All Free Biology MCQs with Answers

• A. Overlapping
• B. Wobbling
• C. Degenerate
• D. Generate

Explanation: Certain amino acids are identified by more than one codon. Some amino acids are encoded by up to four codons, and amino acids, arginine and lysine are encoded by six codons. This is called code degeneracy.

• A. Ribosome synthesis
• B. Protein synthesis
• C. DNA synthesis
• D. RNA synthesis

Explanation: The process of translation is protein synthesis. Emil Fischer, a German chemist, established that proteins are polymers of amino acids. There are some twenty amino acids involved in protein synthesis. Translation is the fundamental process where a cell builds proteins by decoding messenger RNA (mRNA) instructions, using ribosomes and transfer RNA (tRNA) to link specific amino acids in the correct order, forming a polypeptide chain that becomes a functional protein, a crucial step in gene expression.

• A. Single stranded
• B. Double stranded
• C. Triple stranded
• D. Four stranded

Explanation: A DNA with unequal nitrogen bases would most probably be single-stranded. Nitrogenous bases are unequal in number in single-stranded DNA because they do not possess complementary base pairs.

• A. X-­ray crystallography
• B. Electron microscope
• C. Ultracentrifuge
• D. Light microscope

Explanation: Nucleotide arrangement in DNA can be seen by X­ray crystallography. Watson and Crick, in 1953, proposed the double-helical model for DNA. They were awarded the Nobel Prize in 1962. This model was developed by them based on several previous observations, including the X­ ray reflection studies of Franklin and Gosling in 1953.

• A. Escherichia coli
• B. Neurospora crassa
• C. Pneumococcus
• D. Drosophila melanogaster

Explanation: The experimental material in the study of DNA replication has been Escherichia coli. E. coli fully labelled with 1 N is allowed to grow in a 14N medium. The two strands of the DNA molecule of the first-generation bacteria have different densities and do not resemble their parent DNA. Meselson and Stahl, in 1958, by using 14 N and 15 N confirmed that the replication of DNA in E. coli is semi­conservative in nature.

• A. Transversion
• B. Transcription
• C. Translation
• D. Translocation

Explanation: The process in living cells in which the genetic information of DNA is transferred to a molecule of messenger RNA (mRNA) is the first step in protein synthesis. Transcription takes place in the cell nucleus or nuclear region and is regulated by transcription factors.

• A. Endosome
• B. Nucleosome
• C. Mesosome
• D. Centrosome

Explanation: An octamer of 4 histones complexed with DNA forms a nucleosome. The association of histones with DNA is very characteristic. It involves the formation of a linear array of spherical structures called nucleosomes. These structures contain four pairs of histones (H2A, H2B, H3 and H4) in a ball; around which is wrapped a stretch of about 150 base pairs of DNA.

• A. Monomer
• B. Dual polymer
• C. Single polymer
• D. Non-polymer

Explanation: DNA is a polymer made from four different monomers, called nucleotides. These join together in different combinations to make long strands. In a DNA molecule, two strands wrap around each other to form a double helix structure.

• A. 240 million
• B. 150 million
• C. 140 million
• D. 160 million

Explanation: A typical human chromosome contains 1.4x108 nucleotides in its DNA. The amount of information one chromosome contains would fill about 280 printed books of 1000 pages each if each nucleotide corresponds to a word and each page has 500 words on it.

• A. The condensed part of a chromosome
• B. In a closed configuration
• C. Never condensed
• D. In an open configuration

Explanation: Heterochromatin and euchromatin are 2 types of chromatin. The key difference between heterochromatin and euchromatin is the packaging. Heterochromatin is the highly packed form of chromatin, while euchromatin is the loosely packed form of chromatin. Euchromatin is in an open configuration. It represents the less condensed and more transcriptionally active regions of chromatin within a chromosome. Euchromatin allows for easier access to the genetic information contained in the DNA, making it available for gene expression and various cellular processes. In contrast, heterochromatin is the condensed part of a chromosome, and it is typically in a closed configuration, which is associated with gene silencing and a lack of active transcription.