Molecular Basis of Inheritance Test

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Molecular Basis of Inheritance Test - 1

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Weekly Quiz Competition

Question 1
4 / -1

Which of the following pairs is incorrectly matched?

A
Purines-Adenine and Guanine

B
Pyrimidines-Cytosine and Uracil

C
Nucleosides-Adenosine and Thymidine

D
DNA-Basic biomolecule

Solution

DNA (deoxyribonucleic acid) is an acidic biomolecule.
Question 2
4 / -1

Choose the correct answer from the alternatives given :
Given figure represents the DNA double helix model is proposed by Watson and Crick (1953). Select the option that shows correct measurements of A, B and C.

A
A-3.4nm, B-0.34nm, C-2nm

B
A-34 rim, B-3.4 nm, C-20 nm

C
A−3.4Å, B−0.34Å, C−20Å

D
A−34Å, B−3.4Å, C−2Å

Solution

The DNA helix makes one complete spiral turn every 3.4 nm and has a diameter of 2nm. The distance between adjacent stacks is 0.34 nm.
Question 3
4 / -1

Refer the given figure of nucleosome and select the option that correctly identifies the parts A, B and C.

A
a

B
b

C
c

D
d

Solution

In eukaryotes, DNA organisation is complex. There is a set of positively changed, basic porteins called histones. Histones are rich in the basic amino acid residues lysine and arginine. There are five types of histone proteins-H₁,H₂A,H₂B,H₃and H₄. Four of them (H₂A,H₂B,H₃and H₄) produce histone octamer called nu body or core of nucleosome . The negatively charged DNA is wrapped around the positively charged histone octamer to form nucleosome. DNA connecting two adjacent nucleosomes is called linker DNA which bears H₁ histone proteins.
Question 4
4 / -1

If a double stranded DNA has 20% of cytosines, calculate the percent of adenine in the DNA.

A
20%

B
40%

C
30%

D
60%

Solution

In a DNA molecule, the number of cytosine molecules is equal to guanine molecules and the number of adenine molecules are equal to Thymine molecules. Thus, If a double stranded DNA has 20% of cytosine, it has 20% of guanine. Thus, cytosine plus guanine make 40% of the total bases. The remaining 60% includes both adenine and thymine which are in equal amounts. Therefore, the percent of adenine is 30%.
Question 5
4 / -1

Refer to the given sequence of steps and select the correct option.

A
(i) Replication, (ii) Transcription, (iii) - Translation

B
(i) Replication, (ii) Processing, (iii) - Translation

C
(i) Transcription, (ii) Splicing, (iii) - Translation

D
(i) Transcription, (ii) Replication, (iii) - Translation

Solution

DNA contains genetic information which is transcribed via mRNA. mRNA is not made directly in eukaryotic cell. It is transcribed in the nucleus as hnRNA which contains introns and exons. The introns are removed by RNA splicing leaving behind exons which contain the information. The exonic regions of RNA are joined together to produce a single chain RNA required for functioning as translational template. This information is then translated into polypeptide chains.
Question 6
4 / -1

If the sequence of bases in one strand of DNA is ATGCATGCA, what would be the sequence of bases on complementary strands?

A
ATGCATGCA

B
AUGCAUGCA

C
TACGTACGT

D
UACGUACGU

Solution

Adenine always pairs with thymine and cytosine always pairs with guanine. Thus, sequence of bases on complementary strand would be TACGTACGT.
Question 7
4 / -1

Read the following statements and select the Correct option.
(i) Loosely packed and lightly stained region of chromatin are called as heterochrormatin.
(ii) Densely packed and dark stained region of chromatin are called as euchromatin.
(iii) A typical nucleosome contains 200 bp of DNA helix.

A
Statements (i) and (ii) are true, but statement (iii) is false.

B
Statements (i) and (ii) are false, but statement (iii) is true.

C
Statements (ii) and (iii) are true, but statement (i) is false.

D
All the statements are true.

Solution

A typical nudeosome contains 200bp of DNA helix. Nudeosomes constitute the repeating unit of a structure in nucleus called chromatin. Chromatin is held over a scaffold of non-histone chromosomal (or NHC) proteins. At some places chromatin is densely packed to form darkly stainined heterochromatin. At other places chromatin is loosely packed. It is called euchromatin. It is transcriptionally active chromatin whereas heterochromatin is transcriptionally inactive and late replicating or heteropycnotic.
Question 8
4 / -1

Chemically, RNA is (i) reactive and (ii) stable as compared to DNA.

A
(i) equally, (ii) equally

B
(i) less, (ii) more

C
(i) more, (ii) less

D
(i) more, (ii) equally

Solution

2OH group present in ribose sugar of every nucleaotide of RNA is a reactive group. Uracil present in RNA is less stable as compared to thymine (= methyl uracil) of DNA. Being unstable, RNA mutates at a much faster rate and there is no repairing system.Consequently, viruses having RNA genome and having shorter life span mutate and evolve faster.
Question 9
4 / -1

In a DNA strand, the nucleotides are linked together by

A
glycosidic bonds

B
phosphodiester bonds

C
peptide bonds

D
hydrogen bonds

Solution

In a DNA strand, the nucleotides are linked together by 3'-5' phosphodiester linkage (bonds ) to form a dinucleotide. More nucleotides can be joined in such a manner to from a polynucleotide chain.
Question 10
4 / -1

Which of the following shows the correct positions of the phosphate (P), sugar (S) and base (B) molecules in the given line diagrams representing the structure of DNA

A

B

C

D

Solution

DNA helix is made up of two polynucleotide chains, where the backbone is constituted by sugar-phosphate and the bases project inside.
Question 11
4 / -1

What does A and B represent in the given representation in the Diagram?

A
A - Ribonucleoside, B - Deoxyribonucleoside

B
A - Ribonucleotide, B - Deoxyribonucleotide

C
A- Nucleoside, B - Nucleotide

D
A - Nucleotide, B - Nucleoside

Solution

Sugar + Nitrogenous base → Nucleoside Sugar + Nitrogenous base + Phosphate → Nucleotide.
Question 12
4 / -1

In one polynucleotide strand of a DNA molecule, the ratio of A+T/G+C is 0.3. what is the A +G/T +C ratio of the entire DNA molecule?

A
0.3

B
0.6

C
1.2

D
1

Solution

According to Chargaff's rules (1950), purine and pyrimidine base pairs are present in equal amounts in a DNA molecule.
i.e., [A+B]=[T+C]
Question 13
4 / -1

The structure in chromatin seen as 'beads-on' string' when viewed under electron microscope are called

A
nucleotides

B
nuclesides

C
histone octamer

D
nucleosomes

Solution

Nucleosomes constitute the repeating unit of a structure in nucleus called chromatin, thread-like stained (coloured) bodies seen in nucleus. The nucleosomes in chromatin are seen as 'beads-on-string' structure when viewed under electron microscope.
Question 14
4 / -1

Choose the correct answer from the alternatives given :
If the DNA of a virus is labelled with 32P and the protein of the virus is labelled with 355, after transduction which molecule(s) would be present inside the bacterial cells?

A
32P only

B
35S only

C
Both (a) and (b)

D
None of these
Solution
Bacteria which were infected with viruses that had radioactive DNA (incorporated with ³²P) were radioactive, indicating that DNA was the material that passed from the virus to the bacteria.
Bacteria that were infected with viruses that had radioactive proteins (incorporated with ³⁵S) were not radioactive. DNA is therefore, the genetic material that is passesd from virus to bacteria.
Question 15
4 / -1

Choose the correct answer from the alternatives given:
The year 2003 was celebrated as the 50th anniversary of discovery of

A
Transposons by Barbara Mc Clintock

B
Structure of DNA by Watson and Crick

C
Mendels laws of inheritance

D
Bio technology by Kary Mullis

Solution

Watson and Crick (1953) worked out the first correct double helix model from the X-ray photographs of Wilkins and Franklin. They were awarded Nobel Prize for the same in 1962.