Genetic Code

Q. In the genetic code dictionary how many codons are used to code for all the 20 essential amino acids?
(A) 20
(B) 64
(C) 61
(D) 60

Q.

Which one of the following is the starter codon?

1. UAA

2. UGA

3. UAG

4. AUG

Q.

Which one of the following pairs of codons is correctly matched with their function or the signal for the particular amino acid?

1. AUG, ACG – start/methionine

2. UAG, UGA – stop

3. GUU, GCU – alanine

4. UUA, UCA – leucine

Q. Initiation codons for protein synthesis are

1. UUU and GGG
2. AAU and UAA
3. AUG and GUA
4. GUG and AUG.

Q. Arrange the following amino acids on the basis of an increasing number of triplet codes.
(1) Leucine
(2) Tryptophan
(3) Valine
(4) Phenylalanine

1. 1—2—3—4
2. 2—4—3—1
3. 2—3—4—1
4. 3—1—2—4

Q. The DNA segment 3' TACATGGCTCCG 5', transcribes one mRNA. Four tRNAs with anticodons listed below are required for translation. What is the order of tRNAs?
(a) AUG
(b) UAC
(c) CCG
(d) GCU

1. a, b, d, c
2. b, a, d, c
3. a, b, c, d
4. b, a, c, d

Q. What is a triplet codon?

1. Fixed
2. Degenerate
3. Ambiguous
4. Non-wobbly

Q. Work of Beadle and Tatum on Neurospora crassa proved that

1. replication of DNA is semi-conservative
2. viruses have genetic material
3. every gene is responsible for specific enzyme
4. plant cells are totipotent.

Q. Termination codons for protein synthesis are

1. AUU, AUG and GUU
2. UGA, UAA and UAG
3. UAU, UAG and UUA
4. AAA, UUU and UGA

Q. Which triplet codon does not have a tRNA associated with it?

1. UAA
2. UUA
3. UUU
4. AUU

Q. The idea that a combination of three bases should code for each amino acid was proposed by

1. Francis Crick
2. James Watson
3. George Gamow
4. Alec Jeffreys

Q. Match the following.

(I) AUG	(A) Stop codon
(II) AGU	(B) Serine
(III) UGA	(C) Initiation codon

1. (I)-(A), (II)-(B), (III)-(C)
2. (I)-(C), (II)-(A), (III)-(B)
3. (I)-(C), (II)-(B), (III)-(A)
4. (I)-(B), (II)-(A), (III)-(C)

Q. Which codon is not an indicator of completion of protein synthesis?

1. UAA
2. UGA
3. AUG
4. UAG

Q. Given below is sequence of the processed mRNA ready for translation
5' AUG CUA UAC UAA CUG CCA UGC UAG 3'
How many amino acids will present in polypeptide chain corresponding to this mRNA?

1. 7
2. 8
3. 6
4. 3

Q. Who among the following won the Nobel Prize for their work on Genetic Code?

1. Holley, Nirenberg and Khorana
2. Nirenberg and Matthaei
3. Nirenberg and Holley
4. Holley and Ochoa

Q. The DNA segment 3' TACATGGCTCCG 5', transcribes an mRNA. Four tRNAs with anticodons listed below are required for translation.
i) AUG
ii) UAC
iii) CCG
iv) GCU
Choose the correct sequence in which tRNAs would bind to the mRNA

1. II, I, IV, III
2. II, I, III, IV
3. I, II, III, IV
4. I, II, IV, III

Q. The DNA segment 3' TACATGGCTCCG 5', transcribes an mRNA. Four tRNAs with anticodons listed below are required for translation.
i) AUG
ii) UAC
iii) CCG
iv) GCU
Choose the correct sequence in which tRNAs would bind to the mRNA

1. I, II, IV, III
2. II, I, IV, III
3. I, II, III, IV
4. II, I, III, IV

Q. The DNA strand acting as a template for RNA has the base sequence AGCTTCGA. What will be the corresponding base sequence in mRNA?

1. TCGAAGCT
2. UGCUAGCT
3. TCGAUCGU
4. UCGAAGCU

Q. The most unstable RNA is

1. Messenger RNA
2. Soluble RNA
3. Ribosomal RNA
4. Heterogeneous nuclear RNA

Q. Assertion :There are 5487 codons in mature mRNA ready for translation. Reason: It can be translated into polypeptide with 1826 amino acids.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
3. Assertion is correct but Reason is incorrect.
4. Both Assertion and Reason are incorrect.

Q. Assertion :Ribozymes are RNA molecules which catalyse the synthesis of certain specific RNAs and removal of introns from mRNA. Reason: Ribozymes are proteinaceous enzymes.

1. Both statements 1 and 2 are correct.
2. Statement 1 is correct but statement 2 is incorrect.
3. Statement 1 is incorrect but statement 2 is correct.
4. Both statements 1 and 2 are incorrect.

Q. Whose experiments cracked DNA and discovered triplet nature of genetic code?

1. Beadle and Tatum
2. Hershey and Chase
3. Morgan and Sturtevant
4. Nirenberg and Matthaei

Q. Beadle and Tatum did classical experiments on Neurospora crassa to prove

1. One gene produces one enzyme.
2. One enzyme can correct one gene.
3. Many genes produce one enzyme.
4. None of the above.

Q. In an amino acid sequence of a primary structure of protein, the consequent amino acids are linked by

1. Alpha and beta bond
2. S.S. bond
3. Peptide bond
4. Nucleotides

Q. Studies by Beadle and Tatum that produced the one-gene one-enzyme hypothesis were conducted using the:

1. bread mold Neurospora crassa
2. bacterium Streptococcus pneumoniae
3. bacterium Escherichia coli
4. mushroom Agaricus bisporus

Q. Broad spectrum antibotics like streptomycin bind to smaller subunits of ribosomes of prokaryotes thereby

1. Inhibiting protein synthesis
2. Misleading of genetic code
3. Blocking action of peptidyl transferase
4. Causing point mutation

Q. Sequence of nitrogen bases in nontemplate strand of DNA was found to be CAT GTT TAT CGC. What would be sequence of nitrogen basis in mRNA synthesised over the corresponding region of template strand _______________.

1. CAU GUU UAU CGG
2. CAA GAA TAU GCC
3. GUA CAA AUA GCC
4. GTA CAA ATA GCC

Q. The codon sequence on coding strand of transcription unit is ATG GTG AGC TAC GCG. What will be the codon sequence on mRNA formed on template strand?

1. ATG GTG AGC TAC GCG
2. GCG TAC AGC GTG ATG
3. AUG GUG AGC UAC GCG
4. TAC CAC TGC ATG CGC

Q. Who coined the term linkage?

Q. what is meant by transcriptionally active and trans. inactive?