Topic 4 : Mutations NEET Style Questions - IBDP, MYP, AP, iGCSE, A-Level

Question

Now-a-days, it is possible to detect the mutated gene causing cancer by allowing radioactive probe to hybridise its complimentary DNA in a clone of cells, followed by its detection using autoradiography because [NEET 2021]

(a) mutated gene partially appears on a photographic film

(b) mutated gene completely and clearly appears on a photographic film

(d) mutated gene does not appear on photographic film as the probe has complementarity with it

Answer/Explanation

Ans. (c)
Autoradiography is an imaging technique that uses radioactive sources contained within the exposed sample. The single-stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarity with the mutated gene.

Question

Under which of the following conditions will there be no change in the reading frame of following mRNA? 5’AACAGCGGUGCUAUU3′ [NEET (National) 2019]

(a) Deletion of G from 5 th position

(b) Insertion of $A$ and $G$ at 4 th and 5th positions, respectively

(d) Insertion of $G$ at 5 th position

Answer/Explanation

Ans. (c)

The reading frame of given mRNA will not change even after the deletion of GGU from 7 th, 8th and 9 th positions. However, the amino acid glycine will not be formed at third position in this case which is being coded by GGU. In rest of the cases, insertion or deletion of one or two nucleotide bases would result in the complete alteration in the reading frame of mRNA.

Question

A cell at telophase stage is observed by a student in a plant brought from the field. He tells his teacher that this cell is not like other cells at telophase stage.
There is no formation of cell plate and thus the cell is containing more number of chromosomes as compared to other dividing cells. This would result in [NEET 2016, Phase 1]

(a) polyploidy

(b) somaclonal variation

(d) aneuploidy

Answer/Explanation

Ans. (a)

Polyploid cells have a chromosome number that is more than double the haploid number, e.g. Triticum aestivum (wheat) is a hexaploid (6n).

Question

Point mutation involves [CBSE AIPMT 2009]

(a) insertion

(b) change in single base pair

(d) deletion

Answer/Explanation

Ans. (b)

The point mutations involve alterations in the structure of gene by altering the structure of DNA, i.e. change in single base pair. Point mutations are of two types, i.e. base pair substitution and frameshift substitution. Insertion is the addition of one or more nitrogenous bases to a nucleotide chain. Duplication is the presence of one block of genes more than once in a haploid component. Deletion is the removal of one or more nitrogenous bases from a nucleotide chain.

Question

Select the incorrect statement from the following [CBSE AIPMT 2009]

(a) linkage is an exception to the principle of independent assortment in heredity

(b) galactosemia is an inborn error of metabolism

(d) baldness is a sex limited trait

Answer/Explanation

Ans. (d)

Out of the given statements (d) is incorrect because baldness is not a sex-limited trait.

Question

In a mutational event, when adenine is replaced by guanine, it is the case of [CBSE AIPMT 2004]

(a) frameshift mutation

(b) transcription

(d) transversion

Answer/Explanation

Ans. (c)

In case of transition, purine base is replaced by another purine (e.g. $A \rightleftharpoons G$ ) and pyrimidine is replaced by vice versa. In case of transversion purine is replaced by a pyrimidine and vice versa.

Question

One of the parents of a cross has mutation in its mitochondria. In that cross, that parent is taken as a male. During segregation of $\mathrm{F}_2$-progenies that mutation is found in [CBSE AIPMT 2004]

(a) one-third of the progenies

(b) none of the progenies

(d) fifty per cent of the progenies

Answer/Explanation

Ans. (b)
In the present case the male parent (not female) had mutation in mitochondria, there are negligible chances of the mutation being inherited.
It is the female reproductive cell which usually carries more cytoplasm and cytoplasmic organelles than the male cell and hence, naturally would be expected to influence non-Mendelian traits.

Question

Which of the following discoveries resulted in a Nobel Prize? [CBSE AIPMT 2003]

(a) Recombination of linked genes

(b) Genetic engineering

(d) Cytoplasmic inheritance

Answer/Explanation

Ans. (c)
HJ Muller was awarded Nobel Prize in 1946 for his discovery of the production of mutations by X-ray radiation.

Question

Change in the sequence of nucleotide in DNA is called as [CBSE AIPMT 2002]

(a) mutagen

(b) mutation

(d) translation

Answer/Explanation

Ans. (b)

Change in the sequence of nucleotide in DNA is called as mutation. The point mutations involve minor changes in the genetic material, while macro mutations involve large segments of chromosomes. ‘Frameshift mutations’ includes the addition or deletion of nucleotide (not involving 3 base pairs) so that the reading frame of the RNA is shifted to left or right during translation.

Question

Male $X X$ and female $X Y$ sometime occur due to [CBSE AIPMT 2001]

(a) deletion

(b) transfer of segments in $X$ and Y-chromosomes

(d) hormonal imbalance

Answer/Explanation

Ans. (d)

Hormonal inbalance may lead to development of male characters in female or vice versa. Deletion is the removal of one or few nitrogenous bases from a nucleotide chain. Aneuploidy is a chromosomal aberration in which certain chromosomes are present in extra copies or certain are deficient in number.

Question

During organ differentiation in Drosophila, an organ is modified to another organ (such as wings may be replaced by legs). Genes responsible for such metamorphosis are called [CBSE AIPMT 2000]

(a) double dominant genes

(b) plastid genes

(d) homeotic genes

Answer/Explanation

Ans. (d)

Homeotic genes are control genes which either by getting expressed or by remaining silent during development, influence the differentiation of organs. These have been found in insects, one nematode and some plants. A DNA sequence called homeobox, present in these genes, is involved in specification of organs.A mutation that causes a body part to develop in appropriate position in an organism, is called homeotic mutation, e.g. in Drosophila, such mutation may cause legs to develop on the head in place of antennae.

Question

Mutation generally produces [CBSE AIPMT 2000]

(a) recessive genes

(b) lethal genes

(d) dominant genes

Answer/Explanation

Ans. (a)

Mutations generally produce recessive genes. Mutation is a sudden heritable change in the characteristics of an organism. The individual which shows these heritable changes is known as mutant.

Question

Which of the following is the main category of mutation? [CBSE AIPMT 1999]

(a) Somatic mutation

(b) Genetic mutation

(d) All of these

Answer/Explanation

Ans. (b)

Mutation is a sudden heritable change in genes structure of an organism. The term genetic mutation covers somatic mutation as well as germinal mutation (occurring during reproduction).

Question

Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino? [CBSE AIPMT 1998]

(a) $100 \%$

(b) $25 \%$

(d) $75 \%$

Answer/Explanation

Ans. (b)

Since, albinism is a recessive character, a child will be albino only if it is homozygous for albinism genes. Since, parents have normal skin, it means they are heterozygous.
As a result of cross between two heterozygous parents, $25 \%$ of the children will be homozygous recessive. The nature of the second child is not affected in any way by the nature of the first child because both are independent events.

Question

Which base is responsible for hotspots for spontaneous point mutations? [CBSE AIPMT 1998]

(a) Guanine

(b)Adenine

(d) 5-methylcytosine

Answer/Explanation

Ans. (d)
5-methylcytosine residues occur at the position of each hot spot. The term ‘hot spots’ was used by Benzer for the sites which are more mutable than other sites.

Question

Loss of an X-chromosome in a particular cell, during its development, results into [CBSE AIPMT 1998]

(a) diploid individual

(b) triploid individual

(d) Both (a) and (b)

Answer/Explanation

Ans. (c)

Gynandromorphs are those individuals in which one part of the body is female while another part is male. It occurs due to the irregularity in mitosis at the first cleavage of the zygote.
One of the X-chromosomes of an XX (female) zygote lags in the spindle, one daughter nucleus receives only one X-chromosomes, while the other receives two X-chromosomes. A mosaic body pattern is thus established which is known as gynandromorph.

Question

The formation of multivalents at meiosis in diploid organism is due to [CBSE AIPMT 1998]

(a) monosomy

(b) inversion

(d) reciprocal translocation

Answer/Explanation

Ans. (d)

The formation of multivalents at meiosis in diploid organism is due to the reciprocal translocation.

Question

A mutation at one base of the first codon of a gene produces a non-functional protein. Such a mutation is referred as [CBSE AIPMT 1997]

(a) frameshift mutation

(b) mis-sense mutation

(d) reverse mutation

Answer/Explanation

Ans. (b)

If mutation at one base of the first codon of a gene takes place then all the subsequent codons will be out of register (genetic code). This results into the formation of mis-sense protein which is formed due to the mutation in the first base of first codon and thus called missense mutation.

Question

Different mutations referrable to the same locus of chromosome give rise to [CBSE AIPMT 1997]
(a)pseudoalleles

(b) polygenes

(d) multiple alleles

Answer/Explanation

Ans. (d)

The phenomenon of multiple allelism is the simultaneous occurrence of more than two alleles (multiple alleles)at a given gene locus. Any mutation occurring within a gene (at the same locus) will give rise to a new form or new allele of that gene.

Question

HJ Muller was awarded Nobel Prize for his [CBSE AIPMT 1996]

(a) discovery that chemicals can induce gene mutations

(b) discovery that ionizing radiations can induce gene mutations

(d) efforts to prevent the use of nuclear weapons

Answer/Explanation

Ans. (a)

HJ Muller was awarded Nobel Prize for discovering that ionizing radiations can induce gene mutations.

Question

The most striking example of point mutation is found in a disease called [CBSE AIPMT 1995]

(a) thalassemia

(b) night blindness

(d) sickle-cell anaemia

Answer/Explanation

Ans. (d)

Sickle-cell anaemia is an example of point mutation. It is a genetic disease reported from negroes due to a molecular mutation of gene $\mathrm{Hb}^{\wedge}$ on chromosome 11 which produces $\beta$-chain of adult haemoglobin. In this disease nucleotide triplet CTC is changed to $\mathrm{CAC}$, these changes takes place at a particular point of chromosome, so they are called as point mutation.

Question

Out of $A=T, G \equiv C$ pairing, bases of DNA may exist in alternate valency state owing to arrangement called [CBSE AIPMT 1994]

(a) analogue substitution

(b) tautomerisational mutation

(d) point mutation

Answer/Explanation

Ans. (b)
Tautomerisation occurs through rearrangement of electrons and protons of the molecules. Due to this the purines and pyrimidines in DNA and RNA may exist in several alternate forms or tautomers.

Question

A normal green male maize is crossed with albino female. The progeny is albino because [CBSE AIPMT 1989]

(a) trait for albinism is dominant

(b) the albinos have biochemical to destroy plastids derived from green male

(d) green plastids of male must have mutated

Answer/Explanation

Ans. (c)

Besides nucleus some genes are also present in the cytoplasm of the female parent, these genes are called plasmogenes. In the given example the progeny is albino because of inheritance of plastids from female parent.

Question

Haploids are able to express both recessive and dominant alleles/mutations because there are [CBSE AIPMT 1988]

(a) many alleles for each gene

(b) two alleles for each gene

(d) only one allele in a gene

Answer/Explanation

Ans. (c)

In haploids there is only one allele for each gene in the individual, that’s why haploids are better for mutation work because in them all mutations whether dominant or recessive are expressed.

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