Structure of DNA

Q.

If E. coli was allowed to grow for 80 minutes then what would be the proportions of light and hybrid densities in a DNA molecule?

Q.

Calculate the number of phosphodiester, and glycosidic bonds in 100 base pairs long double-stranded DNA.

Q.

Which property of DNA double helix led Watson and Crick to hypothesize semi- conservative mode of DNA replication? Explain.

Q. According to Watson and Crick model __ base pairs are present in each turn of helix.

1. 18
2. 12
3. 10
4. 11

Q.

1.7 m double helical DNA will have how many base pairs?

Q.

From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?

Q.

Regarding the assertion and reason, select the correct option.

Assertion [A]: A polynucleotide chain exhibits polarity.
Reason [R]: At one end of the polynucleotide chain, a phosphate group is found attached to the fifth (5’) carbon of the sugar ring (of the respective nucleotide), and at other end, a free 3’ -OH group is present.

1. Both A and R are true and R explains A

2. Both A and R are true, but R does not explain A

3. A is true and R is false

4. Both A and R are false

Q. If there are 120 adenine molecules in a DNA double helical structure showing 20 coils, what is the number of pyrimidine nucleotides forming three hydrogen bonds in it?

1. 80
2. 100
3. 120
4. 140

Q. In B-DNA, one full turn of the helical strand contains

1. 11 base pairs
2. 8 base pairs
3. 10 base pairs
4. 9 base pairs

Q. Watson and Crick proposed the model of DNA structure in

1. 1953
2. 1943
3. 1955
4. 1963

Q.

How far is each base pair from the next one in a double helix DNA?

1. 0.34nm

2. 0.34mm

3. 0.43nm

4. 0.43mm

Q.

How many different monomers are there in DNA?

Q.

What Is Terminal Redundancy In T4 DNA?

Q.

What does it mean when it is said that both DNA chains have antiparellel polarity?

Q. DNA fragments are :

1. Positively charged
2. Negatively charged
3. Neutral
4. Either positively or negatively charged depending on their size

Q.

From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?

Q.

What is Z-dna and B-dna?

Q. Pyrimidine base that has conferred additional stability to
DNA over RNA is

1. Guanine
2. Thymine
3. Adenine
4. Cytosine

Q. The nitrogenous bases of the two strands of DNA are joined by

1. Phosphodiester bond
2. Hydrogen bond
3. Glycosidic bond
4. Peptide bond

Q.

What Is the 3 Prime End of DNA?

Q. The scientists involved in discovery of DNA as chemical basis of heredity were

1. Griffith and Avery
2. Hershey and Chase
3. Avery, Mac Leod and Mc Carty
4. Watson and Crick

Q. The diameter of B-DNA was found to be 20Å by the study of

1. Erwin Chargaff's conclusions
2. Meselson and Stahl's experiment
3. Franklin and Wilkins' X-ray diffraction studies
4. Watson and Crick's three dimensional model

Q.

Semi-discontinuous mode of DNA replication was discovered by

1. Meselson and Stahl

2. Watson and Crick

3. Hershey and Chase

4. Okazaki and Okazaki

Q. (a) Explain the significance of 'palindromic nucleotide sequence' in the formation of recombinant DNA.

(b) Write the use of restriction endonuclease in the above process. [3]

Q. In a DNA segment having 4 coils, there are 20 base pairs, each linked by two hydrogen bonds. How many cytosine bases are found in that segment?

1. 0
2. 400
3. 20
4. Information is not enough to find the answer

Q. If Meselson and Stahl's experiment is continued for three generations in bacteria. The ratio of $15N/15N:15N/14N:14N/14N$ containing DNA in the third generation would be

1. $0:1:7$
2. $1:4:0$
3. $0:1:3$
4. $0:1:4$

Q.

The double helical model of DNA was first constructed by:

1. Levene and Chargaff

2. Hershey and Chase

3. Watson and Crick

4. Wilkins and Franklin

Q. Given below is a sample of portion of DNA strand giving the base sequence on the opposite strands. What is so special shown in it?
5'-GAATTC-3'
3'-CTTAAG-5'

1. Deletion mutation
2. Start codon at the 5' end
3. Palindromic sequence of base pairs
4. Replication completed

Q. Choose the incorrect statement w.r.t. nucleases.

1. Exonucleases and endonucleases are two kinds of nucleases
2. Exonucleases remove nucleotides from the ends of the DNA
3. Restriction endonucleases make cuts at random position within the DNA
4. Each restriction endonuclease functions by inspecting the length of a DNA sequence

Q.

Base pairs found in one turn of the DNA spiral are:

1. 12

2. 11

3. 10

4. 8