Quiz Online 3 Chapter 4 The Tools Of The Trade

Explanation
Primase is not an enzyme used in gene manipulation. Primase is an enzyme involved in DNA replication, specifically in the synthesis of RNA primers that are necessary for DNA polymerase to initiate replication. In gene manipulation, enzymes such as endonucleases, ligases, and reverse transcriptase are commonly used. Endonucleases are used to cut DNA at specific sites, ligases are used to join DNA fragments together, and reverse transcriptase is used to convert RNA into DNA.

Explanation
Enzymes are commonly named based on the bacterium they are purified from. This naming convention helps to identify and categorize enzymes based on their source, making it easier for researchers and scientists to study and understand their properties and functions. By naming enzymes after the bacterium they are derived from, it also provides information about the potential characteristics and behavior of the enzyme. Therefore, the statement that restriction enzymes are named according to the bacterium from which they are purified is true.

Explanation
Enzymes can be bought from various suppliers.

Explanation
Restriction endonuclease is an enzyme that cuts DNA molecules at specific nucleotide sequences. It recognizes and binds to specific DNA sequences, then cleaves the DNA at or near these recognition sites. This enzyme plays a crucial role in DNA manipulation and genetic engineering techniques, as it allows for the precise cutting and manipulation of DNA molecules. Reverse transverase, DNA polymerase I, and ligase are not involved in the process of cutting DNA at specific nucleotide sequences.

Explanation
Restriction endonucleases are enzymes that can recognize specific DNA sequences and cut the DNA at those sites. This process is often referred to as molecular scissors because the enzyme acts like a pair of scissors cutting the DNA molecule at specific points. Therefore, the statement that the restriction endonuclease can be thought of as molecular scissors is true.

Explanation
Restriction mapping is a technique used to determine the positions of restriction sites in a DNA molecule by analyzing the sizes of restriction fragments. Restriction sites are specific sequences of DNA where restriction enzymes can bind and cut the DNA. By digesting the DNA with different restriction enzymes and analyzing the resulting fragments using gel electrophoresis, the positions of the restriction sites can be determined. This information is useful in studying the structure and organization of DNA, as well as in identifying genes and regulatory elements.

Explanation
Enzyme activity is not expressed in units of cleaving DNA. Enzyme activity is typically measured in units of substrate converted or product formed per unit of time. The statement that enzyme activity is expressed in units of cleaving one gram of DNA in one hour at 37◦C is incorrect.

Explanation
Reverse transcriptase is a polymerase that synthesizes DNA on an RNA template. It is an enzyme found in retroviruses and is responsible for the conversion of RNA into DNA during the process of reverse transcription. This enzyme plays a crucial role in the replication of retroviruses and is also used in molecular biology techniques such as reverse transcription polymerase chain reaction (RT-PCR) to convert RNA into complementary DNA (cDNA) for further analysis.

Explanation
Ligase is an enzyme that plays a crucial role in DNA replication, repair, and recombination processes. It is responsible for synthesizing phosphodiester bonds between adjacent nucleotides, joining the sugar-phosphate backbone of DNA strands. This enzyme is essential for sealing the gaps that occur during DNA replication and repair, ensuring the integrity and stability of the DNA molecule. Ligase is not involved in reverse transcription (Reverse transverase), DNA synthesis (DNA polymerase I), or DNA cleavage (Restriction endonuclease).

Explanation
A nuclease is an enzyme that breaks down nucleic acid molecules. It can cleave the phosphodiester bonds within the nucleic acid backbone, resulting in the degradation of the molecule. Endonucleases specifically cleave the nucleic acid at internal sites, while exonucleases cleave at the ends of the molecule. Ribonucleases are a type of nuclease that specifically degrade RNA molecules. Therefore, the correct answer is nuclease, as it is a broad term encompassing all enzymes that degrade nucleic acid molecules.