Chapter 16: The Structural Basis of Cellular Information

These flashcards cover key terms and concepts related to DNA, chromosomes, and fundamental characteristics of genetic information as outlined in Chapter 16.

DNA

The molecule that is the source of genetic information; its structure is a double-helix.

Chromosome

Structures found in cells that carry genetic information in the form of DNA.

Nucleotide

The building block of nucleic acids, composed of a phosphate group, a sugar, and a nitrogenous base.

Purines

Nucleotide bases that have a double-ring structure; include Adenine (A) and Guanine (G).

Pyrimidines

Nucleotide bases with a single-ring structure; include Cytosine (C), Thymine (T) (in DNA), and Uracil (U) (in RNA).

Chargaff's Rules

For all organisms, the concentration of [Adenine] = [Thymine] and [Guanine] = [Cytosine].

Complementary Base Pairing

The specific pairing of nucleotide bases: Adenine (A) pairs with Thymine (T) in DNA and with Uracil (U) in RNA, and Guanine (G) pairs with Cytosine (C).

Antiparallel

The orientation of the two strands of DNA; one strand runs 5’ to 3’ and the other runs 3’ to 5’.

Histone

Proteins that help organize and package DNA into a compact structure.

Nucleosome

The structural unit of chromatin, consisting of a segment of DNA wound around a core of histone proteins.

Euchromatin

Loosely packed form of chromatin, generally associated with active transcription of DNA.

Heterochromatin

Tightly packed form of chromatin, typically transcriptionally inactive.

Nuclear Localization Signal (NLS)

A specific amino acid sequence that targets proteins to the nucleus.

Topoisomerase

An enzyme that relieves supercoiling in DNA by introducing breaks in the DNA strands.

Ploidy Level

The number of sets of chromosomes in a cell; diploid cells have two sets (2N).

Karyotype

A visual representation of the complete set of chromosomes within a cell, arranged by size and shape.

Melting Temperature (Tm)

The temperature at which half of the DNA strands are denatured.

Supercoiling

The winding of a DNA helix, which can cause tension and is often relieved by topoisomerases.

DNA Packaging

The method by which DNA is condensed and organized to fit within a cell nucleus.

DNA Structure

Refers to the double-helix formation of DNA, with complementary base pairing and directionality.