1.5 Nucleic acids are important information-carrying molecules

What is the function of DNA in all living cells?

• Holds genetic information which codes for the amino acid sequences of polypeptides.

What is the function of RNA in all living cells?

• Transfers genetic information from DNA to ribosomes.

What two types of molecule are ribosomes made from?

• RNA and proteins.

What pentose sugar is found in a DNA nucleotide?

• Deoxyribose pentose sugar.

What pentose sugar is found in an RNA nucleotide?

• Ribose pentose sugar.

What nitrogen-containing organic bases are found in DNA?

• Adenine, thymine, guanine, or cytosine.

What nitrogen-containing organic bases are found in RNA?

• Adenine, uracil, guanine, or cytosine.

What type of reaction joins nucleotides together to form polynucleotides?

• Condensation reactions, removing water molecules.

Which groups react when two nucleotides join?

• The phosphate group of one nucleotide reacts with the deoxyribose or ribose pentose sugar of another.

What bonds are formed when nucleotides join?

• Phosphodiester bonds.

Why did many scientists initially doubt that DNA carried the genetic code?

• The relative simplicity of DNA, as it is a chemically simple molecule with few components.

What type of molecule is DNA?

• A polymer of nucleotides, known as a polynucleotide.

What three components make up a DNA nucleotide?

• Deoxyribose, a phosphate group, and a nitrogen-containing organic base.

What bonds join adjacent nucleotides in a DNA strand?

• Phosphodiester bonds.

What holds the two polynucleotide chains together?

• Two polynucleotide chains held together with hydrogen bonds between complementary base pairs.

Which bases pair together in DNA?

• Adenine pairs with thymine, and cytosine pairs with guanine.

What is the overall shape of DNA?

• A double helix.

What type of molecule is messenger RNA?

• A polymer of nucleotides, known as a polynucleotide.

What three components make up an RNA nucleotide?

• Ribose, a phosphate group, and a nitrogen-containing organic base.

What nitrogen-containing organic bases are found in RNA?

• Uracil, adenine, cytosine, and guanine.

What bonds join adjacent nucleotides in an RNA strand?

• Phosphodiester bonds.

What is the overall shape of messenger RNA?

• A single helix.

What is the advantage of DNA having two strands?

• Both strands can act as templates for semi-conservative replication.

Why is it beneficial that hydrogen bonds between bases are weak?

• Strands can be separated for replication.

How does complementary base pairing aid replication?

• It allows for accurate replication.

Why is the presence of many hydrogen bonds between bases important?

• It makes the molecule stable and strong.

What is the function of the sugar phosphate backbone?

• Sugar phosphate backbone protects the bases and hydrogen bonds.

What is the advantage of DNA being a long molecule?

• It can store lots of genetic information that codes for amino acid sequences of polypeptides.

What is the advantage of DNA being coiled into a double helix?

• It is compact.

How does the percentage of adenine in one strand relate to the percentage of thymine in the other strand?

• The percentage of adenine in strand 1 equals the percentage of thymine in strand 2, and vice versa.

How does the percentage of guanine in one strand relate to the percentage of cytosine in the other strand?

• The percentage of guanine in strand 1 equals the percentage of cytosine in strand 2, and vice versa.

Why do these relationships between bases exist?

• Because of complementary base pairing between the two strands.