Nucleic Acid Structure, Chromosome Structure, and DNA Replication

These flashcards cover key vocabulary and concepts related to nucleic acid structure, chromosome organization, and the process of DNA replication as discussed in the lecture.

Nucleotides

The building blocks of DNA and RNA.

Double Helix

The two strands of DNA twisted around each other.

Phosphate Group

A chemical group consisting of a phosphorus atom bonded to four oxygen atoms; a component of nucleotides.

Deoxyribose

The sugar component of DNA nucleotides.

Nitrogenous Bases

Molecules that contain nitrogen and form the building blocks of DNA and RNA; include purines (A, G) and pyrimidines (C, T, U).

Purines

Nitrogenous bases that have a double-ring structure; adenine (A) and guanine (G).

Pyrimidines

Nitrogenous bases that have a single-ring structure; cytosine (C), thymine (T), and uracil (U).

Phosphodiester Linkage

The covalent bond that links nucleotides in DNA and RNA, forming the sugar-phosphate backbone.

Replication Fork

The Y-shaped region where the DNA strands are unwound during DNA replication.

Euchromatin

Less compacted form of chromatin, associated with gene expression.

Heterochromatin

Highly compacted form of chromatin, typically inactive in gene expression.

Origins of Replication

Specific sites where DNA replication begins.

DNA Helicase

Enzyme that unwinds the DNA double helix during replication.

DNA Primase

Enzyme that synthesizes RNA primers to initiate DNA replication.

DNA Polymerase

Enzyme that synthesizes new DNA strands by adding nucleotides.

Okazaki Fragments

Short segments of DNA synthesized on the lagging strand during DNA replication.

Leading Strand

The strand of DNA that is synthesized continuously in the direction of the replication fork.

Lagging Strand

The strand of DNA that is synthesized discontinuously as Okazaki fragments.

Telomeres

Repeated nucleotide sequences at the ends of eukaryotic chromosomes, protecting them from degradation.

Semiconservative Replication

Mechanism of DNA replication where each new DNA molecule contains one parental strand and one newly synthesized strand.

Chargaff's Rule

In any given DNA molecule, the amount of adenine (A) equals thymine (T) and the amount of guanine (G) equals cytosine (C).

RNA Primer

Short RNA sequence that provides a starting point for DNA synthesis.

DNA Ligase

Enzyme that joins together adjacent Okazaki fragments on the lagging strand.

DNA Repair Enzymes

Proteins that correct errors made during DNA replication and maintain DNA integrity.

Three Criteria for Genetic Material

1) Must contain information, 2) Must be accurately replicated, 3) Must be transmitted from cell to cell.

Genome

The complete set of genetic material in an organism.

Base Pairing

Specific hydrogen bonding between adenine & thymine (A:T) and guanine & cytosine (G:C).

Antiparallel Strands

Referring to the opposite orientation of the two strands in DNA; one runs 5’ to 3’, the other 3’ to 5’.

Major Groove

The larger of the two grooves in a double helix where protein binding can occur.

Minor Groove

The smaller of the two grooves in a double helix; less accessible to proteins.

Chromatin

The complex of DNA and protein in the nucleus of eukaryotic cells.

Chromosome

A discrete unit of genetic material composed of chromatin.

DNA Topoisomerase

Enzyme that prevents the overwinding of DNA ahead of the replication fork.

Histones

Proteins that help package DNA into nucleosomes, forming chromatin.

30-nanometer Fiber

The compact structure formed by nucleosomes organized into a more condensed form.

Nucleosome

The basic unit of DNA packaging, consisting of a segment of DNA wound around a core of histone proteins.

Replication Bubble

The opening created when DNA strands separate at the origin of replication.

Replication Origin

The site where DNA replication begins.

DNA Repair Mechanism

Includes proofreading by DNA polymerase and actions by other repair enzymes.

Template Strand

The strand of DNA that serves as a template for the synthesis of a new complementary strand.

Nucleotide Numbering System

The system that numbers the carbon atoms in the sugar of a nucleotide.

RNA Molecule

A single-stranded nucleic acid composed of ribonucleotides.

Protein Subunits

The individual protein components that form larger structures; important in chromatin assembly.

Variation

Genetic differences that may occur within and between species.

Information

The essential data encoded in DNA necessary for building organisms.