CBSE Questions for Class 12 Medical Biology Molecular Basis Of Inheritance Quiz 3 - MCQExams.com

• Transcription in genetics refers to the process of recording or copying a DNA's message onto a related RNA in its language. 
• The transcription unit is made up of a promoter, structural gene, and a terminator. 
• The promoter initiates and controls the process, while the terminator indicates when and where to stop transcribing. 
• Each gene has its own promoter and in eukaryotes, the promoter is always the same and is known as the TATA box as the sequence of bases is TATAAA.
• The transcription unit extends from the TATA box to the stop codon or the terminator.
  

• The human genome project was a mega-project whose aim was to sequence the human genome with the help of bioinformatics. 
• With the help of this project, we estimated that the human genome has 3.1 billion nitrogenous bases in its DNA. 
• The nitrogenous bases are adenine, thymine, guanine, and cytosine. 

• DNA fingerprinting is a method used to identify an individual from a sample of DNA by looking at unique patterns in their DNA. The technique was developed in 1984 by the British geneticist Alec Jeffreys.
• Variable Number of Tandem Repeat (VNTR) polymorphism is the basis of DNA fingerprinting which are short nucleotide repeats. The location and repetition in VNTR are so unique that no two individuals are alike.

• The sequence of amino acids in proteins depends on the sequence of nucleotides in DNA.
• The DNA produces mRNA molecules through the process of transcription. The mRNA is transported to the cytoplasm where it is translated into protein.
• A sequence of three nucleotides in mRNA specifies a particular amino acid in a protein chain.
  Hence, the genetic codon is a triplet.
  So the correct answer is A.

• The three nucleotides together on mRNA is known as codon which codes for particular amino acids. 
• The RNA has the sequence of UGUGUGUGUGUG that codes for tetrapeptides which contain only cysteine and valine. 
• Thus, the codons UGU and GUG codes for cysteine and valine respectively. 

• The bacterial genome contains double-stranded circular DNA. It also contains short circular DNA called a plasmid. 
• It is a self-replicating unit that mainly helps in transformation.
  

$$\textbf{Correct option: (A)}$$

$$\textbf{Solution:}$$

$$\textbf{Option (A):}$$

Correct Option: A

Explanation:

• Translation is initiated with a chain initiation codon and terminates with a stop codon.
• The initiation codon is the first codon of a messenger RNA translated by a ribosome.
• AUG codes for methionine in eukaryotes.
•  AUG is an initiation codon as translation begins from this codon. 

• The genetic code is the set of rules by which information encoded within genetic material, i.e., the DNA or mRNA sequences, is translated into proteins by living cells. 
• The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries. Hence, it is universal.
• There is no ambiguity in the genetic code. A given codon always codes for a particular amino acid wherever it is present.
  
• The coding units or codons for amino acids comprise three-letter words, 4 x 4 x 4 = 64 codons to specify 20 proteinous amino acids.