All Free Biology MCQs with Answers

• A. T. H Morgan
• B. Griffith
• C. Walther
• D. Mendel

Explanation: Walther Flemming first observed chromosomes in 1879 during his studies on cell division (mitosis) using a light microscope.

• A. DNA and protein
• B. DNA and RNA
• C. RNA and lipids
• D. RNA and proteins

Explanation: A chromosome is composed primarily of DNA, proteins, and a small amount of RNA. The DNA carries genetic information in a double-helix structure, which is organized into functional units called genes. This DNA is tightly wrapped around proteins known as histones, forming nucleosomes, which help compact the DNA and organize it into chromatin. The chromatin further coils and condenses to form the structured, compact chromosome, especially during cell division. Additionally, some RNA molecules are associated with chromosomes, particularly in regions involved in the production of ribosomal RNA (rRNA). This highly organized structure enables chromosomes to efficiently store, protect, and transmit genetic information within the nucleus of a cell.

• A. Reduction in oxygen-carrying capacity of haemoglobin
• B. Linkage between the polypeptide chains in the haemoglobin molecule
• C. Single amino acid substitution in the haemoglobin molecule
• D. Viral infections of RNA viruses

Explanation: Sickle cell anemia is caused by a genetic mutation in the HBB gene, which provides instructions for making hemoglobin, the protein in red blood cells that carries oxygen throughout the body. This mutation leads to the production of an abnormal form of hemoglobin called hemoglobin S (HbS).

• A. DNA to Protein
• B. DNA to mRNA
• C. RNA to Protein
• D. DNA to tRNA

Explanation: Transcription is the first step, where DNA is used to synthesize messenger RNA (mRNA).

• A. Homochromatin
• B. Heterochromatin
• C. Semi-heterochromatin
• D. Semi-homochromatin

Explanation: Heterochromatin is the tightly packed form of DNA, making it less transcriptionally active.

• A. DNA
• B. Protein
• C. Both DNA and Protein
• D. Neither DNA nor Protein

Explanation: DNA carries genetic information and is responsible for inheritance.

• A. Osmotic pressure
• B. Hydrolic pressure
• C. Air pressure
• D. Mutation pressure.

Explanation: Mutation pressure refers to changes in the genetic code due to base substitutions, influencing evolution.

• A. 11
• B. 33
• C. 333
• D. 1

Explanation: In RNA, each codon is made up of three nucleotide bases, and each codon codes for a specific amino acid. So, if you delete a single base, it will result in a shift in the reading frame and potentially change the codons downstream from the deletion point. Therefore, a deletion at position 901 will affect 33 codons.

• A. tRNA
• B. mRNA
• C. rRNA
• D. All are present in same proportion.

Explanation: The most abundant RNA molecule in a cell is typically ribosomal RNA (rRNA). Ribosomal RNA is a type of RNA that plays a crucial role in the ribosome, which is the cellular machinery responsible for protein synthesis.

• A. Fungi
• B. Animals
• C. Bacteria
• D. Plants

Explanation: Spliceosomes help in the removal of introns. They will not occur in prokaryotes because prokaryotes do not have introns and thus, processing does not require splicing of mRNA. Spliceosomes are complex molecular machines found only in eukaryotic cells, including those of humans and other multicellular organisms. They are responsible for a crucial process in gene expression called RNA splicing.