Biology - Chapter 4 Self Quiz: DNA: The Molecular Basis Of Life

Erwin Chargaff's rules, also known as Chargaff's base pairing rules, state that adenine (A) bonds with thymine (T) and cytosine (C) bonds with guanine (G). This means that in a DNA molecule, A always pairs with T, and C always pairs with G. Therefore, the statement that adenine bonds with thymine and cytosine bonds with guanine is true.

After one replication of double-stranded DNA, the daughter DNA molecules are comprised of 50% parental material.

The DNA double helix makes a complete turn every 3.4 nm along its length. This is a factual statement and is true. The double helix structure of DNA consists of two strands that are twisted around each other in a spiral shape. This twisting results in a complete turn, also known as a full rotation, every 3.4 nm. This property of DNA is important for various biological processes, including DNA replication and gene expression.

Adenine and guanine are purines.

DNA replication is semi-conservative.

Joachim Hammerling's experiment using Acetabularia demonstrated that the hereditary information is located in the foot of the alga where the nucleus resides. This suggests that the nucleus plays a crucial role in transmitting genetic material and is responsible for the hereditary traits of the organism. Hence, the statement "True" is the correct answer.

DNA polymerase III is an enzyme that ensures that the appropriate complementary base pairs have been added to the growing daughter strands during DNA replication.

DNA is a molecule that contains genetic information in living organisms. It is composed of a linear backbone made up of the sugar deoxyribose and phosphates. Nitrogenous bases, including adenine, thymine, cytosine, and guanine, are attached to the sugar residues. This structure forms the famous double helix shape of DNA. The other options do not accurately describe the composition and structure of DNA.

If the deoxynucleotide sequence in one strand of a short stretch of DNA double helix is 5'–CTGGAT–3', then the complementary sequence in the opposite strand is 3'–GACCTA–5'.

Phosphodiester bonds hold DNA’s backbone together while the complementary bases are held together by hydrogen bonds.

Okazaki fragments are short, discontinuous segments of DNA 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 these fragments to be synthesized in small pieces. DNA polymerase III is responsible for synthesizing the leading strand continuously, while DNA polymerase I is involved in removing the RNA primers and replacing them with DNA. DNA gyrase is an enzyme involved in relieving the torsional strain that builds up ahead of the replication fork. Therefore, only Okazaki fragments are specifically associated with the lagging strand during DNA replication.

DNA polymerase III builds a complementary DNA strand during DNA replication in the 5' to 3' direction.

DNA replication occurs in the 5' to 3' direction only because DNA polymerase can only add new nucleotides to the 3' end of a growing DNA strand. This means that the DNA strand being replicated is read in the 3' to 5' direction, and the new complementary strand is synthesized in the 5' to 3' direction. The leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously in short fragments called Okazaki fragments, also in the 5' to 3' direction.

The percent composition of adenine and guanine in a DNA molecule is always equal. This is because adenine always pairs with thymine and guanine always pairs with cytosine in DNA. Since adenine is found to be 35%, the percent composition of guanine would also be 35%. Therefore, the given answer of 15% is incorrect.

Matthew Meselson and Franklin Stahl's experiment illustrated that DNA replicates semiconservatively. This means that during DNA replication, each strand of the original DNA molecule serves as a template for the synthesis of a new complementary strand. As a result, each newly formed DNA molecule consists of one original strand and one newly synthesized strand. This experiment provided evidence to support the semiconservative model of DNA replication, which was proposed by James Watson and Francis Crick.

The molecule depicted in Figure 1 is a purine. Purines are heterocyclic aromatic compounds that consist of a pyrimidine ring fused with an imidazole ring. They are one of the two types of nitrogenous bases found in DNA and RNA, the other being pyrimidines. Purines include adenine and guanine, which are essential components of nucleotides and play a crucial role in the structure and function of nucleic acids.