What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
- Origins of replication occur only at the 5’ end.
- Helicases and single-strand binding proteins work at the 5’end.
- DNA polymerase can join new nucleotides only to the 3’end of a pre-existing strand, and the strands are antiparallel.
- DNA ligase works only in the 3’ 5’ direction.
- The statement “Origins of replication occur only at the 5’ end” is false.
- The statement “Helicases and single-strand binding proteins work at the 5’end” is false.
- The statement “DNA polymerase can join new nucleotides only to the 3’end of a pre-existing strand, and the strands are antiparallel” is true.
- The statement “DNA ligase works only in the 3’ 5’ direction” is false.
Answer
Verified
Hint: DNA replication produces two types of new strands of DNA. One is continuous (leading strand) and other is discontinuous strand (lagging strand). DNA ligase joins lagging strands from 3’ to 5’ end while DNA polymerase helps in the synthesis of leading strands which run from 5’ to 3’ end.
Complete answer:
DNA replication is the process by which new strands are synthesized from the template strand. DNA has a double helical structure. One strand binds to the other
strand with the help of hydrogen bonds. DNA consists of many sites at which replication starts that are known as the origin of replication. One strand of the DNA runs from 3’ to 5’ end while the other end runs from 5’ to 3’ end. The 5’end has phosphate group on 5 carbon of the deoxyribose; the 3’ end contains hydroxyl group on 3 carbon of the deoxyribose.
During replication, the template strand forms two new strands: one strand is completely synthesized that is leading strand while the other
strand has discontinuous fragments. These fragments are called okazaki fragments. The leading strand synthesized in the 5’ to 3’ direction. The lagging strand synthesized in the 3’ to 5’ direction. Nucleotides of the leading strand are joined by the DNA polymerase. It only attaches at the 3’end of the growing strand. The fragments of the lagging strand are joined by DNA ligase.
From the above information we have found that ‘DNA polymerase can join new nucleotides only to the 3’ end of the
growing strand’.
Hence, the correct answer is option (C).
Note: Replication starts by unzipping of DNA helix. It is done by the helicase enzyme. A forked like structure appears when the process of DNA replication starts. DNA polymerase plays a very important role in this process as well as in transcription also.
The Elements of Life
In biology, the elements of life are the essential building blocks that make up living things. They are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. The first four of these are the most important, as they are used to construct the molecules that are necessary to make up living cells. These elements form the basic building blocks of the major macromolecules of life, including carbohydrates, lipids, nucleic acids and proteins. Carbon is an important element for all living organisms, as it is used to construct the basic building blocks of life, such as carbohydrates, lipids, and nucleic acids. Even the cell membranes are made of proteins. Carbon is also used to construct the energy-rich molecules adenosine triphosphate (ATP) and guanosine triphosphate (GTP). Hydrogen is used to construct the molecules water and organic compounds with carbon. Hydrogen is also used to construct ATP and GTP. Nitrogen is used to construct the basic building blocks of life, such as amino acids, nucleic acids, and proteins. It is also used to construct ATP and GTP. Oxygen is used to construct the basic building blocks of life, such as carbohydrates, lipids, and nucleic acids. It is also used to construct ATP and GTP. Phosphorus is used to construct the basic building blocks of life, such as carbohydrates, lipids, and nucleic acids.