Molecular Basis of Inheritance Test

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Molecular Basis of Inheritance Test - 98

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Question 1
1 / -0

The relative percentages of nitrogenous bases of the genetic material isolated from various species (P, Q, R, S and T) are listed in the following table.
Species Adenine Guanine Thymine Cytosine Uracil
P $$21$$ $$29$$ $$21$$ $$29$$ $$0$$
Q $$29$$ $$21$$ $$29$$ $$21$$ $$0$$
R $$21$$ $$21$$ $$29$$ $$29$$ $$0$$
S $$21$$ $$29$$ $$0$$ $$29$$ $$21$$
T $$21$$ $$29$$ $$0$$ $$21$$ $$29$$

Choose the correct statement from the following.

A
Species P, Q and R contain single-stranded DNA; S and T cannot contain double-stranded RNA

B
Species P, Q and R contain double-stranded RNA; species S and T contain single-stranded RNA

C
Species P, Q and R cannot contain single-stranded DNA; species S contains single-stranded RNA; species T contains double-stranded RNA

D
Species P and Q contain double-stranded DNA; species R contains single-stranded DNA; species S contains double-stranded RNA; species T contains single-stranded RNA

Solution

DNA has base pairs adenine, thymine, guanine and cytosine. RNA has base pairs adenine, guanine, cytosine and uracil. In a double stranded DNA, number of adenine will always be equal to number of thymine and number of cytosine will always be equal to number of guanine as per Chargaff's rule. In species P, number of adenine are equal to number of thymine. Also, it has same number of guanine and cytosine. It does not have uracil in its genome. Hence, species P is double-stranded DNA. Similarly, species Q is double-stranded DNA. Species S has uracil instead of thymine in equal number as adenine. Also, number of guanine are equal to cytosine. Hence, species S is double-stranded RNA. T has uracil in its genome. Also, number of adenine are not equal to uracil and number of guanine are not equal to cytosine. Hence, species T is single-stranded RNA.
Thus, the correct answer is option D.
Question 2
1 / -0

The DNA model proposed by Watson and Crick

A
combined many of the findings of other researches also studying DNA such as Rosalind Franklin and Chargaff.

B
showed the double helix nature of the molecule

C
presented a molecule with sugar-phosphate backbones on the outside and paired bases on the inside

D
all of the above

Solution

Watson and Crick proposed a famous model of DNA double helix. Most of their clues regarding DNA structure came from Rosalind Franklin. Franklin was an expert in powerful technique for determining the structure of molecules, known as X-ray crystallography. When the crystallized form of a molecule such as DNA is exposed to X-rays some of the rays are deflected by the atoms in the crystal, forming a diffraction pattern that gives clues about the molecule structure. Watson and Crick proposed their model and said that the DNA molecule consists of two helically twisted strands connected together by base pairs, which align themselves in such a manner just like the steps of the ladder. Each strand consists of alternating molecules of the deoxyribose sugar and phosphate groups. The linkage between sugar and phosphate molecule is called a phosphodiester bond.
So, the correct option is 'all of the above'.
Question 3
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Choose the correct answer from the alternatives given :
Watson and Crick (1953) proposed DNA double helix model and won the Nobel Prize; their model of DNA was based on
(i) X-ray diffraction studies of DNA done by Wilkins and Franklin
(ii) Chargaffs base equivalence rule
(iii) Griffiths transformation experiment
(iv) Meselson and Stahls experiment.

A
(i), (ii) and (iv)

B
(i) and (ii)

C
(iii) and (iv)

D
(i), (ii), (iii) and (iv)

Solution

In 1953, James Watson and Francis Crick based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin, proposed double helix model for the structure of DNA. One of the hallmarks of their proposition was base pairing between two strands of polynucleotide chains. However, this proportion was also based on the observation of Erwin Chargaff (1950) that for a double stranded DNA, the ratios between Adenine and Thymine and Guanine and Cytosine are constant and equals one.
So, the correct answer is '(i) and (ii)'.
Question 4
1 / -0

Choose the correct answer from the alternatives given :
Which of the following figures correctly represents the replication fork formed during DNA replication?

A

B

C

D

Solution

Synthesis of DNA by DNA polymerases occurs only in 5 → 3 direction. One strand called leading strand, is copied in the same direction as the unwinding helix. The other strand is known as lagging strand Replication of lagging strand is in a discontinuous way, and in the direction of growth of lagging stand is 3 → 5 though in short segments of DNA which are always in the 5 → 3 direction. These short segments are called Okazaki fragments joined together by the action of DNA ligase.
So, the correct option is 'D'.
Question 5
1 / -0

Choose the correct answer from the alternatives given :
Other than DNA polymerase, which are the enzymes involved in DNA synthesis?

A
Topoisomerase

B
Helicase

C
RNA primase

D
All of these

Solution

Process of DNA synthesis whereby a parent DNA molecule is faithfully copied, giving rise to two identical daughter molecules is called DNA replication. In DNA synthesis, DNA polymerase plays an important role having the capability to elongate an existing DNA strand but cannot initiate the synthesis. So, the synthesis is initiated with the help of RNA primer formed by RNA primase RNA primase synthesises the short RNA primer of about 10 nucleotides that is elongated by DNA polymerase to form an Okazaki fragment of DNA during DNA replication. Helicase unzips the two strands of DNA and topoisomerase reduces the coiling tension developed due to the unwinding of the two strands.
So the correct answer is 'All of these'.
Question 6
1 / -0

Choose the correct answer from the alternatives given :
Which of the following phenomena was experimentally proved by Meselson and Stahl?

A
Transformation

B
Transduction

C
Semi-conservative DNA replication

D
Central dogma

Solution

The Meselson and Stahl experiment was an experiment to prove that DNA replication was semi-conservative and it was first shown in Escherichia coli and subsequently in higher organisms, such as plants and human cells. Semi-conservative replication means that when the double-stranded DNA helix was replicated, each of the two double-stranded DNA helices consisted of one strand coming from the parental helix and one is newly synthesized.
So, the correct answer is 'Semi-conservative DNA replication'
Question 7
1 / -0

If the sequence of bases in DNA is GCTTAGGCAA then the sequence of bases in its transcript will be

A
GCTTAGGCM

B
CGAATCCGTT

C
CGAAUCCGUU

D
AACGGAUUCG

Solution

mRNA strand is complementary to one of the DNA strands i.e., template strand. In RNA, uracil is present instead of thymine which is complementary to adenine. Cytosine and guanine are also complementary to each other. Hence, the sequence of bases in transcript would be CGAAUCCGUIJ.
Question 8
1 / -0

Choose the correct answer from the alternatives given :
The enzyme DNA dependent RNA polymerase catalyses the polymerisation reaction in ________ direction.

A
Only 5 $$\rightarrow$$ 3

B
Only 3 $$\rightarrow$$ 5

C
Both (a) and (b)

D
None of these

Solution

The two strands have opposite polarity and the DNA-dependent RNA polymerase also catalyze the polymerization in only one direction, that is, 5 → 3, the strand that has the polarity 3 → 5 acts as a template, and is also referred to as template strand. The other strand which has the polarity 5 → 3 and the sequence same as RNA (except thymine at the place of uracil) is displaced during transcription. This strand (which does not code for anything) is referred to as coding strand.
So, the correct answer is 'Only 5 → 3'.
Question 9
1 / -0

DNA replication takes place at ________ phase of the cell cycle

A
G$$_1$$

B
S

C
G$$_2$$

D
M

Solution

In eukaryotes, the replication of DNA takes place at S-phase of the cell cycle. The replication of DNA and cell division cycle should be coordinated. A failure in cell division after DNA replication results into chromosomal anomaly.
Question 10
1 / -0

Choose the correct answer from the alternatives given :
Read the following statements.
(i) One codon codes for only one amino acid.
(ii) Some amino acids are coded by more than one codon.
(iii) The, sequence of triplet nitrogenous bases in DNA or mRNA corresponds to the amino acid sequence in the polypeptide chain.
Give suitable terms for the characteristics of genetic code as per the above statements.

A
Degeneracy - (i), Colinearity - (ii), Unambiguous - (iii)

B
Degeneracy - (iii) , Colinearity - (ii) , Unambiguous - (i)

C
Degeneracy - (ii) , Colinearity - (iii) , Unambiguous - (i)

D
Degeneracy - (i) , Colinearity (ii) , Unambiguous - (iii)

Solution

As there are 64 combination of the base pairs A,G,U and C possible that are required to code for the 20 major amino acids more than one code can give rise to a single type of amino acid. This is called degeneracy and is exhibited as the multiplicity of three-base pair codon combinations that specify an amino acid. The genetic code is a three-letter (triplet) code defining the transfer of the information from nucleic acids to proteins. Codon is a successive string of three nucleotide and this corresponds to the amino acid sequence in the polypeptide chain. This property of the genetic code is called Colinearity. Even though one amino acid can be coded by different codes, a particular code can give rise to only to a specific amino acid and this is the unambiguous nature of the genetic code. Each codon specifies one amino acid only.
So, the correct option is 'Degeneracy - (ii) , Colinearity - (iii) , Unambiguous - (i)'.

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Species	Adenine	Guanine	Thymine	Cytosine	Uracil
P	$$21$$	$$29$$	$$21$$	$$29$$	$$0$$
Q	$$29$$	$$21$$	$$29$$	$$21$$	$$0$$
R	$$21$$	$$21$$	$$29$$	$$29$$	$$0$$
S	$$21$$	$$29$$	$$0$$	$$29$$	$$21$$
T	$$21$$	$$29$$	$$0$$	$$21$$	$$29$$

Molecular Basis of Inheritance Test - 98

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Molecular Basis of Inheritance Test - 98

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Question 1

Species P, Q and R contain single-stranded DNA; S and T cannot contain double-stranded RNA

Species P, Q and R contain double-stranded RNA; species S and T contain single-stranded RNA

Species P, Q and R cannot contain single-stranded DNA; species S contains single-stranded RNA; species T contains double-stranded RNA

Species P and Q contain double-stranded DNA; species R contains single-stranded DNA; species S contains double-stranded RNA; species T contains single-stranded RNA

Solution

Question 2

combined many of the findings of other researches also studying DNA such as Rosalind Franklin and Chargaff.

showed the double helix nature of the molecule

presented a molecule with sugar-phosphate backbones on the outside and paired bases on the inside

all of the above

Solution

Question 3

(i), (ii) and (iv)

(i) and (ii)

(iii) and (iv)

(i), (ii), (iii) and (iv)

Solution

Question 4

Solution

Question 5

Topoisomerase

Helicase

RNA primase

All of these

Solution

Question 6

Transformation

Transduction

Semi-conservative DNA replication

Central dogma

Solution

Question 7

GCTTAGGCM

CGAATCCGTT

CGAAUCCGUU

AACGGAUUCG

Solution

Question 8

Only 5 $$\rightarrow$$ 3

Only 3 $$\rightarrow$$ 5

Both (a) and (b)

None of these

Solution

Question 9

G$$_1$$

S

G$$_2$$

M

Solution

Question 10

Degeneracy - (i), Colinearity - (ii), Unambiguous - (iii)

Degeneracy - (iii) , Colinearity - (ii) , Unambiguous - (i)

Degeneracy - (ii) , Colinearity - (iii) , Unambiguous - (i)

Degeneracy - (i) , Colinearity (ii) , Unambiguous - (iii)

Solution

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