This set of Protein Engineering Multiple Choice Questions & Answers (MCQs) focuses on “The Genetic Code”.
1. Which of the following is the correct sequence of central dogma?
a) Protein → RNA → DNA
b) RNA → protein → DNA
c) DNA → protein → RNA
d) DNA → RNA → protein
View Answer
Explanation: Genetic information is encoded in almost every cell in the form of DNA. This information is then transcribed into an RNA intermediate. This RNA serves as a template for the synthesis of proteins. Hence, the correct sequence is DNA → RNA → protein.
2. Who proposed the central dogma?
a) Louis Pasteur
b) Gregor Mendel
c) Francis Collins
d) Francis Crick
View Answer
Explanation: Louis Pasteur proposed the phrase Central dogma. He also discovered the double helix of DNA structure. Central Dogma is how the DNA sequence is converted into a protein sequence with the help of an RNA intermediate.
3. What is the genetic code?
a) Code of enzymatic analysis of genes
b) Code of genome sequencing
c) The message stored in proteins for the synthesis of DNA
d) The message stored in DNA for the synthesis of proteins
View Answer
Explanation: The genetic code is the message stored in DNA for the synthesis of proteins. Proteins are the building blocks of life. To synthesize correct protein sequence DNA provides an important message.
4. What is a codon?
a) A single base necessary to specify a single amino acid
b) A group of two bases necessary to specify a single amino acid
c) A group of three bases necessary to specify a single amino acid
d) A group of several bases necessary to specify a single amino acid.
View Answer
Explanation: A codon is a group of several bases necessary to specify a single amino acid. The genetic code need not specifically be restricted to only two or three bases every time. In this way, the encoded genetic information in the DNA is decoded for protein synthesis.
5. If a codon contains four bases, then how many possible codons can be formed utilizing the four most commonly occurring bases?
a) 16
b) 64
c) 704
d) 256
View Answer
Explanation: The total number of possible codons is 256.
Formula: p=4n
Where p is the number of possible codons, n is the number of bases in a codon.
p=44
p=256.
6. The triplet code allows many amino acids to be specified by more than one codon. Such a code is said to be degenerate?
a) False
b) True
View Answer
Explanation: The above statement is true. When a triplet code allows many amino acids to be specified by more than one codon, the code is said to be degenerate. Hence, a single amino acid can be specified by two/three codons.
7. Which of the following gives the correct characteristics of the genetic code?
a) Duplet, overlapping, and degenerate
b) Duplet, non-overlapping, and degenerate
c) Triplet, overlapping, and degenerate
d) Triplet, non-overlapping, degenerate
View Answer
Explanation: The characteristics of genetic code are as follows: triplet, non-overlapping, degenerate. The genetic code mainly comprises of three bases, hence, it is called a triplet. The codons do not overlap with each other.
8. Which of the following mutation is known as frameshift mutation?
a) All mutations
b) Only the deletion of single nucleotide
c) Only addition of a single nucleotide
d) Both addition and deletion of single nucleotide
View Answer
Explanation: Both addition and deletion of single nucleotides are known as frameshift mutations. When there is an addition or deletion of a single nucleotide in the genome it disrupts the reading frame of genetic code.
9. The genetic code has no punctuation to indicate the reading frame; instead, the nucleotide sequence is read sequentially, triplet by triplet?
a) False
b) True
View Answer
Explanation: The nucleotides in the genetic code are arranged one after the other without any gap or break. Hence, the genetic code has no punctuation to indicate the reading frame, and the nucleotide sequence is read sequentially, triplet by triplet.
10. Which of the following is the start codon?
a) CUC
b) ACC/CCA
c) GUA
d) AUG/GUG
View Answer
Explanation: AUG/GUG in the genetic code appears at the start of the genetic sequence. It specifies for methionine amino acid. The first tRNA to bind the mRNA binds to this position. Hence, AUG/GUG is the start codon for nearly all organisms.
11. Which amino acid does AUG code for?
a) Cysteine
b) Valine
c) Glycine
d) Methionine
View Answer
Explanation: AUG is a start codon and is specifies for methionine. Thus, the first amino acid to be added to the sequence is methionine. Later, this amnio acid can be removed proteolytically.
12. Find the odd one out?
a) UAA
b) UAG
c) UGA
d) AUG
View Answer
Explanation: AUG is a start codon, while UAA, UAG, and UGA are stop codons. Stop codons occur at the sequence in the mRNA where the translation is to be stopped. Hence, AUG is the odd one out.
13. Which of the following codons are known as non-sense codons?
a) UGA only
b) UAG only
c) UAA only
d) UGA, UAG, and UAA
View Answer
Explanation: UGA, UAG, and UAA all stop codons. Since they do not code for any amino acid they are also called non-sense codons. They don’t even have a specific tRNA.
14. What are the codons that specify the same amino acid called?
a) Stop codons
b) Start codons
c) Acronyms
d) Synonyms
View Answer
Explanation: Codons that specify the same amino acid calledsynonyms. Codons are highly degenerate. E.g. Arg, Leu, and Ser are each specified by six different codons.
15. The “standard” genetic code is almost universal?
a) False
b) True
View Answer
Explanation: The above statement is true because one kind of organism can accurately translate the genes for quite a different organism. But, the genetic code of some mitochondria are not standard, but they are a variant of the standard.
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