Chapter 9 Notes: DNA and RNA Structure, DNA Replication, and Chromosome Structure

Information (Genetic Material Criteria)

Must contain information to construct an entire organism

Replication (Genetic Material Criteria)

Must be accurately copied.

Transmission (Genetic Material Criteria)

Must be passed from parent to offspring and from cell to cell during cell division.

Variation (Genetic Material Criteria)

Account for differences between individuals and species.

Nucleotides

Building blocks of DNA and RNA.

Strand (Nucleic Acid Structure)

A linear polymer of nucleotides.

Double helix (Nucleic Acid Structure)

Two strands twisted together.

Chromosomes

DNA associated with different proteins.

Genome

The complete complement of genetic material in an organism.

DNA Double Helix

A double-stranded helix with outer backbone and bases on the inside, stabilized by H-bonds; follows AT/CG rule; strands are antiparallel.

Rosalind Franklin

Analyzed DNA diffraction patterns which indicated a helical structure and a uniform diameter (~2nm).

Watson and Crick

Synthesized work of others to discover the structure of DNA using data from Franklin and Chargaff.

Proposed mechanisms of DNA replication

Semiconservative mechanism, Conservative mechanism, Dispersive mechanism.

DNA Replication Overview

The 2 parental strands are separated and serve as template strands for synthesizing daughter strands, resulting in two identical double helices.

Origin of Replication

Site within a chromosome that serves as a starting point for DNA replication.

DNA helicase

Uses energy from ATP to break H-bonds between base pairs, unwinding DNA.

DNA polymerase

Covalently links nucleotides together but can only extend a pre-existing strand in a 5’ to 3’ direction.

DNA primase

Makes a complimentary primer of RNA that can be extended by DNA polymerase.

Leading strand

Made continuously, extending in the same direction that the replication fork is moving.

Lagging strand

Made as a series of small Okazaki fragments, extending in the opposite direction as the replication fork.

Chromatin

A complex of DNA and proteins that makes up eukaryotic chromosomes.

Nucleosomes

Eukaryotic DNA compacted by wrapping around histone proteins, forming a repeating structural unit.

30-nm Fiber

Nucleosomes organized into a more compact structure, dependent on Histone H1.

Loop Domains

Interactions between the 30-nm fibers and proteins such as CTCF and SMC proteins.

Heterochromatin

Highly compacted chromatin where genes are usually inactive.

Euchromatin

Less condensed chromatin.