DNA Structure and Function Concepts

DNA is the cell's information molecule, storing and transmitting heritable information through interactions between nucleotide bases. Stable base pairings, known as complementary bases, are crucial for forming double-stranded DNA, creating messenger RNA, and synthesizing proteins. Polynucleotides, the strands of DNA and RNA, are held together by covalent bonds between sugar and phosphate subunits, while hydrogen bonds form between bases. Stable hydrogen bonds depend on strand distance, base size, and geometry. Guanine pairs with cytosine, and adenine pairs with thymine or uracil. Purine-pyrimidine pairs are stable, while purine-purine and pyrimidine-pyrimidine pairs are not due to size constraints.

What is the primary role of DNA in the cell?

• To act as a structural component

• To store and transmit heritable information

• To provide energy

• To catalyze chemical reactions

Which of the following is a result of complementary base pairing?

• Creation of double-stranded DNA from a single-stranded template

• Formation of single-stranded DNA

• Breaking down of proteins

• Synthesis of lipids

What type of bonds hold the sugar and phosphate subunits together in polynucleotides?

• Ionic bonds

• Metallic bonds

• Hydrogen bonds

• Covalent bonds

What is essential for the formation of stable hydrogen bonds between nucleotide bases?

• The distance between strands, size of the bases, and geometry of each base

• The presence of metal ions

• The presence of enzymes

• The temperature of the environment

Which base pairs with adenine in RNA?

• Uracil

• Guanine

• Cytosine

• Thymine

Why do pyrimidine-pyrimidine pairings not occur?

• They are too large to fit in the space between strands

• They are not found in DNA

• They are too small to form hydrogen bonds

• They do not have the correct charge

What prevents purine-purine links from forming?

• They are too small to form hydrogen bonds

• They are not found in RNA

• They are too large to fit in the space between the polynucleotide strands

• They do not have the correct charge

What is the result of a symmetry in the structure of non-complementary purine-pyrimidine pairs?

• Formation of stable bonds

• Increased flexibility

• Crowding and prevention of stable bonds

• Enhanced stability

Which of the following is a characteristic of complementary base pairs?

• They do not form hydrogen bonds

• They involve two pyrimidines

• They always involve one purine and one pyrimidine

• They involve two purines

How many hydrogen bonds form between guanine and cytosine?

• Three

• Four

• Two

• One