G3 RESTRICTION ENZYMES AND ELECTROPHORESIS

2.

All restriction enzymes require ______ as cofactor

Ca2+
Mg2+
Mn2+
Pb2+
All of the above

Correct Answer

A. Mg2+

Explanation

Restriction enzymes are proteins that cut DNA at specific sequences. They require a cofactor, which is a non-protein molecule or ion, to function properly. In this case, the correct cofactor for restriction enzymes is Mg2+ (magnesium ion). Mg2+ ions stabilize the enzyme's structure and help in the catalytic reaction that cleaves the DNA. Therefore, Mg2+ is essential for the activity of all restriction enzymes.

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3.

To incorporate fragments of foreign DNA into a plasmid vector, methods for cutting and rejoining of ssDNA are required.

TRUE
FALSE

Correct Answer

A. FALSE

Explanation

The statement is false because to incorporate fragments of foreign DNA into a plasmid vector, methods for cutting and rejoining of dsDNA (double-stranded DNA) are required, not ssDNA (single-stranded DNA).

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4.

Restriction–modiﬁcation systems occur in many bacterial species, and constitute a defense mechanism against the introduction of foreign DNA into the cell.

TRUE
FALSE

Correct Answer

A. TRUE

Explanation

Restriction-modification systems are indeed present in many bacterial species and serve as a defense mechanism against the entry of foreign DNA into the cell. These systems consist of enzymes called restriction enzymes that can recognize and cut specific DNA sequences, thereby preventing the uptake and incorporation of foreign DNA. The modification component of the system involves the addition of methyl groups to the bacterial DNA, which protects it from being recognized and cleaved by the restriction enzymes. Therefore, the statement "Restriction-modification systems occur in many bacterial species and constitute a defense mechanism against the introduction of foreign DNA into the cell" is true.

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5.

The sequence is the same, reading 5’→3’, on each strand.

Cohesive ends
‘Stickys’ ends
Palindromic sequences
Recognition sequences
Blunt ends

Correct Answer

A. Palindromic sequences

Explanation

Palindromic sequences refer to DNA sequences that read the same backwards and forwards on both strands. In this context, it means that the sequence is the same when read from 5' to 3' on each strand. This property is important in molecular biology as it allows for the formation of cohesive ends or "sticky" ends, which can be used in DNA cloning and genetic engineering techniques. These sequences are recognized by restriction enzymes, which can cut the DNA at specific recognition sequences, resulting in either cohesive or blunt ends depending on the enzyme.

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6.

Restriction enzymes recognize sites ranging in size from 4 to 8 bp or more, and may give products with _________.

Protruding 5’ end
Protruding 3’ end
Blunt ends
A or B
A or B or C

Correct Answer

A. A or B or C

Explanation

Restriction enzymes are enzymes that recognize specific DNA sequences and cut the DNA at those sequences. The given answer states that restriction enzymes can give products with protruding 5' ends, protruding 3' ends, or blunt ends. This means that after cutting the DNA, the resulting fragments can have either a single-stranded overhang at the 5' end, a single-stranded overhang at the 3' end, or no overhangs at all. Therefore, the correct answer is A or B or C, as restriction enzymes can produce fragments with any of these types of ends.

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7.

The extremely high speciﬁcity of restriction enzymes for their sites of action allows large DNA molecules and vectors to be join reproducibly into deﬁned fragments.

TRUE
FALSE

Correct Answer

A. FALSE

Explanation

The statement is false because the high specificity of restriction enzymes for their sites of action does not allow large DNA molecules and vectors to be joined reproducibly into defined fragments. Restriction enzymes are used to cleave DNA at specific recognition sites, but they do not have the ability to join DNA fragments together. This is typically done using DNA ligase or other methods of DNA recombination.

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8.

In fact, in some cases, DNA ends formed by enzymes with different recognition sequences may be compatible, provided the single-stranded tails can base-pair together.

TRUE
FALSE

Correct Answer

A. TRUE

Explanation

Different enzymes with different recognition sequences can create DNA ends that are compatible with each other if their single-stranded tails can base-pair together. This means that even though the enzymes may have different recognition sequences, the resulting DNA ends can still bind together and form a stable structure. Therefore, the statement is true.

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9.

Agarose is a protein derived from seaweed.

TRUE
FALSE

Correct Answer

A. FALSE

Explanation

Agarose is not a protein derived from seaweed. Agarose is a polysaccharide derived from seaweed, specifically from red algae. It is commonly used in molecular biology techniques such as gel electrophoresis to separate DNA fragments based on their size.

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10.

Agarose used for electrophoresis is a more puriﬁed form of the agar used to make bacterial culture plates.

TRUE
FALSE

Correct Answer

A. TRUE

Explanation

The statement is true because agarose used for electrophoresis is a more purified form of agar. Agar is a substance derived from seaweed and is commonly used in the preparation of culture plates for bacterial growth. However, for electrophoresis, a higher purity level is required to ensure accurate separation and analysis of DNA fragments. Therefore, agarose is specifically processed and purified to remove impurities and ensure its suitability for electrophoresis applications.

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G3 Restriction Enzymes And Electrophoresis

DNA termini without overhanging 3‘ or 5 ‘ ends.

Quiz Preview

All restriction enzymes require ______ as cofactor

To incorporate fragments of foreign DNA into a plasmid vector, methods for cutting and rejoining of ssDNA are required.

Restriction–modiﬁcation systems occur in many bacterial species, and constitute a defense mechanism against the introduction of foreign DNA into the cell.

The sequence is the same, reading 5’→3’, on each strand.

Restriction enzymes recognize sites ranging in size from 4 to 8 bp or more, and may give products with _________.

The extremely high speciﬁcity of restriction enzymes for their sites of action allows large DNA molecules and vectors to be join reproducibly into deﬁned fragments.

In fact, in some cases, DNA ends formed by enzymes with different recognition sequences may be compatible, provided the single-stranded tails can base-pair together.

Agarose is a protein derived from seaweed.

Agarose used for electrophoresis is a more puriﬁed form of the agar used to make bacterial culture plates.