Category: Life Sciences Objective Questions

Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “Sex Determination”.

1. Genes of sex linked characters are located on the ___________
A. Chromosome 18
B. Chromosome 13
C. Chromosome 14
D. Sex chromosome
Answer: D
Clarification: The characters are said to be sex linked if their genes are located on the sex chromosome. According to modern genetics, the x-chromosome linked character is called sex-linked character while y-linked characters are called male limited characters.

2. In sex linkage, reciprocal cross yield identical results.
A. True
B. False
Answer: B
Clarification: In the case of sex linkage reciprocal cross do not yield identical results, but it shows a criss-cross inheritance pattern, i.e. male transmits its sex linked genes to all daughters who in turn transmit them to half of their male progeny.

3. Which of the following is X-linked recessive disorder?
A. Color blindness
B. Sickle cell anemia
C. PTC tasting
D. Albinism
Answer: A
Clarification: In humans, three proteins in the cons cells act as color sensors, the two color sensors are encoded by X-linked genes while one is encoded by a gene located on the seventh autosome.

4. Which of the following statement is NOT true regarding Partial sex linkage?
A. The X-Y chromosome pair during meiosis
B. Pairing occurs in the terminal region
C. The inheritance pattern in the PAR region show sex-linkage
D. PAR stands for the pseudo autosomal region
Answer: C
Clarification: The inheritance pattern of the genes present in such terminal regions (PAR) of the sex chromosome is not like that of sex-linked genes but it resembles that of autosomal genes.

5. Identify the disease which causes excessive production of uric acid.
A. Duncan muscular dystrophy
B. Lesch-Nyhan syndrome
C. Hunter syndrome
D. Hemophilia
Answer: B
Clarification: Lesch-Nyhan syndrome is an X-linked disorder which is the example of congenital hyperuriemic (excessive production of uric acid). It causes HGPRT (Hypoxanthine Guanine Phosphoribosyl Transferase) gene defective.

6. Which of the following characteristics does not belong to the Hunter syndrome?
A. Muscular deterioration
B. Abnormal hairiness
C. Mental retardation
D. Long protruding tongue
Answer: A
Clarification: Hunter syndrome is an X-linked recessive disorder where the affected person have long protruding tongue and mental retardation while muscular deterioration occurs in another disorder called Duncan muscular dystrophy.

7. Which of the following is NOT a sex-limited role?
A. Pitch of voice
B. Musculature
C. Baldness
D. Milk production
Answer: C
Clarification: Baldness is a sex-influenced character, not a sex-limited character. Sex-limited characters are those whose development is limited to only one of the two sexes.

8. Which of the following disease is characterized by excessive trinucleotide repeats (CAG)?
A. Cystic fibrosis
B. PTC tasting
C. Dwarfism
D. Huntington’s disease
Answer: D
Clarification: Huntington’s disease is an autosomal disorder which is caused by excessive trinucleotide repeats, approx 50 to 100 times more than normal condition.

9. What is pedigree analysis?
A. Record of inheritance pattern
B. Linkage map
C. Quantitative genetic
D. Polygene analysis
Answer: A
Clarification: Pedigree is a record of inheritance of certain genetic traits for two or more than two generations presenting in the form of a diagram.

10. Name the principle on which pedigree analysis work?
A. Regression
B. Probability
C. Random mating
D. ANOVA
Answer: B
Clarification: Pedigree analysis is used to study the transmission genetics where controlled process is not possible and it works on the principle of probability.

.

Life Sciences Multiple Choice Questions on “Structure of dsDNA”.

1. Who described the structure of DNA double helix?
A. Peter Mitchell
B. Andre Jagendorf
C. Ernest Uribe
D. Watson and Crick
Answer: D
Clarification: DNA double helix was first described in 1953 by Watson and Crick using X-ray diffraction. DNA fibers were obtained by Franklin and Wilkins. Watson, Crick, and Wilkins were awarded a noble prize in 1962.

2. Which form of DNA is described by Watson-Crick model?
A. B-DNA
B. Z-DNA
C. A-DNA
D. Quadraplex DNA
Answer: A
Clarification: There are many forms of DNA which are biologically important, out of which Watson-Crick double helix model describes the B form of DNA. The confirmation of DNA would depend on the hydration level, base modification etc.

3. How many base pairs are there in every helical turn of Watson-Crick double helix model?
A. 32.3
B. 11.6
C. 20
D. 10.4
Answer: D
Clarification: Watson-Crick double helix model consists of 10.4 base pairs per helical turn. Since one helical turn formed by 360° and there would be 34.3° twist angle per residue among adjacent base pair.

4. Which one of the following statement is INCORRECT for Z-DNA?
A. Left-handed DNA
B. Mostly found in alternating purine-pyrimidine sequences
C. Only one deep, narrow groove
D. Anti glycosidic bond conformation
Answer: D
Clarification: Anti glycosidic bond conformation is incorrect as in Z-DNA the sugar and glycosidic bond conformations alternate, anti for C and syn for G while in B form there is only anti glycosidic bond conformation.

5. The third strand of triple helix is paired in which scheme?
A. Hoogsteen base pair scheme
B. Intermolecular base pair scheme
C. Intramolecular base pair scheme
D. G-quartet scheme
Answer: A
Clarification: Triple helix formed by three strands polypurine, polypyrimidine and the third strand which lay in the major groove of DNA and makes a hydrogen bond to duplex. The third strand is paired in hoogsteen base pairing scheme where the central strand is purine rich.

6. Name the nitrogenous base which is found in abundance in G-quadruplex?
A. Adenine
B. Guanine
C. Cytosine
D. Thymine
Answer: B
Clarification: When nucleic acid sequences are rich in guanine and can form four-stranded structure, it will term as G-quadruplex. It is a square arrangement of guanine, stabilized by hoogsteen hydrogen bonding.

7. The stability and formation of G-quadruplex depends on __________
A. Monovalent cation
B. Divalent cation
C. Bivalent cation
D. Pentavalent ion
Answer: A
Clarification: A monovalent cation is responsible for the stability of G-quadruplex as it is present in the center of the tetrad. It can be formed in either DNA or RNA.

8. Which of this factor is not responsible for thermal denaturation of DNA?
A. PH
B. Temperature
C. Ionic strength
D. Humidity
Answer: D
Clarification: When DNA duplex is laid open to the specific conditions like temperature, pH, or ionic strength it will interrupt the hydrogen bond between strands and they are no longer held together. After denaturation, the strand separates as individual coils and the double helix is denatured.

9. Double-stranded DNA with high GC content has higher thermal stability than that of lower GC content?
A. True
B. False
Answer: A
Clarification: There is three hydrogen bond in G:C while only two between A: T, this shows higher no of hydrogen bonds and interaction in G:C than A:T. Higher G:C content has a higher melting temperature. So, it has more thermal stability as compared to A:T.

10. What is the term given to the supercoiling of circular DNA?
A. Twist number
B. Linking number
C. Writhe number
D. Cross-linking
Answer: B
Clarification: Linking number defines the no. of times one strand crosses other in closed circular DNA. It is the sum of twist number (total number of helical turn) and writhe number (supercoiling in the helix).
Lk = Tw + Wr.

11. Which of them is used to introduce negative supercoiling in DNA?
A. Type 1 topoisomerase
B. Ethidium bromide
C. Gyrase/ type 2 topoisomerase
D. SYBR gold
Answer: C
Clarification: Type 1 topoisomerase break only one strand of DNA while gyrase works on both the strands, it breaks and reseal both DNA strands and introduce negative supercoils. Ethidium bromide and SYBR gold are used to stain DNA molecules.

.

Life Sciences Multiple Choice Questions on “Nucleotide Metabolism”.

1. Salvage pathway is used in the synthesis of ___________
A. Amino acid
B. Carbohydrate
C. Nucleotide
D. Fatty acid
Answer: C
Clarification: Nucleotide synthesis takes place by two pathways: salvage pathways and de novo pathways. In de novo pathway pyrimidine base is assembled first and then attached to ribose while in the salvage pathway preformed base is recovered and reconnected to a ribose sugar.

2. All deoxyribonucleotide is synthesized by the ribonucleotides.
A. True
B. False
Answer: A
Clarification: Deoxyribonucleotide cannot be synthesized directly from de novo and salvage pathway but it is generated by the reduction of ribose from the corresponding ribonucleotide.

3. Name the precursor of RNA?
A. Glutamine
B. Cytidine
C. Orotidylate
D. Uridylate
Answer: D
Clarification: Uridylate or UMP is a major pyrimidine nucleotide formed by the decarboxylation of orotidylate (OMP) during pyrimidine synthesis. UMP further gets converted to a ribonucleotide, and act as a precursor of RNA.

4. The activity of which of the following enzyme is inhibited by the chemotherapeutic agent during deoxyribonucleotide synthesis?
A. Dihydrofolate reductase
B. Ribonucleotide reductase
C. Thymidylate synthase
D. CTP synthetase
Answer: A
Clarification: Methotrexate and aminopterin are two anticancer drugs which inhibits the activity of dihydrofolate reductase. This will stop the formation of deoxyribonucleotide or DNA and the growth of the cell stops.

5. Which of the following is not the precursor of a purine ring?
A. Glutamine
B. Lysine
C. Glycine
D. Aspartate
Answer: B
Clarification: Purine ring is derived from various precursors like glutamine (N2 and N9), glycine (C4, C5, and N7), aspartate (N1), Co₂ (C6), folate (C2 and C8). Except for lysine, all are the precursor of purine ring.

6. During purine synthesis the activity of amidotransferase enzyme is inhibited by the antitumor agent, mark the correct one.
A. Aminopterin
B. Methotrexate
C. Texol
D. Azaserine
Answer: D
Clarification: Azaserine is the structural analog of glutamine and works as an antitumor agent by preventing the activity of enzyme amidotransferase which in turn block purine synthesis.

7. What is the final product of purine degradation in mammals?
A. Guanine
B. Inosine
C. Uric acid
D. Hypoxanthine
Answer: C
Clarification: Punine nucleotides are sequentially degraded from inosine to hypoxanthine and guanine and finally to the uric acid which is excreted with the urine in the human being while in some other animals it is further degraded to urea and ammonia.

8. Name the deficiency in which T and B lymphocyte do not develop properly?
A. XLA
B. CVID
C. SCID
D. Multiple myeloma
Answer: C
Clarification: Severe combined immunodeficiency syndrome (SCID. is caused by the deficiency of adenosine deaminase which leads to increase in the cellular concentration of dATP. High level of dATP reduces dNTPs in T-lymphocytes.

9. Which of the following disorder is caused due to the high serum level of urate?
A. Gout
B. Galectosemia
C. Cystic fibrosis
D. Maple syrup urine disease
Answer: A
Clarification: Gout is caused due to the high amount of uric acid, which is the product of purine degradation. It involves precipitation of sodium urate crystals in the joints and causes inflammation.

10. Name the genetic disorder which is caused by the deficiency of enzyme HGPRT?
A. SCID
B. Lesch-Nyhan syndrome
C. Cystic fibrosis
D. Down syndrome
Answer: B
Clarification: This genetic disorder is caused by the deficiency of enzyme hypoxanthine-guanine phosphoribosyl-transferase (HGPRT). This results in increase rate of purine biosynthesis by de novo pathway and overproduction of urate.

.

Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “Bacterial Nutrition”.

1. Name the type of bacteria which uses Co₂ as a sole source of carbon for growth.
A. Organotrophs
B. Heterotrophs
C. Autotrophs
D. Lithotrophs
Answer: C
Clarification: Bacterial nutrition divides bacteria into different classes, on the basis of carbon sources these are divided into two classes i.e. autotrophs and heterotrophs. Autotrophs use carbon dioxide as a sole source of carbon while heterotrophs utilize organic carbon.

2. Name those bacteria which obtain energy from chemical compounds?
A. Chemotrophs
B. Phototrophs
C. Organotrophs
D. Heterotrophs
Answer: A
Clarification: Living organisms need a source of energy for survival, bacteria has been divided into two categories on the basis of the source of energy i.e. phototrophs which need light as their energy source and chemotrophs obtain energy from the oxidation of chemical compounds.

3. Name the type of bacteria which uses reduced inorganic substances as an electron source?
A. Autotrophs
B. Chemotrophs
C. Organotrophs
D. Lithotrophs
Answer: D
Clarification: Bacteria which uses reduced inorganic substances as their electron sources are called lithotrophs while organotrophs are the bacterial class which utilizes organic compounds as their electron source.

4. Which of the following bacteria does not belong to photolithoautotrophy nutritional class?
A. Thiomargarita namibiensis
B. Purple sulfur bacteria
C. Blue-green bacteria
D. Green sulfur bacteria
Answer: A
Clarification: Photolithoautotrophy is the class of the bacteria which utilize CO₂ as a carbon source, light energy as the energy source, and inorganic hydrogen as the electron source.

5. Purple and green non-sulfur bacteria belongs to which of the following classes?
A. Photolithoautotrophy
B. Photoorganohetrotrophy
C. Chemolithoautotrophy
D. Chemoorganohetrotrophy
Answer: B
Clarification: Purple and green non-sulfur bacteria use light energy as an energy source, organic carbon source, and organic hydrogen as the source of an electron.

6. Nitrifying bacteria belongs to the nutritional class of_______
A. Chemoorganoautotrophy
B. Photolithoautrophy
C. Chemolithoautotrophy
D. Photoorganohetrotrophy
Answer: C
Clarification: Nitrifying bacteria include species of Nitrosomonas, Nitrococcus, Nitrobactor, and Nitrococcus. These are chemolithoautotrophic organisms which get energy by oxidation of inorganic nitrogen compounds.

7. Which of the following species falls under the category of hydrogen-producing bacteria?
A. Thiobacillus thiooxidans
B. Nitrosomonas europaea
C. Nitrobacter winogradskyi
D. Alkaligenes eutrophus
Answer: D
Clarification: Alkaligenes eutrophus are gram-negative, aerobic, and rod-shaped bacteria and is classified as hydrogen-producing bacteria.

8. The exact composition of complex media should be known.
A. True
B. False
Answer: B
Clarification: A complex media is undefined in which the exact chemical composition of the medium is not known while the synthetic medium is the culture medium whose exact chemical composition should be known.

9. Which of these is NOT a selective media?
A. Blood agar
B. Eosin methylene blue agar
C. MacConkey agar
D. Mannitol salt agar
Answer: A
Clarification: Selective media are those which prevent the growth of other types of bacteria and promote the growth of only desired species.

10. Name the protein which plays an important role in cell division?
A. Actin
B. FtsZ
C. HSP
D. HU
Answer: B
Clarification: FtsZ is homologous to tubulin, which is a building block of the microtubule in eukaryotes. The concentration of FtsZ in the cell will define the frequency of cell division.

.

Life Sciences Problems focuses on “Quantitative Inheritance”.

1. Traits which show continuous variation is referred as ___________
A. Genetic disorders
B. Phenotypic variation
C. Quantitative traits
D. Qualitative traits
Answer: C
Clarification: On quantitative inheritance, the phenotype of an individual depends upon the number of dominant alleles involved. Here, all the genes show additive effects on the gene.

2. QTL is the chromosomal site at which a group of genes affecting quantitative traits located.
A. True
B. False
Answer: A
Clarification: QTL (quantitative trait loci) is the chromosomal site at which a group of genes affecting quantitative traits is located. Example: height, weight etc.

3. Which of the following factor does not contribute to quantitative traits?
A. Polygenes
B. Environmental
C. Genetic
D. Carbohydrate content
Answer: D
Clarification: Quantitative inheritance is more complex inheritance than Mendelian inheritance as these are influenced by polygenes, genetic factors, and environmental factors.

4. Who explained the multifactorial hypothesis?
A. Ronald Fisher
B. Darwin
C. Mendel
D. Nilsson-Ehle
Answer: A
Clarification: Fisher hypothesis states that a particular trait is the result of the combined influence of genetic and environmental factors.

5. Which of the following describes the dissimilarity in the traits due to the variation in genetic factors?
A. Polygenic
B. Heritability
C. Quantitative trait loci
D. Maternal effect
Answer: B
Clarification: Heritability is a concept of variation which arises due to genetic factors. Often, this term also used to show a resemblance of parents to their offsprings.

6. Which of the following describes the inheritance controlled by cytoplasmic genes?
A. Extranuclear inheritance
B. Heritability
C. Environmental factors
D. Complex trait
Answer: A
Clarification: The cytoplasmic inheritance arises due to plasma genes located in cell organelles. The first time evidence for the cytoplasmic inheritance was presented by coherence in Mirabilis jalapa.

7. Which of the following is NOT true for cytoplasmic inheritance?
A. Reciprocal cross is always different
B. Unequal contribution from male and female gametes
C. It follows a Mendelian pattern of inheritance
D. Do not show segregation for traits
Answer: C
Clarification: Plasma gene inheritance or cytoplasmic inheritance does not follow the Mendelian pattern of inheritance thus it comes under Non-Mendelian inheritance.

8. What is a petite mutant?
A. Defective mitochondrial function of yeast
B. Plastid function mutant
C. Dwarfism
D. Maternal effect genes
Answer: A
Clarification: Mutation responsible for the defective mitochondrial function, produce mutant yeast called petite mutant.

9. Which of the following is NOT the type of petite mutant?
A. Nuclear
B. Neutral
C. Suppressive
D. Polygene
Answer: D
Clarification: Petite mutant are of three types, one is a nuclear petite mutant, which has a nuclear gene mutation, second is a neutral petite mutant, which do not have mitochondrial DNA, and the third one is a suppressive petite mutant.

10. Name the effect which shows the determination of character by the genotype of a female parent?
A. Cytoplasmic male sterility
B. Probability
C. Random mating
D. Maternal effect
Answer: D
Clarification: The phenotype of the child would be determined by the genotype of the mother, such phenomenon is known as a maternal effect.

To practice all areas of Life Sciences Problems, .

Life Sciences Multiple Choice Questions on “RNA”.

1. Molecules which play the key role in the transfer of genetic information during protein synthesis are ___________
A. DNA
B. RNA
C. Nucleic acid
D. Lipids
Answer: B
Clarification: DNA has all the information which is confined to the nucleus, it is only transferred with the help of RNA during protein synthesis. RNA also has a diverse function in the body which includes the enzymatic activity of ribozyme and storage of genetic information in RNA viruses.

2. Double helix formed by RNA is more stable than DNA.
A. True
B. False
Answer: A
Clarification: The difference in their thermal stability is not clearly known but double-stranded helical RNA needs higher temperature for denaturation than DNA.

3. Which form of structure has been adopted by RNA?
A. A-form
B. B-form
C. Z-form
D. D-form
Answer: A
Clarification: Double helical track in RNA is generally short and formed by an A-form structure which differs from B-form adopted by DNA double helix.

4. Name the RNA molecules which is used to carry genetic information copied from DNA?
A. tRNA
B. mRNA
C. rRNA
D. snRNA
Answer: B
Clarification: Each type of RNA functions differently, among them mRNA which is also known as messenger RNA carries genetic information from DNA in the form of series of a three-base codon, which specifies the amino acid.

5. Which of the following RNA molecule convert information stored in the nucleic acid to protein?
A. mRNA
B. snRNA
C. rRNA
D. tRNA
Answer: D
Clarification: Transfer RNA (tRNA. plays a key role in protein biosynthesis and known as adapter tRNA. It acts as an interface between nucleic acid language and protein language. Additionally, it also participates in reverse transcription as a primer.

6. Name the secondary structure of tRNA?
A. Cloverleaf
B. L-shaped
C. Duplex
D. Triple Helix
Answer: A
Clarification: Based on their primary sequence tRNA folds into cloverleaf like secondary structure with well-defined loops and stems while tertiary structure further modified into the L-shaped structure.

7. Name the RNA molecule which takes part in the formation of the ribosome?
A. mRNA
B. tRNA
C. rRNA
D. gRNA
Answer: C
Clarification: rRNA is also known as ribosomal RNA which is a key component in the formation of a ribosome. rRNA molecules along with the ribosomal proteins in the nucleolus form pre-ribosomal subunit 40S and 60S respectively.

8. Which of the following rRNA molecules have peptidyl transferase activity in prokaryotes?
A. 23S rRNA
B. 28S rRNA
C. 5S rRNA
D. 18S rRNA
Answer: A
Clarification: rRNA molecules have several roles in protein synthesis, one of them is peptidyl transferase activity. In prokaryotes, 50 subunit has 23S rRNA which has a catalytic role and forms a part of peptidyl transferase activity. Similarly, eukaryotes have 28S rRNA in 60 subunits.

9. Which of the following statement is Incorrect about SnRNA?
A. It is small nuclear RNA
B. It helps in RNA splicing
C. It is also called snurps
D. It functions in RNA editing
Answer: D
Clarification: SnRNA is small nuclear RNA mainly found in the nucleus of eukaryotic cells. It takes part in RNA splicing and always remain associated with other proteins and referred to as snurps or snRNP. It functions in RNA editing is incorrect as RNA editing is done by guide RNA.

10. What is the role of snoRNA in eukaryotes?
A. Chemical modification
B. RNA splicing
C. Act as adaptor RNA
D. Forms component of the ribosome
Answer: A
Clarification: snoRNA takes part in chemical modification like methylation of rRNA and other forms of RNA in eukaryotes. It forms a snoRNP complex with the proteins and guides it to the modification site of RNA.

11. Name the class of RNA which takes part in RNA Editing?
A. snRNA
B. tRNA
C. gRNA
D. SiRNA
Answer: C
Clarification: gRNA is guide RNA which is an RNA gene that functions in RNA editing. It was reported in mitochondria of kinetoplastids, where mRNA edited by inserting or deleting stretches of uridylates.

.