Topic 9 – Nucleic Acids & DNA Replication

Vocabulary flashcards covering key terms and enzymes related to nucleic acids, DNA/RNA structure, and DNA replication processes.

CHONP

Acronym for the five main elements found in nucleic acids: Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus.

Nucleic Acid

Polymer of nucleotides; includes DNA and RNA.

Nucleotide

Monomer of nucleic acids made of a 5-carbon sugar, a phosphate group, and a nitrogenous base.

Deoxyribose

Five-carbon sugar in DNA that lacks one oxygen atom compared with ribose (C5H10O4).

Ribose

Five-carbon sugar in RNA containing one more oxygen than deoxyribose (C5H10O5).

DNA (Deoxyribonucleic Acid)

Double-stranded nucleic acid that stores hereditary information in cells.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid that helps convert DNA information into proteins.

Phosphate Group

The identical component of every nucleotide that links sugars to form the backbone.

Nitrogenous Base

Nitrogen-containing molecule (A, T, G, C, or U) that stores genetic code and forms hydrogen bonds.

Purine

Double-ring nitrogenous base; adenine or guanine.

Pyrimidine

Single-ring nitrogenous base; cytosine, thymine, or uracil.

Adenine (A)

Purine base that pairs with thymine in DNA or uracil in RNA.

Thymine (T)

Pyrimidine base found only in DNA; pairs with adenine.

Guanine (G)

Purine base that pairs with cytosine via three hydrogen bonds.

Cytosine (C)

Pyrimidine base that pairs with guanine.

Uracil (U)

Pyrimidine base found only in RNA; replaces thymine and pairs with adenine.

Complementary Base Pair

Specific pairing of nitrogenous bases (A-T/U and G-C) via hydrogen bonds.

Hydrogen Bond

Weak attraction that holds complementary bases together in a nucleic acid strand.

Double Helix

Two antiparallel DNA strands twisted into a spiral ladder structure.

Sugar-Phosphate Backbone

Repeating chain of sugars and phosphates forming the outer sides of DNA/RNA strands.

Antiparallel

Orientation of the two DNA strands running in opposite 5′→3′ directions.

5′ End

End of a nucleic acid strand with a free phosphate on carbon 5 of the sugar.

3′ End

End of a nucleic acid strand with a free hydroxyl on carbon 3 of the sugar.

Semi-Conservative Replication

DNA copying mechanism where each daughter molecule contains one original and one new strand.

Origin of Replication

Specific DNA sequence where replication begins.

Replication Fork

Y-shaped region where parental strands are unwound by helicase.

Helicase

Enzyme that unwinds and separates DNA strands by breaking hydrogen bonds.

DNA Polymerase

Enzyme that adds nucleotides to a growing DNA strand and proofreads for errors.

Leading Strand

New DNA strand synthesized continuously toward the replication fork.

Lagging Strand

New DNA strand synthesized discontinuously away from the fork in short fragments.

RNA Primer

Short RNA segment laid down by primase to provide a 3′-OH for DNA polymerase.

Primase

Enzyme that synthesizes RNA primers on the lagging strand.

Okazaki Fragment

Short DNA fragment produced on the lagging strand during replication.

Ligase

Enzyme that seals gaps between Okazaki fragments, forming a continuous strand.

Proofreading

DNA polymerase activity that detects and corrects mismatched bases during replication.

Mutation

Permanent change in DNA sequence arising from errors not repaired during replication.

Topoisomerase

Enzyme that relieves twisting strain ahead of the replication fork in bacterial DNA.

Gyrase

Prokaryotic topoisomerase that helps relax supercoiled bacterial DNA for replication.

Supercoiled DNA

Highly twisted bacterial DNA configuration that must be relaxed before replication.

Binary Fission

Asexual cell division in prokaryotes involving replication of a circular DNA loop.

Mitosis

Eukaryotic cell division ensuring each daughter cell receives an identical set of chromosomes.