DNA Structure And Replication Quiz Questions

DNA stands for Deoxyribonucleic Acid. It is a molecule that contains the genetic instructions used in the development and functioning of all known living organisms. DNA is composed of two long chains of nucleotides twisted into a double helix structure. It carries the genetic information that determines the traits and characteristics of an organism.

DNA is not a single helical structure, but rather a double helix. It consists of two strands that are twisted around each other in a helical shape. Each strand is made up of a long chain of nucleotides, and the two strands are held together by hydrogen bonds between complementary nucleotides. This double helical structure is a key feature of DNA and allows for its replication and transmission of genetic information. Therefore, the correct answer is False.

Chargraff's Rule states that in DNA, the amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine. This means that guanine always binds with cytosine and adenine always binds with thymine. This rule is fundamental in understanding the structure and replication of DNA.

DNA replicates through semi-conservative replication. In this process, the double-stranded DNA molecule separates into two strands, and each strand serves as a template for the synthesis of a new complementary strand. As a result, each new DNA molecule formed consists of one original (conserved) strand and one newly synthesized strand. This ensures the preservation of the original genetic information while allowing for the production of identical copies of DNA during cell division. Conservative replication involves the synthesis of two completely new DNA molecules, while dispersive replication results in the random distribution of original and newly synthesized DNA segments.

Adenine and guanine are both purines. Purines are one of the two types of nitrogenous bases found in DNA and RNA, the other being pyrimidines. Purines are characterized by a double-ring structure, while pyrimidines have a single-ring structure. Adenine and guanine both have a double-ring structure, making them purines. Cytosine and thymine, on the other hand, are pyrimidines.

Cytosine and thymine are pyrimidines. Pyrimidines are one of the two types of nitrogenous bases found in DNA and RNA, the other being purines. They are characterized by a single-ring structure. Adenine and guanine, on the other hand, are purines, which have a double-ring structure. Therefore, the correct answer is cytosine and thymine.

DNA always replicates from 5' to 3'. This is because DNA is composed of two strands that run in opposite directions, with one strand running from 5' to 3' and the other running from 3' to 5'. During replication, the enzyme DNA polymerase can only add nucleotides to the 3' end of the growing strand. Therefore, the new DNA strand is synthesized in the 5' to 3' direction, complementary to the original template strand. This process ensures that the genetic information is accurately copied during DNA replication.

Humans share a remarkably high percentage of their DNA with each other. The statement suggests that over 99% of our DNA is identical to that of other humans. This is supported by scientific research, which has shown that humans share a common genetic code and have many similar genes. While there may be minor variations in DNA sequences among individuals, the overall genetic makeup of humans is highly similar. Therefore, the statement is true.

Red blood cells do not contain DNA. Unlike other cells in the body, red blood cells lose their nucleus during development and therefore do not have DNA. This allows them to have more space to carry oxygen and carbon dioxide.

Only one RNA primer is needed on the leading strand during DNA replication. The RNA primer provides a starting point for DNA polymerase to begin synthesizing new DNA strands. The leading strand is continuously synthesized in the 5' to 3' direction, so only one RNA primer is required to initiate replication. In contrast, the lagging strand is synthesized in short fragments called Okazaki fragments, and each fragment requires its own RNA primer. Therefore, the number of RNA primers needed depends on the length of the lagging strand, not the leading strand.

The Meselson-Stahl experiment involved labeling DNA with heavy nitrogen (15N) and then switching to a lighter nitrogen (14N) medium to observe DNA replication. The analysis of DNA isolated after one replication cycle showed that the DNA had a mixture of both heavy and light strands, which ruled out the conservative model of DNA replication. In the conservative model, one strand of the original DNA molecule is completely conserved and used as a template for the synthesis of a new complementary strand. Since the experiment showed a mixture of heavy and light strands, it supported the semi-conservative model of DNA replication, where each new DNA molecule consists of one original strand and one newly synthesized strand. Therefore, the conservative model was eliminated as the correct answer.

The nucleotides of DNA are made up of deoxyribose sugar, phosphate, and a nitrogenous base. Deoxyribose is a type of sugar that forms the backbone of the DNA molecule, while phosphate molecules connect the sugar molecules together. The nitrogenous base, which includes adenine, thymine, cytosine, and guanine, is attached to the sugar molecule and forms the "rungs" of the DNA ladder through base pairing. This combination of deoxyribose sugar, phosphate, and nitrogenous base forms the basic building blocks of DNA.

DNA Ligase does indeed play a role in the replication of DNA by joining together the Okazaki fragments on the lagging strand. However, it does not use a glycosyl bond to do so. Instead, DNA Ligase forms a phosphodiester bond between the adjacent nucleotides, which helps to create a continuous DNA strand. Therefore, the correct answer is False.

DNA Polymerase III is responsible for adding single nucleotides to the growing DNA strand. It does this by catalyzing the formation of phosphodiester bonds between the incoming nucleotide and the existing DNA strand. This process is essential for DNA replication, as it ensures that the new DNA strand is complementary to the template strand.