DNA, RNA & Protein Synthesis MCQ Quiz - Objective Question with Answer for DNA, RNA & Protein Synthesis - Download Free PDF

The Correct answer is Hydrogen bonding.

Key Points

• In DNA, the two complementary strands are held together by hydrogen bonds between the nitrogenous bases.
• Adenine (A) always pairs with Thymine (T) through two hydrogen bonds, while Guanine (G) pairs with Cytosine (C) using three hydrogen bonds.
• This specific pairing is known as complementary base pairing, which is essential for the accurate replication of genetic material.
• Hydrogen bonds are weak, non-covalent interactions that allow the double helix structure of DNA to unzip during replication and transcription.
• Although individually weak, the cumulative effect of a large number of hydrogen bonds provides structural stability to the DNA double helix.
• The double helix model of DNA was first proposed by James Watson and Francis Crick, and their discovery highlighted the role of hydrogen bonding in maintaining DNA’s structural integrity.
• These bonds ensure that mutations are minimized by enabling specificity in base pairing during DNA replication.
• Hydrogen bonding occurs due to the difference in electronegativity between the hydrogen atom and the electronegative atoms (e.g., oxygen or nitrogen) involved in the base pairs.

 Additional Information

• Ionic bonding
  • Ionic bonds occur due to the electrostatic attraction between oppositely charged ions, which is not relevant in the context of DNA base pairing.
  • Examples of ionic bonding are typically found in compounds like sodium chloride (NaCl).
  • In DNA, ionic interactions are involved in the stabilization of the double helix through interactions between the negatively charged phosphate backbone and positively charged ions, but they are not responsible for base pairing.
• Van Der Waals interactions
  • Van Der Waals forces are weak, short-range forces that arise from fluctuating dipoles, contributing to DNA’s overall structural stability.
  • These interactions are present between stacked bases in the DNA double helix, known as base stacking interactions, but they do not play a direct role in base pairing.
• Covalent bonding
  • Covalent bonds involve the sharing of electron pairs between atoms, and they are responsible for the formation of the sugar-phosphate backbone in DNA.
  • These bonds are much stronger than hydrogen bonds and provide the primary structure of DNA, but they do not mediate base pairing.

The Correct answer is Synthesise new DNA strands complementary to the template.

Key Points

• DNA polymerase is a key enzyme involved in the process of DNA replication.
• Its primary function is to catalyse the addition of nucleotides to the growing DNA strand, ensuring it is complementary to the original template strand.
• The enzyme works in the 5’ to 3’ direction, adding new nucleotides to the free 3’-OH group of the preceding nucleotide.
• DNA polymerase requires a template strand and a primer to initiate synthesis.
• This enzyme plays a critical role in maintaining the accuracy and fidelity of DNA replication by performing proofreading and correcting errors.
• DNA polymerase is essential for cell division as it ensures that genetic information is accurately passed to daughter cells.
• Replication of DNA is crucial for processes such as growth, repair, and reproduction in living organisms.
• There are different types of DNA polymerase enzymes, including DNA polymerase I, II, and III in prokaryotes and DNA polymerase alpha, beta, delta, and epsilon in eukaryotes, each specialized for different functions.

Additional Information

• Ligate Okazaki fragments together
  • This function is performed by the enzyme DNA ligase, not DNA polymerase.
  • Okazaki fragments are short DNA sequences synthesized on the lagging strand during replication.
  • DNA ligase joins these fragments by forming phosphodiester bonds between adjacent nucleotides.
• Unwind the DNA double helix
  • This process is carried out by the enzyme helicase, not DNA polymerase.
  • Helicase breaks the hydrogen bonds between complementary base pairs, allowing the two strands of DNA to separate and serve as templates.
• Remove RNA primers from the lagging strand
  • The removal of RNA primers is performed by enzymes such as DNA polymerase I in prokaryotes and RNase H in eukaryotes.
  • DNA polymerase I also replaces the RNA primers with DNA nucleotides after their removal.

The correct answer is Hydrogen bonding potential based on base specificity.

Key Points

• The term "complementary" in DNA refers to the ability of nucleotide bases to pair specifically through hydrogen bonding, ensuring accurate replication and transcription.
• Adenine (A) pairs with Thymine (T) via two hydrogen bonds, while Cytosine (C) pairs with Guanine (G) via three hydrogen bonds.
• Complementary base pairing is guided by Chargaff's Rule, which states that the amount of A equals T, and the amount of C equals G in double-stranded DNA.
• This property is essential for the double-helix structure of DNA, where the two strands run antiparallel to each other.
• Complementary base pairing ensures genetic fidelity, allowing DNA to serve as a template for replication and RNA synthesis.

Additional Information

• Nucleotide Structure: Each nucleotide consists of three components: a phosphate group, a sugar molecule (deoxyribose in DNA), and a nitrogenous base (A, T, C, G).
• Antiparallel Orientation: DNA strands run in opposite directions, 5' to 3' and 3' to 5', allowing complementary base pairing.
• Hydrogen Bonding: These weak bonds stabilize the double-helix structure while allowing strand separation during replication and transcription.
• Chargaff's Rule: This rule provides the foundation for complementary base pairing, ensuring equal proportions of A-T and C-G pairs in double-stranded DNA.
• DNA Replication: Complementary base pairing enables each strand of DNA to act as a template for the synthesis of a new strand, ensuring accurate genetic transfer.

The correct answer is option 3.

Key Points

• Human insulin was the first hormone to be produced using recombinant DNA technology. Hence, option 3 is correct.
• It was developed by Genentech and Eli Lilly in the early 1980s, marking a major breakthrough in biotechnology and medicine.
• This synthetic insulin is called "Humulin", and it is produced by inserting the human insulin gene into E. coli bacteria, which then synthesize insulin.

The Correct answer is mRNA.

Key Points

• mRNA stands for messenger RNA.
• It is responsible for transporting genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm, where protein synthesis occurs.
• During the process of transcription, DNA is used as a template to produce mRNA.
• The sequence of nucleotides in mRNA corresponds to the sequence of amino acids in a protein, following the rules of the genetic code.
• mRNA carries codons, which are specific sequences of three nucleotides that code for a particular amino acid.
• It plays a crucial role in the process of translation, where ribosomes decode the mRNA to synthesize proteins.
• mRNA has a short life span in the cell, as it is degraded after the protein synthesis process is complete.
• Its primary role is to act as an intermediary between the genetic material (DNA) and the machinery responsible for protein production.

 Additional Information

• tRNA
  • tRNA stands for transfer RNA.
  • It plays a role in translation by bringing specific amino acids to the ribosome based on the codons in the mRNA.
  • Each tRNA has an anticodon that pairs with a complementary codon on the mRNA.
• snRNA
  • snRNA stands for small nuclear RNA.
  • It is primarily involved in the process of splicing during the maturation of pre-mRNA in the nucleus.
  • snRNAs are a component of spliceosomes, which remove introns from pre-mRNA.
• rRNA
  • rRNA stands for ribosomal RNA.
  • It is a structural and functional component of ribosomes, which are the sites of protein synthesis.
  • rRNA helps to catalyze the formation of peptide bonds between amino acids during translation.

The correct answer is 

Key Points

• A nucleotide is the basic building block of nucleic acids, such as DNA and RNA.
• Each nucleotide in DNA consists of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases:
  • Adenine (A)
  • Guanine (G)
  • Cytosine (C)
  • Thymine (T)
• Polynucleotides are long chains of these nucleotides.

Additional Information

• The backbone of a DNA is made up of repeating units of deoxyribose sugar, nitrogenous base and phosphate group which occur alternately.
• The phosphate group attaches to the -OH group at the 5' carbon of the deoxyribose sugar through a phosphodiester linkage.

Correct answer: 1)

Concept:

• The synthesis of protein is known as translation.
• It takes place in the cytoplasm of the cell.
• The machinery for translation includes- transfer RNA (tRNA), messenger RNA (RNA), ribosomal RNA (rRNA), and different enzymatic factors.

Explanation:

• Option 1: Small interfering RNA (siRNA) are double-stranded RNA molecules that inhibit the translation of specific mRNA.
• They do not participate in protein synthesis.
• Option 2: DNA is transcribed into mRNA that serves as a template for protein synthesis.
• It is single-stranded and contains a sequence of nucleotides that codes for amino acids.
• A triplet of nucleotide forms a codon and each codon codes for a single amino acid.
• Option 3:
• Transfer RNA (tRNA) brings amino acids to the ribosomes during protein synthesis.
• Specific tRNA is there for specific amino acids.
• Option 4: Ribosomes are made up of rRNA which is essential for protein synthesis.

So, the correct answer is option 1. 

• Proteins are made up of Amino Acids, essentially they are the building blocks of proteins.
• Each protein is made from a combination of different amino acids
• There are about 21 amino acids in total.
• Each acid is made up of carbon, hydrogen, oxygen and nitrogen although other elements might also be present in different acids.

Additional Information 

The correct option is 3 that is gene mapping.

Concept:

Animal and plant cell nuclei contain thread-like structures called chromosomes. Deoxyribonucleic acid (DNA), which is transmitted from parents to children during reproduction, is only one of the two components of each chromosome.

The precise instructions that give each sort of living thing its individuality are found in DNA.

Explanation:

• A method for locating a gene's locus and measuring the distances between genes is called gene mapping.
• Gene mapping is used to identify the linear arrangement of genes and how far apart they are from one another on the same chromosome.
• The terms "genome walking" and "chromosome walking" are used to locate unknown DNA sequences next to recognized sequences, although they have nothing to do with locating genes on chromosomes.

• Genes are the units located in the chromosomes of a cell.
• It is a unit of DNA on a chromosome which governs the synthesis of one protein that controls specific characteristics of an organism.
• Genes are composed of deoxyribonucleic acid (DNA), except in some viruses, which have genes consisting of ribonucleic acid (RNA).
• Every human cell contains 23 pairs of chromosomes, for a total of 46 chromosomes.
• Lysosomes are also known as suicidal bags.

The term ‘allele’ comes from ‘allelomorph’ and refers to the different forms of a gene that affect an organism's phenotype or appearance.

Key Points

• The number of allelic forms of a gene may be many in a population, but since each organism has only one pair of homologous chromosomes of a kind, only two of its variants are present in an organism.
• Various interactions may occur between alleles of the same genes or alleles of different genes, which give rise to different phenotypes, making the inheritance patterns complex.
  • Recessive allele - The allele which is masked or remains unexpressed is called recessive. 
  • Dominant Allele - The allele that completely masks the expression of other alleles is dominant.
  • Codominance- It is a phenomenon in which both the alleles are completely expressed in the heterozygous condition, the phenotype of the heterozygous individual is a mixture of both.
• A combination of different types of alleles influences the inheritance pattern in an individual organism.

Hence, the allele is a pair of genes that occupy a specific location on a particular chromosome and control the same trait.

Important Points

• Karyotype - It is an individual’s complete set of chromosomes or laboratory-produced image of a person’s chromosomes isolated from an individual cell and arranged in numerical order that is used to look for abnormalities in chromosome number or structure.
• RNA - It refers to the Ribo-nucleic acid present in the cells of organisms having a structure similar to DNA.
• Autosomes - The 22 pairs of non-sex chromosomes present in the nucleus of an individual.

• Histones are a set of positively charged, basic proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes.
• A protein acquires charge depending upon the abundance of amino acids residues with charged side chains.
• Histones are rich in the basic amino acid residues lysines and arginines. Both the amino acid residues carry positive charges in their side chains.
• Histones are organized to form a unit of eight molecules called Histone octamer.

​Extra Information :

• Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) are the two types of nucleic acids found in living systems.
• DNA acts as the genetic material in most of the organisms.
• RNA though it also acts as genetic material in some viruses, mostly functions as a messenger.

The correct answer is a, b, and d.

Concept:

DNA replication

• DNA replication occurs in all living organisms.
• It is an important biological process for inheritance.
• It is an enzyme-catalyzed reaction.
• The main enzyme in the DNA replication process is DNA Polymerase.
• A DNA molecule replicates itself to create two identical copies.

Explanation:

DNA replication is a semi-conservative process (correct)

• Watson and Crick in 1953 proposed a scheme that DNA replication was semi-conservative.
• Replication is semi-conservative because the two parental strands separate and each strand acts as a template for synthesizing a complementary strand over it.
• After completion of replication, each DNA had one parental strand and one newly synthesized strand.

DNA replication is a semi-discontinuous process (correct)

• DNA replication is a semi-discontinuous process because two complementary strands are synthesized during replication and run anti-parallel. 
• The DNA polymerase can only add nucleotides to the 3' end of a DNA strand.
• As a result, one strand is synthesized continuously, known as the leading strand, and the other is synthesized discontinuously, known as the lagging strand.

DNA polymerase III is responsible for the replacement of the primer sequence of the Okazaki fragments (incorrect)

• DNA polymerase III synthesizes a new DNA strand in 5'→3' direction, antiparallel to the template strand.
• DNA polymerase I remove RNA primer nucleotides with its  5'→3' exonuclease activity and replaces them with complementary DNA nucleotides by its 5'→3' polymerisation activity.

Primer is synthesized on both the strands of the DNA (correct)

• Before DNA replication can occur, a primer must be synthesized by an enzyme called primase, which is a type of RNA polymerase. 
• Because the enzymes that synthesize DNA, known as DNA polymerases, can only attach new DNA nucleotides to an existing strand of nucleotides, the synthesis of a primer is required.