This set of Molecular Biology Multiple Choice Questions & Answers (MCQs) focuses on “The Central Dogma Outlines the Flow of Genetic Information”.
1. Who were the first to suggest that one strand of DNA might act as a template for the synthesis of its complementary strand?
a) Meselson and Stahl
b) Watson and crick
c) Walter Flemming
d) Rosalind Franklin and Maurice Wilkins
Explanation: In Watson and Crick’s paper on the model of DNA double helix they ended with a statement that it had not escaped their notice that the specific pairing they had postulated immediately suggested that one strand might be the template for the complementary strand synthesis.
2. Semiconservative nature of replication of eukaryotic chromosome was first demonstrated by _______
a) Walter Flemming on root tip cells of Vicia faba
b) J. Herbert Taylor, Philip Wood and Walter Hughes on root tip cells of Vicia faba
c) Walter Flemming on root tip cells of Phaseolus vulgaris
d) J. Herbert Taylor, Philip Wood and Walter Hughes on root tip cells of Phaseolus vulgaris
Explanation: as Walter Flemming discovered cell division not semi conservative nature of replication. Semiconservative nature of replication was first demonstrated by J. Herbert Taylor, Philip Wood and Walter Hughes on root tip cells of broad bean which is the common name for Vicia faba.
3. Watson and Crick’s suggestion of the complementary strand synthesis taking one of the parent strand as template was proposed in _________
Explanation: As Watson and Crick’s paper on structure of DNA was published in 1953 they ended their journal suggesting the possibility of the synthesis of complementary strand taking one of the parent strands as the template.
4. Which of the following statements is true with respect to the DNA double helix?
a) Composed of two or more polynucleotide chains
b) The base pairs have opposite polarity
c) Covalent bond exists in base pairing
d) T is transcribed as U
Explanation: The two strands having complementary base pairing have the same helical geometry but have opposite polarity. This is because the strands are held together are antiparallel in nature.
5. Who, in which year showed firm enzymological proof that DNA alone functions as the template for the synthesis of new DNA strands?
a) Watson and Crick in 1953
b) Avery, MacCarty and Macleod in 1944
c) Meselson and Stahl in 1958
d) Hershey and Chase in 1952
Explanation: Within five years of the discovery of the double helix, evidence emerged for the separation of the complementary strands during DNA replication as suggested by Watson and Crick. This firm enzymological proof was first provided by Meselson and Stahl’s experiment of Semiconservative way of replication of DNA in 1958.
6. Replication of DNA ends are carried out by polymerase.
Explanation: Replication of DNA ends, that is, the telomeres cannot be done using polymerases. Cell has a unique enzyme, telomerase which uses its own unique mechanism for telomere replication.
7. Which of the following regarding the basic mechanism of gene expression is correct?
a) DNA ―> tRNA―> protein
b) RNA ―> cDNA ―> mRNA―> protein
c) RNA ―> DNA―> mRNA ―> protein
d) DNA ―> protein
Explanation: Gene expression is carried forward from DNA to mRNA (transcription) and mRNA to protein (translation). To this RNA can be converted to cDNA by reverse transcription. Then the process is carry forwarded in the same manner.
8. Which of the following does not take part in gene expression?
c) RNA processing
Explanation: Replication is the coping of the gene in double but plays no role in the production of protein thus, expression of gene. Transcription is the production of RNA from DNA and RNA processing is used for stabilizing the RNA in cytosol ad excision of non-coding regions. Translation is the major process which leads to the formation of polypeptide chain.
9. Multiple copies of RNA could be formed at the same time.
Explanation: The RNA produced does not remain base paired to the template DNA strand and is displaced only by a few nucleotides behind the transcription site. Thus another RNA polymerase can attach itself to the DNA template facilitating multiple RNA production.
10. Amino acids prior to their incorporation into polypeptide must be attached to a special adaptor molecule. Who proved this and when?
a) Francis H. Crick in 1955
b) Paul C. Zamecnic and Maholon B. Hoagland in 1957
c) James Watson and Francis H. Crick in 1953
d) Linus Pauling in 1950
Explanation: In 1955 Francis H. Crick proposed that prior to the incorporation of amino acids in polypeptide chain they must be attached to an adapter molecule which can interact with the three-nucleotide long coding units of mRNA. This was finally proved in 1957 by Paul C. Zamecnic and Maholon B. Hoagland. They demonstrated that amino acids were carried by the transfer RNAs (tRNA) to the ribosome for its transfer to the growing polypeptide chain.
Sanfoundry Global Education & Learning Series – Molecular Biology.
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