All Free Biology MCQs with Answers
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19844 questions · page 739 of 1985
7381. What would be the number of nucleotides for a protein molecule of about 142 amino acids?
- A. 430
- B. 142
- C. 426
- D. 460
Explanation: Each amino acid is coded by 3 nucleotides, hence to form a protein molecule of 142 amino acids, 142 multiplied by 3 nucleotides would be needed, which comes out to be 426.
Correct answer: 4267382. The number of base pairs in a complete helical turn is/are:
- A. 1
- B. 5
- C. 10
- D. 15
Explanation: The distance between two corresponding base pairs is 0.34 nm and a complete helix measures 3.4 nm in length. So, the base pairs in a complete helix will be 10.
Correct answer: 107383. Evolutionary relationships among species are reflected in their _.
- A. DNA and proteins
- B. Only DNA
- C. Only proteins
- D. RNA
Explanation: Evolutionary relationships among species are reflected in their DNA and proteins, in their genes and gene products. If the sequences of monomers of genes and proteins of two species match closely, the sequence must have been copied from a common ancestor.
Correct answer: DNA and proteins7384. Within the chromosomes, each chromatid contains _ DNA molecule:
- A. One
- B. Two
- C. Three
- D. Half
Explanation: Even when a chromosome is replicated, it has two sister chromatids. Each sister chromatid has one DNA molecule. Overall, the chromosome has 2 DNA molecules in the replicated state but each chromatid still has only one DNA molecule.
Correct answer: One7385. Particular array of chromosomes that an individual processes is called its:
- A. Nucleosome
- B. Gene pool
- C. Karyotype
- D. Centromere
Explanation: Karyotyping is the process of pairing and ordering all the chromosomes of an organism, thus providing a genome-wide snapshot of an individual's chromosomes.
Correct answer: Karyotype7386. During DNA replication _ attaches the fragment to the lagging strand.
- A. Ligase
- B. Invertase
- C. Helicase
- D. Topoisomerase
Explanation: DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule
Correct answer: Ligase7387. The Meselson and Stahl experiment confirmed that DNA replicates in _ manner.
- A. Conservative
- B. Semi - conservative
- C. Dispersive
- D. New synthesis
Explanation: Each strand of original DNA serves as a template to form a new strand with one original and one replicated strand
Correct answer: Semi - conservative7388. In prokaryotes, only one type of RNA polymerase is present, while _ types of RNA polymerase are present in eukaryotes.
- A. Two
- B. Three
- C. Four
- D. Five
Explanation: All eukaryotes have three different RNA polymerases (RNAPs) which transcribe different types of genes
Correct answer: Three7389. Genetic code is a _ code and out of 64 codons, _ are nonsense codons.
- A. Single ; two
- B. Single ; three
- C. Triplet ; two
- D. Triplet ; three
Explanation: The genetic code has a triplet base. Nonsense codons are those that terminate the translation process since there are no corresponding tRNA molecules with anticodons for them. Genetic code is a degenerate code, meaning that multiple codons can code for the same amino acid. Out of the 64 codons, 3 of them are nonsense codons or stop codons. These stop codons (UAA, UAG, and UGA in the standard genetic code) do not code for any amino acid but instead signal the termination of protein synthesis.
Correct answer: Triplet ; three7390. Which of the following can be blocked, if one wants to stop translation of mRNA?
- A. RNA polymerase
- B. Helicase
- C. Elongation factor
- D. Primase
Explanation: mRNAs are usually translated by a series of ribosomes, spaced at intervals of about 100 to 200 nucleotides.Elongation factors are a group of proteins involved in various cellular processes, primarily in protein synthesis during translation. Their primary function is to facilitate the elongation phase of translation, where amino acids are added to the growing polypeptide chain.One of the key elongation factors in translation is called elongation factor
Correct answer: Elongation factor