Some applications in biology, such as polymerase chain reaction (PCR), require melting the DNA double helix into single strands of DNA. This can be accomplished by heating the DNA. As DNA is heated, why does the double helix structure denature into single strands of DNA but not into individual nucleotides? In other words, why do the single strands remain intact even though the double helix does not?
Choose one:
A. The double helix is held together with phosphodiester bonds, while the single strands are linked by hydrogen bonds.
B. The single strands are wrapped around histones, which protects them from denaturing.
C. The double helix is held together with hydrogen bonds, while the single strands are linked by phosphodiester bonds.
D. The double helix structure is important for DNA replication, while the single strands carry the information.

C. The double helix is held together with hydrogen bonds, while the single strands are linked by phosphodiester bonds.

Explanation:

The double helix is formed by hydrogen bonding between the base pairs, while the single strands are linked by phosphodiester bonds.

Phosphodiester bonds are covalent bonds versus the hydrogen bonds which are noncovalent bonds. Covalent bonds are difficult to break because of electron sharing versus electrostatic attraction of hydrogen bonds.

The two major bonds of  DNA  nucleotides are  the   weaker  hydrogen bonds  between the organic bases. These bonds hold the pyrimidine and purine molecules together, to form double helix of DNA structure. The   hydrogen bonds are broken down during heating   so that   DNA double helix can  unwind to initiate gene expression Thus this bond relate DNA structures to its  functions.

Secondly the relatively stronger co-valent bonds ;phosphoster bonds between nucleotides molecules resits the applied heat. This should be  intact because  single DNA strands   need  to serve as template   to initiate  gene expression processes  so that exact copies  of DNA molecules  is transcribed to the mRNA. e.g in transcription  If these phosphodiester bonds  were broken,  then transcription will   be hindered because the DNA template  will not be available  for  mRNA  production thus  disrupting  gene expression for protein synthesis and  if during replication    new DNA synthesis will be disrupted   because of lack of DNA strands as  template.

Explanation:

Explanation:

answer; the above answer to the above statement is (true)

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.