Molecular Basis of Inheritance Test

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Molecular Basis of Inheritance Test - 84

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Weekly Quiz Competition

Question 1
1 / -0

The double helical model of the DNA was proposed by Watson and Crick based on that what data produced by Wilkins and Franklin?

A
Hybridization

B
DNA sequencing

C
Southern blotting

D
X-ray diffraction

E
Both A and D

Solution

Watson and Crick's proposed model of DNA was based on the data given from various experiments and important X-ray crystallography work by Rosalind Franklin and Maurice Wilkins
Question 2
1 / -0

Which of the following is not relevant to the structure of double helical DNA?

A
The helix makes one complete spiral turn every 34A$$^o$$.

B
The diameter of the helix is 20A$$^o$$.

C
The distance between adjacent nucleotide is 3.4A$$^o$$.

D
Each strand of helix has a backbone made up of alternating ribose sugar and phosphate.

E
The two adjacent sugar molecules joined with phosphate by phosphodiester bond.

Solution

The two DNA strands are known as polynucleotides since they are composed of simpler units called nucleotides. Each nucleotide is composed of a nitrogen - containing nucleobase - either guanine, adenine, thymine or cytosine - as well as a monosaccharide sugar called deoxyribose and a phosphate group.
Question 3
1 / -0

Which one of the following group of codons is called as degenerate codons?

A
UAA, UAG and UGA

B
GUA, GUG, GCA and GCG

C
UUC, UUG, CCU, CAA and CUG

D
UUA and UUG, CUU, CUC and CUG

E
AAC, AAG, GAC and CGG

Solution

Degenerate codons may differ in their third positions; e.g., both GAA and GAG code for the amino acid glutamic acid. A codon is said to be four-fold degenerate if any nucleotide at its third position specifies the same amino acid; it is said to be two-fold degenerate if only two of four possible nucleotides at its third position specify the same amino acid.
Question 4
1 / -0

Which one of the following is correct?

A
Introns are present in mRNA and exons are present in tRNA.

B
Codons are present in mRNA and anticodons in tRNA.

C
Every intron is a set of three terminator codons.

D
Exons are present in eukaryotes while introns are present in prokaryotes.

Solution

A. Introns are the non coding regions and exons are the coding regions in DNA. DNA undergoes transcription to form RNA which then undergoes splicing to remove the non coding regions i.e. introns.
B. Codons are the set of genes that are translated into proteins. These are present in mRNA. Anticodon is the sequence complementary to codons and is present in tRNA. The anticodon arm of tRNA has sequence of base pairs that are complementary to codons of mRNA.
C. Introns are the non coding regions. Each intron consists of three base pairs. These do not code for any protein. Terminator codons are three in number which are UAA, UAG and UGA. These are also known as stop codons and direct the signal for termination of translation.
D. Exons are present in both eukaryotes and prokaryotes whereas introns are present only in eukaryotes.
Hence, statement B is correct.
So, the correct answer is 'Codons are present in mRNA and anticodons in tRNA'.
Question 5
1 / -0

Which enzyme catalyzes the separation of DNA strands during DNA replication?

A
DNA polymerase

B
Helicase

C
Ligase

D
Topoisomerase

Solution

A. DNA polymerase adds deoxyribonucleotides to the 3'-OH end of the growing polynucleotide chain.
B. Helicase helps in unwinding the two strands of DNA double helix during replication.
C. Ligase joins the DNA strand by catalyzing the formation of a phosphodiester bond between the adjacent bases.
D. Topoisomerase helps in relieving the tension created during the unwinding of DNA.
Hence, the enzyme that catalyzes the separation of DNA strands during DNA replication is Helicase.
So, the correct answer is 'Helicase'.
Question 6
1 / -0

Identify the correct and incorrect statements.
A. The four nucleotide bases are not necessarily present in DNA in exact equal proportions.
B. The total amount of purines are equal to the total amount of pyrimidines.
C. DNA ligase enzyme act to hydrolyse or breakdown a polynucleotide chain into its component nucleotides.
D. Nuclease enzymes are capable of restoring an intact DNA duplex.

A
B is correct but A, C and D are wrong.

B
A and B are wrong but C and D are correct.

C
A, B and C are correct but D is wrong.

D
A and B are correct but C and D are wrong.

E
B, C and D are correct but A is wrong.
Solution
- According to Leven's tetranucleotide theory, the four nucleotidess present in the DNA are in equal molar proportion and are not necessarily present in exactly equal proportion.
- According to Chargaff's rules, the DNA from any cell of all organisms pyrimidine and purine should be in the ratio of 1:1 (base Pair Rule). He further concluded that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine.
- DNA ligase facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.
- Nuclease is an enzyme that cleaves nucleic acids.
Thus, the correct answer is option D.
Question 7
1 / -0

The base sequence for a nucleic acid segment is given CAG, AGG, CGA, CCA. From this, it can definitely be concluded that it is a segment of which strand?

A
DNA strand

B
mRNA strand

C
tRNA strand

D
Data not sufficient

Solution

Data is not sufficient. Because the distinction is done on the basis of presence of thymine in DNA and uracil in RNA, which are unique nitrogenous bases for those nucleic acids.
Question 8
1 / -0

In a given DNA segment, the number of nucleotides of guanine is 75 and those of thymine is 75. What will be the total number of nucleotides in the segment?

A
75

B
750

C
225

D
300
Solution
Chargaff's law = A + G = T + C
Also, the number of adenine is equal to thymine while the number of guanine is equal to cytosine.
From Chargaff's law mentioned above: A, T, G and C each has 75 nucleotides.
That is, 75 + 75 + 75 +75 = 300.
Question 9
1 / -0

In prokaryotes, the process of replication is catalysed by the following enzymes. Identify which of the enzymes is best coordinated with the role?

A
Helicase $$\rightarrow$$ Joins the ends of DNA segments

B
DNA polymerase I $$\rightarrow$$ Synthesis of DNA

C
DNA polymerase II $$\rightarrow$$ Erases primer and fills gaps

D
Primase $$\rightarrow$$ Synthesis RNA primers

Solution

DNA primase is an enzyme involved in the replication of DNA. DNA primase is a type of RNA polymerase which synthesizes RNA primer. This RNA primer is then extended by DNA polymerase to replicate ssDNA. Primase is an important enzyme of primosome complex.
Thus, the correct answer is option D.
Question 10
1 / -0

How many effective codons are there for the synthesis of twenty amino acids?

A
64

B
32

C
60

D
61
Solution
Correct option (D)

Explanation of the correct option :(D)
- George Gamow in 1954, pointed out the possibility of a three-letter code i.e. triplet codon.
- This will give 4 x 4 x 4 = 64 codons which are more than enough to code for twenty amino acids.
- Out of these 64 codons, 3 codons are stop codons.
- Hence, 61 effective codons are there for the synthesis of twenty amino acids.

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Molecular Basis of Inheritance Test - 84

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Molecular Basis of Inheritance Test - 84

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SHARING IS CARING

Question 1

Hybridization

DNA sequencing

Southern blotting

X-ray diffraction

Both A and D

Solution

Question 2

The helix makes one complete spiral turn every 34A$$^o$$.

The diameter of the helix is 20A$$^o$$.

The distance between adjacent nucleotide is 3.4A$$^o$$.

Each strand of helix has a backbone made up of alternating ribose sugar and phosphate.

The two adjacent sugar molecules joined with phosphate by phosphodiester bond.

Solution

Question 3

UAA, UAG and UGA

GUA, GUG, GCA and GCG

UUC, UUG, CCU, CAA and CUG

UUA and UUG, CUU, CUC and CUG

AAC, AAG, GAC and CGG

Solution

Question 4

Introns are present in mRNA and exons are present in tRNA.

Codons are present in mRNA and anticodons in tRNA.

Every intron is a set of three terminator codons.

Exons are present in eukaryotes while introns are present in prokaryotes.

Solution

Question 5

DNA polymerase

Helicase

Ligase

Topoisomerase

Solution

Question 6

B is correct but A, C and D are wrong.

A and B are wrong but C and D are correct.

A, B and C are correct but D is wrong.

A and B are correct but C and D are wrong.

B, C and D are correct but A is wrong.

Solution

Question 7

DNA strand

mRNA strand

tRNA strand

Data not sufficient

Solution

Question 8

75

750

225

300

Solution

Question 9

Helicase $$\rightarrow$$ Joins the ends of DNA segments

DNA polymerase I $$\rightarrow$$ Synthesis of DNA

DNA polymerase II $$\rightarrow$$ Erases primer and fills gaps

Primase $$\rightarrow$$ Synthesis RNA primers

Solution

Question 10

64

32

60

61

Solution

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