All Free Biology MCQs with Answers
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19844 questions · page 741 of 1985
7401. In sexual reproduction, sex cells contain _ chromosomes when compared to other cells of the body
- A. same
- B. half
- C. double
- D. all of the above
Explanation: The sex cells are formed as a result of meiosis(reduction division) which causes the original normal chromosome number of the cell (2n) to be divided to become half (n)
Correct answer: half7402. Identify purine and pyrimidines from the following figures
- A. A and B are purines, and C, D, and E are pyrimidines.
- B. D and B are purines, and C, A, and E are pyrimidines
- C. A and E are purines, and C, D, and B are pyrimidines.
- D. A and C are purines, and B, D, and E are pyrimidines.
Explanation: Purines are those bases that are double-ringed. Pyrimidines have a single ring. As we can see, A and C are double-ringed so they are purines. On the other hand, B, E, and D are single rings so they are pyrimidines.
Correct answer: A and C are purines, and B, D, and E are pyrimidines.7403. A strand, almost _ nucleotides long is wrapped around a core of _ histone proteins to form a structure called a Nucleosome.
- A. 200 - 4
- B. 200 - 8
- C. 200 - 16
- D. 200 - 40
Explanation: A strand of 200 nucleotides long are wrapped twice around a core of eight histone proteins to form a structure called a nucleosome. The histone octamer at the centre of the nucleosome is formed from two units each of histones H2A, H2B, H3, and H4.
Correct answer: 200 - 87404. Pick the odd one out in the following picture.
- A. A
- B. B
- C. C
- D. D
Explanation: This picture has all requirements (tRNA,mRNA, and ribosome) for the protein synthesis (translation) to happen except RNA polymerase, which is a tool required for transcription, not for translation.
Correct answer: C7405. An enzyme is responsible for copying a DNA sequence into an RNA sequence.
- A. Restriction enzyme
- B. Reverse transcriptase.
- C. RNA polymerase
- D. DNA polymerase
Explanation: RNA polymerase carries out the function to copy the DNA sequence into an RNA sequence.A restriction enzyme is used to cleave the DNA at the ends. Reverse transcriptase is used to synthesize DNA from RNA.DNA polymerase forms DNA strands by joining bases together.
Correct answer: RNA polymerase7406. Read the code mentioned in the following picture and arrange the sequence of all five codons in which Leucine is at 3rd position. while isoleucine is in 4th position. Keep in mind that CUU is the code for Leucine, AUU for Isoleucine and CAA or glutamine.
- A. UAA-AUG-CAA-CUU-AUU
- B. AUG-CAA-CUU-AUU-UAA
- C. AUU-AUG.CAA.CUU-UAA
- D. AUG-UAA -CUU-AUU.CAA
Explanation: AUG-CAA-CUU-AUU-UAA is most appropriate because it starts with a start codon and ends with a stop codon while having CUU and AUU at third and fourth positions respectively.
Correct answer: AUG-CAA-CUU-AUU-UAA7407. In semi-conservative replication, which of the following is true regarding the separation of two strands?
- A. Primary structure is conserved, and secondary structure is disturbed
- B. Secondary structure is conserved, and the primary structure is disrupted
- C. both the primary and secondary structures are conserved
- D. Both the primary and secondary structures are disrupted
Explanation: In semi conservative replication, the original molecule is unzipped; each strand of the duplex becomes a part of another duplex. During the separation of two strands, the primary structure is conserved while the secondary structure is disrupted.
Correct answer: Primary structure is conserved, and secondary structure is disturbed7408. Name the type of the following chromosome:
- A. Metacentric
- B. Submetacentric
- C. Telocentric
- D. Acrocentric
Explanation: A chromosome where the centromere is not central and is instead located near the end of the chromosome. Humans usually have five pairs of acrocentric autosomes (chromosomes 13, 14, 15, 21, 22).
Correct answer: Acrocentric7409. Which of the following is NOT true for a gene?
- A. A gene is a sequence of nucleotides in DNA.
- B. A gene is the basic unit of heredity.
- C. A gene codes for a molecule that has a function.
- D. A gene expresses to form chromosomes.
Explanation: All statements except D are correct. Genes do not express themselves to form chromosomes. Genes are small segments of DNA that join to form a whole chromosome.
Correct answer: A gene expresses to form chromosomes.7410. What are a and b in the following picture?
- A. Allele and allele
- B. Allele and gene
- C. Gene and gene
- D. Mutation and gene
Explanation: These are alleles for purple and white flowers. It can be confused as genes sometimes which is wrong because here we can see the two forms of a gene(variations of a gene), so allele is the more appropriate word here.
Correct answer: Allele and allele