All Free Biology MCQs with Answers

• A. Enzyme
• B. Protein
• C. Polypeptide
• D. Polysaccharide

Explanation: The more accurate statement is that "one gene typically encodes for one polypeptide." This concept is known as the one gene-one polypeptide hypothesis, proposed by George Beadle and Edward Tatum based on their work with Neurospora crassa in the mid-20th century. It suggests that the function of a gene is to dictate the production of a specific polypeptide chain.

• A. Vernon Ingram
• B. Sanger
• C. P.A. Levene
• D. F. Miescher

Explanation: The sequence of amino acids in insulin molecules was determined by Frederick Sanger in the early 1950s. Sanger developed the first method for sequencing proteins, which he used to determine the precise sequence of amino acids in insulin. His groundbreaking work earned him the Nobel Prize in Chemistry in 1958. Sanger's method, known as the Sanger sequencing method or chain-termination method, revolutionized the field of molecular biology and laid the foundation for many subsequent advances in genetics and protein biochemistry.

• A. Vernon Ingram
• B. Herrick
• C. P.A. Levene
• D. F. Miescher

Explanation: While Vernon Ingram made significant contributions to the understanding of sickle cell anemia, he did not discover the condition. Sickle cell anemia was first described by James B. Herrick, an American physician, in 1910. Herrick reported a case of anemia in a patient of African descent whose red blood cells appeared sickle-shaped under the microscope.

• A. Histidine
• B. Leucine
• C. Valine
• D. Proline

Explanation: Sickle cell anemia is caused by a specific point mutation in the gene that encodes the beta-globin subunit of hemoglobin. In this mutation, the amino acid glutamic acid is substituted with valine at position 6 of the beta-globin chain. So, the correct answer is that in sickle cell anemia, glutamic acid is changed to valine.

• A. Protein
• B. DNA
• C. mRNA
• D. All of the above

Explanation: The Central Dogma of molecular biology outlines the unidirectional flow of genetic information from DNA to RNA and then to protein. It states that genetic information is transcribed from DNA to mRNA and translated from mRNA to protein, representing the core process of gene expression.

• A. Replication
• B. Transcription
• C. Translation
• D. None of the above

Explanation: The synthesis of protein, a fundamental process in biology, is termed translation. During translation, the genetic information encoded in mRNA is decoded by ribosomes, leading to the assembly of amino acids into polypeptide chains according to the sequence specified by the mRNA.

• A. Transcription
• B. Replication
• C. Translation
• D. None of the above

Explanation: The synthesis of RNA from DNA is called transcription. During transcription, an RNA polymerase enzyme binds to a specific region of DNA called the promoter, and it catalyzes the synthesis of a complementary RNA molecule using one strand of the DNA as a template.

• A. mRNA
• B. rRNA
• C. tRNA
• D. None of the above

Explanation: Anticodons are present on transfer RNA (tRNA) molecules. These specialized RNA molecules play a crucial role in protein synthesis by carrying specific amino acids to the ribosome and ensuring that they are incorporated into the growing polypeptide chain in the correct sequence.

• A. mRNA
• B. rRNA
• C. tRNA
• D. None of the above

Explanation: In the context of molecular biology and genetics, "codes" typically refer to codons. Codons are sequences of three nucleotides (triplets) found on mRNA molecules. These codons serve as the genetic code that specifies particular amino acids during protein synthesis. Each codon corresponds to a specific amino acid or a start or stop signal.

• A. Leading strand
• B. Antisense strand
• C. Sense strand
• D. Lagging strand

Explanation: During transcription, the strand of DNA that serves as the template for RNA synthesis is called the antisense strand or the noncoding strand. This strand is also known as the template strand. Transcription occurs in the 5' to 3' direction along this template strand, and the RNA transcript that is produced is complementary to this template strand.