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DNA and Genetic Code

Description: its about genetic code.
Number of Questions: 15
Created by:
Tags: DNA genetic code Gene Expression and Regulation Regulation of Gene Expression Transcription Process of Transcription Translation Process of Translation DNA Replication Replication of DNA Protein Synthesis
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When an amino acid is represented by more than one codon, it is called __________.

  1. deaminate

  2. degenerate

  3. universal

  4. commaless

  5. non-overlapping

Show answer
Correct Option: B
Explanation:

The genetic code is degenerate in that most amino acids are encoded by more than one codon.

Which of the following codons codes for the same information as UGA?

  1. UAA

  2. AAU

  3. UUU

  4. UCG

  5. UGG

Show answer
Correct Option: A
Explanation:

UAA, UGA, and UAG are the stop codons. They do not code for any amino acid.

Degeneration of genetic code is attributed to __________.

  1. first member of the codon

  2. second member of the codon

  3. third member of the codon

  4. entire codon

  5. the code is non-degenerate

Show answer
Correct Option: C
Explanation:

The third base is called the wobble base. This base lacks specificity. For  e.g. inosine can pair up with more than one base at the same position resulting producing more than one codon for a single amino acid.

UGA, UAG and UAA are called as termination codons because __________.

  1. they terminate anticodons

  2. they are present at the beginning of mRNA

  3. they indicate initiation of translation

  4. they do not specify any amino acid

  5. they terminate mRNA

Show answer
Correct Option: D
Explanation:

It is true that nonsense codons do not code for any amino acid.

Which of the following has function similar to UGA and UAA?

  1. AUG

  2. UAG

  3. GUG

  4. UUU

  5. AGG

Show answer
Correct Option: B
Explanation:

UAA, UGA and UAG are the nonsense codons.

Exons help in the synthesis of __________.

  1. proteins

  2. fatty acids

  3. fats

  4. carbohydrates

  5. glycogen

Show answer
Correct Option: A
Explanation:

An exon is any nucleotide sequence encoded by a gene that remains present within the final mature RNA product of that gene after introns have been removed. It helps in the synthesis of proteins.

Which statement is false about genetic code?

  1. Genetic code is ambiguous.

  2. Genetic code is non-overlapping.

  3. Genetic code is degenerate.

  4. Genetic code is universal.

  5. Genetic code has start/stop signals.

Show answer
Correct Option: A
Explanation:

Genetic code is non-ambiguous, i.e. each codon specifies one amino acid only.

Sigma factor is associated with _________.

  1. RNA polymerase

  2. RNA ligase

  3. DNA polymerase

  4. DNA ligase

  5. DNA methylase

Show answer
Correct Option: A
Explanation:

A sigma factor (σ factor) is a protein needed only for initiation of RNA synthesis. It is associated with RNA polymerase enzyme.

What is the meaning of triplet codon?

  1. Presence of only three bases in r RNA

  2. A sequence of three bases in m-RNA

  3. A sequence of three bases in t-RNA

  4. A sequence of three bases in DNA.

  5. A sequence of three bases present in m, t or r RNA.

Show answer
Correct Option: B
Explanation:

A codon consists of the sequence of three nucleotides present in m RNA.

What does the degeneracy of genetic code refer to?

  1. One codon has many meanings.

  2. Many codons have the same meaning.

  3. Only two codons share many amino acids.

  4. Third base is not stable.

  5. During translation the genetic code is read one after the other in a sequence.

Show answer
Correct Option: B
Explanation:

A code in which several code words have the same meaning is called as degeneracy of genetic code.

Nonsense codons are called so because they _________.

  1. code for non-essential amino acids

  2. code for initiator amino acid, which is removed later

  3. are never present in the RNA

  4. do not code for any amino acid

  5. code for some special amino acids

Show answer
Correct Option: D
Explanation:

It is true as these are used as stop codons and these terminate the growing amino acid chain wherever they are present.

Out of the total 64 codons, 61 codes for 20 amino acids this suggests ___________.

  1. degeneracy of codons

  2. overlapping of codons

  3. redundancy of codons

  4. ambiguous nature of codons

  5. polarity of genetic code

Show answer
Correct Option: A
Explanation:

Only 20 amino acids are involved in protein synthesis, while there are 64 possibilities or types of codons. Hence, more than one codon can code for an amino acid. This is called as degeneracy of genetic code.

Which pair is correctly matched?

  1. UGG-start codon

  2. UUU-stop codon

  3. AGU-leucine

  4. UUC-isoleucine

  5. UAC-tyrosine

Show answer
Correct Option: E
Explanation:

UAC codes for tyrosine.

Tay sachs disease is an example of which kind of mutation?

  1. Frame shift mutation

  2. Deletion mutation

  3. Addition mutation

  4. Missense mutation

  5. Nonsense mutation

Show answer
Correct Option: A
Explanation:

Mutations that disrupt the reading frame sequence by insertion or deletion of a non-multiple of 3 nucleotide bases are known as frameshift mutation.

Which statement is not true regarding translation machinery?

  1. Anticodon consists of three nucleotides.

  2. Anticodon may pair with more than one codon.

  3. It is the basic unit of genetic code.

  4. tRNA is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length.

  5. The covalent attachment to the tRNA 3’ end is catalyzed by enzymes called aminoacyl tRNA synthetases.

Show answer
Correct Option: C
Explanation:

This statement is not true as codon, which is a sequence of three nucleotides on m-RNA, is the basic unit of genetic code.

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