Molecular Biology Of DNA Replication Process Quiz

DNA polymerase adds a nucleotide to the 3'-OH (hydroxyl) of a primer DNA molecule. This is because DNA polymerase synthesizes DNA in the 5' to 3' direction, meaning that it adds nucleotides to the 3' end of the growing DNA strand. The 3'-OH group of the primer DNA molecule provides the necessary hydroxyl group for the formation of a phosphodiester bond with the incoming nucleotide, allowing for DNA synthesis to occur.

DNA helicase is the enzyme responsible for breaking the hydrogen bonds between the two DNA strands at the replication fork. It does this by using energy from ATP to unwind the double helix and separate the strands. Helicase is another term used to refer to DNA helicase, emphasizing its role in unwinding the DNA strands during replication.

Okazaki fragments are short DNA fragments that are synthesized on the lagging strand during DNA replication. The lagging strand is synthesized in the opposite direction of the replication fork, resulting in the need for Okazaki fragments to be synthesized in short, discontinuous segments. Therefore, Okazaki fragments are necessary for replication on the lagging strand, which is synthesized discontinuously.

Meselson and Stahl's experiment in 1958 provided evidence that DNA replication is semiconservative. This means that during replication, each new DNA molecule consists of one strand from the original DNA molecule and one newly synthesized strand. This disproved the other two options, which suggest conservative or dispersive replication, where the original DNA molecule would remain intact or be randomly distributed among the new molecules, respectively.

The short RNA molecule made at the beginning of an Okazaki fragment is called an RNA primer. This primer is necessary for DNA replication as it provides a starting point for the DNA polymerase enzyme to bind and begin synthesizing the complementary DNA strand. The RNA primer is later removed and replaced with DNA nucleotides, completing the formation of the Okazaki fragment.

When double-stranded DNA is heated to high temperatures (94-95ºC), the hydrogen bonds between the two strands break, causing the DNA to separate into two single strands. This process is known as denaturation, melting, or denaturing.

The protein that binds to single-stranded DNA to prevent it from forming secondary structures or kinking up is known as SSB, which stands for Single-Stranded DNA Binding protein. SSB plays a crucial role in DNA replication, repair, and recombination by stabilizing and protecting single-stranded DNA. It coats the DNA strand, preventing it from folding back on itself and maintaining its single-stranded state, which is essential for various cellular processes.

The main replication polymerase of E. coli is DNA polymerase III. This enzyme is responsible for synthesizing new DNA strands during replication. It is a complex enzyme made up of multiple subunits and is highly processive, meaning it can catalyze the addition of many nucleotides in a row without dissociating from the DNA template. DNA polymerase III is essential for accurate and efficient DNA replication in E. coli.

A telomere is the end of a eukaryotic chromosome. It consists of repetitive DNA sequences that protect the chromosome from degradation or fusion with neighboring chromosomes. Telomeres play a crucial role in maintaining the stability and integrity of the chromosome during cell division. As cells divide, telomeres gradually shorten, eventually leading to cell senescence or apoptosis. Therefore, telomeres are essential for preserving the genetic information and ensuring the proper functioning of cells.

Telomerase is the correct answer because it is an enzyme that plays a crucial role in the replication of the tips of eukaryotic chromosomes, known as telomeres. Telomerase helps to maintain the length and stability of telomeres by adding repetitive DNA sequences to the ends of chromosomes. This prevents the loss of genetic material during DNA replication and ensures the proper functioning of cells. Therefore, telomerase is essential for the replication and maintenance of eukaryotic chromosomes.

In Meselson and Stahl's experiment, after two generations of cell division, half of the DNA was of hybrid density. This means that one strand of the DNA molecule was made of the original heavy nitrogen isotope, while the other strand was made of the lighter nitrogen isotope. This result supported the semi-conservative model of DNA replication, where each new DNA molecule consists of one old strand and one newly synthesized strand.

Kornberg is the correct answer because he was the scientist who discovered the first DNA polymerase. He won the Nobel Prize in Physiology or Medicine in 1959 for his work on the enzymatic synthesis of DNA. His discovery paved the way for further understanding of DNA replication and the development of techniques such as polymerase chain reaction (PCR).

When single-stranded DNA is cooled to below 60ºC, it undergoes a process called annealing, hybridization, renaturing, or hybridizing. During this process, the complementary bases of the single-stranded DNA molecule pair up with each other to form a double-stranded DNA molecule. This is a crucial step in many molecular biology techniques, such as PCR and DNA sequencing, as it allows for the specific binding of DNA strands and the amplification or analysis of specific DNA sequences.

In Meselson and Stahl's experiment, after one generation, all of the DNA was of hybrid density. This suggests that DNA replication is a semi-conservative process, where each new DNA molecule consists of one strand from the original DNA molecule and one newly synthesized strand. This result supports the hypothesis proposed by Watson and Crick regarding the mechanism of DNA replication.