Molecular Basis of Inheritance Test

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Molecular Basis of Inheritance Test - 97

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Question 1
1 / -0

Choose the correct answers from the alternatives given :
The phenmomenon known as wobble refers to

A
the movement of multiple ribosomes along the same mRNA

B
the shifting of the reading frame in a deletion or insertion mutation

C
the ability of a tRNA to pair with different codons that may differ in the third base

D
the movement of a tRNA from the A to the P site

Solution

According to wobble phenomenon or hypothesis, flexible base pairing at the third position of the codon-anticodon duplex is possible. This means a chance in the third nitrogenous base of a codon doesn't produce a different but same amino acid. Wobble phenomenon or hypothesis, thus, corresponds to the ability of a tRNA to pair with different codons that may differ in the third base. The amino acid also doesn't change.
So, the correct option is 'the ability of a tRNA to pair with different codons that may differ in the third base.'
Question 2
1 / -0

Choose the correct answers from the alternatives given :
RNA polymerase

A
can produce several polypeptide chains at one time through the creation of polysomes

B
starts transcribing at an AUG triplet on one DNA strand

C
transcribes both introns and exons

D
transcribes both DNA strands, but always in a $$5' \, \rightarrow \, 3'$$ direction

Solution

RNA polymerase transcribes both exons and introns present in DNA which are consecutively present in the RNA too, although, introns are removed by splicing in a mature mRNA. Exons are the segment of the genetic material or DNA/RNA that code for an amino acid but introns do not code for any amino acid sequence or protein. Introns have a regulatory function in both replication and transcription processes.
So, the correct option is 'transcribes both introns and exons'.
Question 3
1 / -0

What is the basis for the difference in the synthesis of the leading and lagging strand of DNA molecules?

A
Origins of replication occur only at the 5' end of the molecule

B
DNA ligase works only in the $$3' \, \rightarrow \, 5'$$ direction

C
DNA polymerase can add new nucleotides only to the 3' end of the growing strand

D
Helicases and single-strand binding proteins work at the 5' end

Solution

The new DNA strand that grows continuously in the 5' to 3' direction is called the leading strand. The basis of the difference between the leading and lagging strand is that DNA polymerase can join new nucleotides only to the 3' end of the growing strand. Okazaki fragments are formed on the lagging strand and they are joined by the activity of DNA ligase.
So, the correct option is 'DNA polymerase can join new nucleotides only to the 3' end of the growing strand'.
Question 4
1 / -0

If the length of E. coli DNA is 1.36 mm, then how many base pairs are present in E. coli?

A
$$3.6 \times 10^4$$

B
$$3.6 \times 10^6$$

C
$$4.0 \times 10^6$$

D
$$4.6 \times 10^6$$

Solution

The distance between two consecutive base pairs is 0.34x109m, the total length of double helix DNA in an organism can be calculated by multiplying the total number of base pairs with the distance between two consecutive base pairs.
the total length of double helix DNA= total number of base pairs x distance between consecutive base pairs.
1.36 = X x 0.34 x 109
X= 1.36/ 0.34x109
So, the correct option is '4.0x 106'.
Question 5
1 / -0

Choose the correct answers from the alternatives given :
Which of the following regarding DNA is not true?

A
Complementary base pairs consist of one purine and one pyrimidine

B
Side rails of the DNA double helix are made of alternating molecules of phosphate and ribose

C
Complementary base pairs are joined by hydrogen bonds

D
Amount of thymine equals the amount of adenine

Solution

According to the chargaff's rule the amount of purine is equal to the amount of pyrimidine in a DNA. The base pairing that occurs in DNA is complementary such that A bonds with T and G bonds with C, vice verse is also true. The complementary base pairs like A and T are joined with each other by double hydrogen bonds while G and C are bonded to each other with triple hydrogen bonds. The DNA double helix side rails are made of alternating phosphate and deoxyribose sugar molecules
So, the correct option is 'Side rails of the DNA double helix are made of alternating molecules of phosphate and ribose'.
Question 6
1 / -0

The human genome project involves all of the following except _________.

A
Altering the human genome

B
Physical mapping of the chromosomes

C
Sequencing of the entire nucleotide sequence of the human genome

D
Location of RFLP markers
Solution
The Human Genome Project (HGP) was launched on 1st October 1990 for sequencing the entire genome. This project had the following objectives:-
To identify all the approximately 20,000-25,000 genes in human DNA.
To determine the sequences of the 3 billion base pairs that make up human DNA.
Knowing locations of RFLP markers. Restriction fragment length polymorphism (RFLP) is a technique that exploits variations in homologous DNA sequences. The principle of RFLP markers is that any genomic DNA can be differentiated according to the presence or absence of restriction enzyme sites.
Mapping the presence of genes on different chromosomes.
So, the correct option is 'altering the human genome'.
Question 7
1 / -0

In the Watson and Crick model of DNA, the steps of the ladder are composed of

A
sugars

B
a purine and a pyrimidine

C
two purines

D
a sugar and a phosphate molecule

Solution

In the Watson and Crick model of DNA, the "steps" of the ladder are composed of a purine and pyrimidine and the “backbone” is made up of a sugar and a phosphate molecule. The model is called a double helix because of two long strands of DNA twist around each other like a twisted ladder.
So, the correct option is 'a purine and a pyrimidine'.
Question 8
1 / -0

Select the correct match of enzyme with its related function

A
DNA polymerase - Synthesis of DNA Strands

B
Helicase - Unwinding of DNA helix

C
Ligase - Joins together short DNA segments

D
All of these

Solution

DNA polymerase is the enzyme required for the addition of nucleotides into a DNA strand being synthesized from an existing strand of DNA. Helicase refers to another enzyme that functions in unwinding of the double helix structure of DNA wound around one another to result in a melted region of DNA strand to begin the replication of DNA. The joining of the short segments of DNA created during replication of the lagging strand (3' to 5') happens due to the enzyme ligase that acts as a molecular glue.
So, the correct option is 'All of these'.

Question 9

1 / -0

Which of the following differences are incorrect between leading and lagging strands of DNA?

	Leading strand	Lagging strand
(i)	It does not require DNA ligase for its growth	DNA ligase is required for joining Okazaki
(ii)	Formation of leading strand is slower	Formation of lagging strand is quite rapid.
(iii)	Its template opens in in 5 // 3 direction	Its template opens in 3 // 5 direction.
(iv)	Formation of leading strand begins immediately at the beginning of replication.	Formation of lagging strand begins a bit later than that of leading strand

(ii) and (iv) only

(ii), (iii) and (iv) only

(ii) and (iii) only

(i), (ii) and (iii) only

Solution

The synthesis of the leading strand is more rapid compared to the lagging strand synthesis as it happens at a stretch and does not involve the formation of small segments of DNA to be joined by DNA ligase. Also the template for both the strands open from the same direction which is the 3' to 5' direction and the synthesis happens in the 5' to 3' direction

So, the correct option is '(ii) and (iii) only'.

Question 10
1 / -0

Choose the correct answer from the alternatives given :
Refer to the given steps Of DNA replication.
(i) Exposure of DNA strands
(ii) Synthesis of RNA primer
(iii) Activation of deoxyribonucleotides
(iv) Chain formation
(v) Base pairing
(vi) Proof reading and DNA repair
(vii) DNA polymerase attaches at Or site
Select the correct sequence of DNA replication.

A
(vii), (iii), (i), (ii), (v), (iv), (vi)

B
(iii), (i), (vii), (ii), (v), (iv), (vi)

C
(vii), (i) ,(iii), (ii), (v), (iv), (vi)

D
(i), (iii), (ii), (vii), (v), (iv), (vi)

Solution

The process of formation of new DNA molecules from old DNA molecules is called replication of DNA. In this process, the two DNA strands separate and are exposed, activation of deoxyribonucleotides takes place, synthesis of RNA primer, DNA polymerase joins to the DNA templates, base pairing occurs, chain formation takes place, proofreading occurs.
So, the correct answer is option D.

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Molecular Basis of Inheritance Test - 97

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Molecular Basis of Inheritance Test - 97

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SHARING IS CARING

Question 1

the movement of multiple ribosomes along the same mRNA

the shifting of the reading frame in a deletion or insertion mutation

the ability of a tRNA to pair with different codons that may differ in the third base

the movement of a tRNA from the A to the P site

Solution

Question 2

can produce several polypeptide chains at one time through the creation of polysomes

starts transcribing at an AUG triplet on one DNA strand

transcribes both introns and exons

transcribes both DNA strands, but always in a $$5' \, \rightarrow \, 3'$$ direction

Solution

Question 3

Origins of replication occur only at the 5' end of the molecule

DNA ligase works only in the $$3' \, \rightarrow \, 5'$$ direction

DNA polymerase can add new nucleotides only to the 3' end of the growing strand

Helicases and single-strand binding proteins work at the 5' end

Solution

Question 4

$$3.6 \times 10^4$$

$$3.6 \times 10^6$$

$$4.0 \times 10^6$$

$$4.6 \times 10^6$$

Solution

Question 5

Complementary base pairs consist of one purine and one pyrimidine

Side rails of the DNA double helix are made of alternating molecules of phosphate and ribose

Complementary base pairs are joined by hydrogen bonds

Amount of thymine equals the amount of adenine

Solution

Question 6

Altering the human genome

Physical mapping of the chromosomes

Sequencing of the entire nucleotide sequence of the human genome

Location of RFLP markers

Solution

Question 7

sugars

a purine and a pyrimidine

two purines

a sugar and a phosphate molecule

Solution

Question 8

DNA polymerase - Synthesis of DNA Strands

Helicase - Unwinding of DNA helix

Ligase - Joins together short DNA segments

All of these

Solution

Question 9

(ii) and (iv) only

(ii), (iii) and (iv) only

(ii) and (iii) only

(i), (ii) and (iii) only

Solution

Question 10

(vii), (iii), (i), (ii), (v), (iv), (vi)

(iii), (i), (vii), (ii), (v), (iv), (vi)

(vii), (i) ,(iii), (ii), (v), (iv), (vi)

(i), (iii), (ii), (vii), (v), (iv), (vi)

Solution

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