynthesis of secretory type of proteins was proposed by
(a) Camillo Golgi
(b) Blobel and Sabatini
(c) Baltimore
(d) Sheeler and Bianchi
Show Answer & Explanation

Answer: (b) Blobel and Sabatini

Explanation:
1. The signal hypothesis for secretory proteins was proposed by Blobel and Sabatini.

Teacher's Note:
1. A signal peptide guides the protein to the ER.
2. Remember the two names.

Question 14: Due to discovery of which of the following in 1980’s the evolution was termed as RNA world?
(a) mRNA, tRNA, rRNA synthesize proteins
(b) In some viruses, RNA is genetic material
(c) Some RNAs have enzymatic property
(d) RNA is not found in all cells
Show Answer & Explanation

Answer: (c) Some RNAs have enzymatic property

Explanation:
1. The discovery in the 1980s that some RNAs have enzymatic properties (ribozymes) led to the term RNA world.

Teacher's Note:
1. It suggests that RNA came before DNA.
2. Ribozymes support the RNA world.

Question 15: Gene and cistron words are sometimes used synonymously because
(a) one cistron contains many genes
(b) one gene contains many cistrons
(c) one gene contains one cistron
(d) one gene contains no cistron
Show Answer & Explanation

Answer: (c) one gene contains one cistron

Explanation:
1. A gene (cistron) is the segment of DNA coding for a polypeptide, so one gene contains one cistron.

Teacher's Note:
1. The terms are used almost synonymously.
2. One cistron for one polypeptide.

Question 16: In which direction mRNA is synthesized on DNA template?
(a) 5'3'
(b) 3'5'
(c) Both
(d) Any of these
Show Answer & Explanation

Answer: (a) 5'3'

Explanation:
1. mRNA is synthesised in the 5' to 3' direction, using the template strand read in the 3' to 5' direction.

Teacher's Note:
1. All nucleic acids grow 5' to 3'.
2. Synthesis is always 5' to 3'.

Question 17: Change in the sequence of nucleotide in DNA is called as
(a) mutagen
(b) mutation
(c) recombination
(d) translation
Show Answer & Explanation

Answer: (b) mutation

Explanation:
1. A change in the nucleotide sequence of DNA is called a mutation.

Teacher's Note:
1. A mutagen is the agent causing it.
2. Mutation means change in sequence.

Question 18: Sequence of which of the following is used to know the phylogeny ?
(a) mRNA
(b) rRNA
(c) tRNA
(d) DNA
Show Answer & Explanation

Answer: (b) rRNA

Explanation:
1. The sequence of rRNA, which is highly conserved, is used to study phylogeny.

Teacher's Note:
1. It changes slowly in evolution.
2. rRNA is used in phylogeny.

Question 19: In a DNA percentage of thymine is 20. What is the percentage of guanine ?
(a) 20%
(b) 40%
(c) 30%
(d) 60%
Show Answer & Explanation

Answer: (c) 30%

Explanation:
1. If T = 20%, A = 20%, and A + T = 40%. So G + C = 60%, and G = 30%.

Teacher's Note:
1. Chargaff's rule: A = T and G = C.
2. Subtract and halve.

Question 20: Exon part of mRNAs have code for
(a) protein
(b) lipid
(c) carbohydrate
(d) phospholipid
Show Answer & Explanation

Answer: (a) protein

Explanation:
1. The exons of mRNA code for protein (amino acid sequence).

Teacher's Note:
1. Introns are removed.
2. Exons are coding sequences.

Question 21: Genetic map is one that
(a) shows the stages during the cell division
(b) shows the distribution of various species in a region
(c) establishes sites of the genes on a chromosome
(d) establishes the various stages in gene evolution
Show Answer & Explanation

Answer: (c) establishes sites of the genes on a chromosome

Explanation:
1. A genetic map shows the positions of genes on a chromosome, based on recombination frequencies.

Teacher's Note:
1. It is also called a linkage map.
2. It shows gene locations.

Question 22: Degeneration of a genetic code is attributed to the
(a) entire codon
(b) third member of a codon
(c) first member of a codon
(d) second member of a codon
Show Answer & Explanation

Answer: (b) third member of a codon

Explanation:
1. Degeneracy of the genetic code is due to the third base of the codon (wobble position), which can vary without changing the amino acid.

Teacher's Note:
1. Codons differing in the third base often code for the same amino acid.
2. The wobble base is the third base.

Question 23: What would happen if in a gene encoding a polypeptide of 50 amino acids, 25th codon (UAU) is mutated to UAA ?
(a) A polypeptide of 49 amino acids will be formed
(b) A polypeptide of 25 amino acids will be formed
(c) A polypeptide of 24 amino acids will be formed
(d) Two polypeptides of 24 and 25 amino acids will be formed
Show Answer & Explanation

Answer: (c) A polypeptide of 24 amino acids will be formed

Explanation:
1. Changing the 25th codon UAU to UAA creates a stop codon. So translation stops, and a polypeptide of 24 amino acids is formed.

Teacher's Note:
1. It is a nonsense mutation.
2. Count the codons before the stop.

Question 24: Chromosomes in a bacterial cell can be 1-3 in number and
(a) can be either circular or linear, but never both within the same cell
(b) can be circular as well as linear within the same cell
(c) are always circular
(d) are always linear
Show Answer & Explanation

Answer: (c) are always circular

Explanation:
1. A bacterial cell has a single, double-stranded, circular chromosome in the nucleoid (rarely 1 to 3 and always circular).

Teacher's Note:
1. Plasmids are also circular.
2. Bacterial chromosomes are circular.

Question 25: During transcription, the DNA site at which RNA polymerase binds is called
(a) receptor
(b) enhancer
(c) promoter
(d) regulator
Show Answer & Explanation

Answer: (c) promoter

Explanation:
1. RNA polymerase binds to the promoter, a DNA site at the start of the transcription unit.

Teacher's Note:
1. The terminator is at the end.
2. Promoter means binding site.

Question 26: What does “lac” refer to in what we call the lac operon ?
(a) Lac insect
(b) The number, 1,00,000
(c) Lactose
(d) Lactase
Show Answer & Explanation

Answer: (c) Lactose

Explanation:
1. The word lac in the lac operon stands for lactose.

Teacher's Note:
1. The operon has lacZ, lacY and lacA genes.
2. Lac means lactose.

Question 27: During transcription holoenzyme RNA polymerase binds to a DNA sequence and the DNA assumes a saddle like structure at that point. What is that sequence called ?
(a) CAATbox,
(b) GGTTbox
(c) AAAT box
(d) TATA box
Show Answer & Explanation

Answer: (d) TATA box

Explanation:
1. The TATA box is the promoter sequence where RNA polymerase binds in transcription.

Teacher's Note:
1. The DNA bends into a saddle-like shape.
2. TATA box is the binding site.

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