Test: DNA, RNA & Experiments on Genetic Material


15 Questions MCQ Test Biology Class 12 | Test: DNA, RNA & Experiments on Genetic Material


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Attempt Test: DNA, RNA & Experiments on Genetic Material | 15 questions in 15 minutes | Mock test for NEET preparation | Free important questions MCQ to study Biology Class 12 for NEET Exam | Download free PDF with solutions
QUESTION: 1

Who among the following scientists had no contribution in the development of the double helix model for the structure of DNA?

Solution: Meselson and Stahl prove experimentally semi conservation of DNA replication not say but structure of DNA.
QUESTION: 2

DNA has genetic properties was revealed for the first time by

Solution: Avery, MacLeod and Mcarty conclude DNA is heridatary material first time while Griffith show transforming principal.
QUESTION: 3

The beginning of understanding genetic transformation in bacteria was made by

Solution:

Transformation was discovered in Streptococcus pneumoniae in 1928 by Frederick Griffith; in 1944, Oswald T. Avery, Colin M. MacLeod, and Maclyn McCarty demonstrated that the “transforming principle” was DNA. Both results are milestones in the elucidation of the molecular nature of genes.

QUESTION: 4

DNA contains nucleobases, sugar and phosphate. Removal of which among these from a DNA sample will not significantly affect the length of DNA?

Solution: Nucleobases, also known as nitrogenous bases  are nitrogen-containing biological compounds that form nucleosides, which in turn are components of nucleotides, with all of these monomersconstituting the basic building blocks of nucleic acids. The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)....
QUESTION: 5

According to Chargaff’s rule, which one is correct?​

Solution:

According to Chargaff’s rule in all cellular DNA, regardless of the species, number of adenosine residues is equal to the number of thymidine residues which means that A = T and the number of guanosine residues is equal to the number of cytidine residues; G = C . Hence, that the sum of the purine residues equals the sum of the pyrimidine residues; i.e., A + G = T + C.

QUESTION: 6

Whose experiments cracked the DNA and discovered unequivocally that a genetic code is a triplet?

Solution:
The existence of a triplet code was simply an assumption till 1961 when Nirenberg and Methaei proved its existence by experiment. They were able to synthesise artificial mRNA, which contained only one nitrogenous base, ie, uracil. This synthetic poly-U sequence was then placed in a cell-free system containing protein synthesizing enzymes (extracted from bacterium E. coil) and 20 amino acids together with necessary ATP. During the process, a small polypeptide molecule was produced, which was formed by the linking of phenylalanine. This issuggested that UUU is code for phenylalanine. Nirenberg got Nobel Prize for his contributions.
QUESTION: 7

In Hershey and Chase experiments, radioactive 32P was used to culture bacteriophages which resulted in radioactive

Solution:

In Hershey and Chase experiment, some bacteriophage viruses where grown in a medium which contained radioactive phosphorus(32P) and some in radioactive sulphur(35S) medium. Viruses grown under radioactive (32P) contained radioactive DNA and Viruses grown under radioactive (35S) contained radioactive protein. When infected in E.coli separately, bacterial cells were gently agitated in blender to remove viralcoats from the bacteria. Culture was also centrifuged. Radioactive 32P was found to be associated with the bacterial cell whereas Radioactive 35S was found in the surrounding medium. Hence, the process resulted in viral DNA. 

QUESTION: 8

Which of the following is a structural subunit of DNA?

Solution:

Nucleotides are organic molecules that serve as the monomers, or subunits, of nucleic acids like DNA and RNA. The building blocks of nucleic acids, nucleotides are composed of a nitrogenous base, a five-carbon sugar and at least one phosphate group.

QUESTION: 9

Which of the following are the functions of RNA?

Solution:

mRNA carries genetic information from DNA to ribosomes for synthesising polypeptide chains. tRNA carries amino acids to mRNA for translation. rRNA is a vital component of ribosomes.

QUESTION: 10

While analysing the DNA of an organism, a total number of 5386 nucleotides were found out of which the proportion of different bases were Adenine = 29%, Guanine = 17%, Cytosine = 32% and Thymine = 17%. Considering the Chargaff’s rule, it can be concluded that

Solution:

 In the DNA of an organism a total number of 5386 nucleotides were found out of which the proportion of different bases were: Adenine = 29%, Guanine = 17%, Cytosine = 32%, Thymine = 17%. Considering the Chargaff’s rule it can be concluded that it is a single stranded DNA.

QUESTION: 11

Nitrogenous bases present in DNA:

Solution:
QUESTION: 12

Beadle and Tatum showed that each kind of mutant bread mould they studied lacked a specific enzyme. Their experiments demonstrated that

Solution:

Beadle and Tatum proposed their one gene one enzyme hypothesis on the basis of biochemical genetics in Neurospora crassa. Beadle and Tatum showed that each kind of mutant bread mould lacke a specific enzyme. Their experiments demonstrated that genes carry information for making proteins.

QUESTION: 13

A typical nucleosome contains

Solution:

Nucleosomes can be said when the DNA is wrapped around the histone protein, so this structure is called nucleosome and it has 200 base pairs of the DNA helix.

QUESTION: 14

Which one of the following is a base analogue 

Solution:

5-bromo uracil (Bu) is base analogue of thymine. Transitions are caused by base analogues.

QUESTION: 15

In the DNA molecule,​

Solution:
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