All Free Biology MCQs with Answers

• A. Silver or Platinum
• B. Platinum or Zinc
• C. Silicon or Platinum
• D. Gold or Tungsten

Explanation: A gene or a biolistic particle delivery system, originally designed for plant transformation, is a device for injecting cells with genetic information. The payload is an elemental particle of a heavy metal such as gold or tungsten coated with plasmid DNA. The device is used to transform almost any type of cell including plants and is not limited to the genetic material of the nucleus. It can also transform organelles, including plastids.

• A. Disarming pathogen vectors.
• B. Transformation of plant cells.
• C. Constructing recombinant DNA by joining with vectors.
• D. DNA fingerprinting.

Explanation: Biolistics is a technique for introducing genetic material into living cells, especially plant cells, in which DNA-­coated microscopic particles (tungsten or gold particles) are bombarded with a very high velocity into the target cell using a special gun. The microprojectiles, typically 1mm in diameter, are accelerated to high velocity by a specially modified small calibre gun and penetrate the cell walls and plasma membrane with minimal damage. Hence, the novel DNA can be inserted into intact plant cells ultimately transforming it without using a vector.

• A. As selectable markers.
• B. To select healthy vectors.
• C. As sequences from where replication starts.
• D. To keep the cultures free of infection.

Explanation: Selectable markers are those genes which help in selecting those host cells which contain vectors (i.e., transformants) and eliminating the non­transformants. The genes encoding resistance to antibiotics such as tetracycline, ampicillin, kanamycin etc., are useful selectable markers. E.coli. Plasmid pBR322 has two resistance genes - ampicillin resistance (amp r) and tetracycline resistance (tet r) which are considered useful for selectable markers. The presence of restriction sites within the markers tet r and amp r permits an easy selection for cells transformed with the recombinant pBR322. Insertion of the DNA fragment into the plasmid using enzyme Pst I or Pvu I places the DNA insert within the gene amp r; this makes amp r nonfunctional. Bacterial cells containing such a recombinant pBR322 will be unable to grow in the presence of ampicillin but will grow on tetracycline. Similarly, when the restriction enzyme Bam HI or Sal I is used, the DNA insert is placed within the gene tet r making it nonfunctional. Bacterial cells possessing such a recombinant pBR322 will, therefore, grow on ampicillin but not on tetracyclin.

• A. B-­denaturation at a temperature of about 98°C separating the two DNA strands
• B. A-denaturation at a temperature of about 50°C
• C. C-extension in the presence of heat stable DNA polymerase
• D. A­-annealing with two sets of primers

Explanation: A schematic representation of PCR can be illustrated as follow.

• A. 5' - GAATTC ­- 3', 3' -­ CTTAAG ­- 5'
• B. 5' ­- CCAATG ­- 3', 3' ­- GAATCC ­- 5'
• C. 5' - CATTAG -­ 3', 3'­ - GATAAC ­- 5'
• D. 5' -­ GATACC ­- 3', 3' ­- CCTAAG ­- 5'

Explanation: Palindromes are groups of letters that form the same words when read both forward and backward, e.g., "MALAYALAM". As against a word­-palindrome where the same word is read in both directions, the palindrome in DNA is a sequence of base pairs that reads the same on the two strands when the orientation of reading is kept the same. For example, the following sequences read the same on the two strands in 5' -- 3' direction. This is also true if read in the 3' -- 5' direction. In this case, it is 5' - GAATTC - 3', 3'- CTTAAG - 5'.

• A. Replication completed
• B. Deletion mutation
• C. Start codon at the 5' end
• D. Palindromic sequence of base pairs

Explanation: Palindromes are groups of letters that form the same words when read both forward and backward, e.g., "MALAYALAM". As against a word­ palindrome where the same word is read in both directions, the palindrome in DNA is a sequence of base pairs that reads the same on the two strands when the orientation of reading is kept the same. For example, the following sequences read the same on the two strands in 5' -- 3' direction. This is also true if read in the 3' -- 5' direction. In this case, it is 5' - GAATTC - 3', 3' - CTTAAG - 5'.

• A. Colon
• B. Coelom
• C. Coenzyme
• D. Coli

Explanation: The enzyme restriction endonuclease EcoRI is found in the colon bacteria E.coli. So, here 'co' stands for coli. According to the nomenclature of restriction enzymes, the first letter used for the enzyme is the first letter of the genus name (in italics) of the bacterium, then comes the first two letters of its species (also in italics), next is the strain of the organism. At last is a Roman numeral signifying the order of discovery. Here, the enzyme EcoRI was isolated from the bacterium Escherichia coli (co), strain RY13(R) and it was the first endonuclease (I) isolated from E.coli.

• A. Spectrophotometry
• B. Tissue culture
• C. PCR
• D. Gel Electrophoresis

Explanation: In gel electrophoresis, DNA fragments separate (resolve) according to their size through the sieving effect provided by the agarose gel. Agarose is a natural polymer extracted from seaweeds and is commonly used as a matrix.

• A. Baculovirus
• B. Salmonella typhimurium
• C. Rhizopus nigricans
• D. Retrovirus

Explanation: Retroviruses in animals have the ability to transform normal cells into cancerous cells. We have transformed these pathogens into useful vectors for delivering genes of interest to humans. Retroviruses have been disarmed and are now used to deliver desirable genes into animal cells. So, once a gene or a DNA fragment has been ligated into a suitable retroviral vector it is transferred into a bacterial, plant or animal host (where it multiplies).

• A. Probe vector
• B. Probe
• C. Clone
• D. Plasmid

Explanation: Probes are single stranded, radiolabelled molecules of nucleic acids with known sequence. The probes having sequence complementary to the gene to be identified are supplied. They bind with the particular gene segment. Radiation imaging identifies the location of that particular segment which bind with probe. Probes are used as identification tool.