All Free Biology MCQs with Answers
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19844 questions · page 746 of 1985
7451. If an organism has a diploid number of 36, what is its haploid number?
- A. 12
- B. 9
- C. 18
- D. 22
Explanation: The haploid (n) number of chromosomes is the number of chromosomes found in a gamete of a reproductive cell. This number is half of the diploid (2n) number. Half of 36 is 18.
Correct answer: 187452. The DNA formed by the reverse transcription is called:
- A. rDNA
- B. dDNA
- C. cDNA
- D. DNA
Explanation: This option is the correct answer. cDNA stands for complementary DNA. It is the DNA molecule synthesized from an RNA template by the process of reverse transcription. Reverse transcription involves the synthesis of a complementary DNA strand using an RNA template and the enzyme reverse transcriptase. The resulting cDNA represents a copy of the RNA sequence.
Correct answer: cDNA7453. Which of the following combination of base pair is absent in DNA?
- A. A-T
- B. C-G
- C. A-U
- D. T-A
Explanation: In RNA, the two pyrimidine bases are uracil and cytosine. While in DNA, the pyrimidine bases are thymine and cytosine. Thus, uracil is absent in DNA and is replace by thymine.
Correct answer: A-U7454. If the genetic code is made up of three nucleotides, then total possible genetic codes will be
- A. 4
- B. 20
- C. 64
- D. 61
Explanation: Each group of three nucleotides encodes an amino acid. The total number of genetic codes can be found by 4^3 = 64, where 4 is the total number of nucleotide bases and 3 is the number of bases that can be in one genetic code.
Correct answer: 647455. Phenylketonuria is an example of:
- A. Polyploidy
- B. Transmutation
- C. Inversion
- D. Point mutation
Explanation: Phenylketonuria is characterized by a mutation causing the loss of function of the hepatic enzyme phenylalanine hydroxylase through a mutation in the genome. Point mutation occurs when one base pair has been altered, added, or deleted from DNA or RNA. Hence, Phenylketonuria is an example of point mutation.
Correct answer: Point mutation7456. The mutation which causes change in the sequence of DNA at a given position is called:
- A. Point mutation
- B. Chromosomal mutation
- C. Translocation
- D. Inversion
Explanation: Point mutation is the phenomenon that occurs when a single nucleotide is added, altered, or deleted from an organisms genome. It alters the sequence of DNA.
Correct answer: Point mutation7457. The process of DNA replication in which each strand acts as a template for new double helix, composed of one parental strand and one newly polymerized strand refers:
- A. PCR
- B. Semi-conservative model
- C. Conservative mode
- D. Both
Explanation: DNA replication is a semi-conservative process. In this model, the two strands of DNA unwind from each other, and each acts as a template for the synthesis of a new, complementary strand. This results in two DNA molecules with one original strand and one new strand.
Correct answer: Semi-conservative model7458. The process in which an RNA copy of the DNA sequence encoding the gene is produced:
- A. Translation
- B. Transcription
- C. Polymerization
- D. Genesis
Explanation: Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). DNA safely and stably stores genetic material in the nuclei of cells as a reference or template.
Correct answer: Transcription7459. DNA polymerase III adds nucleotides to DNA strand, replication always proceeds from:
- A. 3' → 5'
- B. 5' → 3
- C. Sometime "3' → 5' & "5' → 3' "
- D. None of the given options
Explanation: DNA replication occurs in the 5' to 3' direction. DNA polymerase can only add nucleotides the 3' -OH group of the growing DNA strand, this is why DNA replication occurs only in the 5' to 3' direction.
Correct answer: 5' → 37460. In translation, the termination codon is:
- A. UAA
- B. UCG
- C. AUG
- D. UUU
Explanation: Translation is the process by which a cell makes proteins using the genetic information carried in messenger RNA (mRNA). The codons that cause the termination of protein synthesis are known as stop/terminator codons. The DNA stop codons are TAG, TAA, and TGA. The corresponding RNA, stop codons are UAG, UAA, and UGA. AUG is the most common start codon and it codes for amino acid methionine.
Correct answer: UAA