Chapter 16: The Structural Basis of Cellular Information: DNA, Chromosomes & the Nucleus

Vocabulary flashcards covering key concepts from Chapter 16 on DNA, chromosomes, and the structure of the nucleus.

DNA

Deoxyribonucleic acid, a molecule that carries genetic information.

Anti-parallel

Referring to the orientation of DNA strands running in opposite directions; one strand runs 5′ to 3′ and the other 3′ to 5′.

Major groove

The larger of the two grooves in the DNA double helix where proteins can bind to DNA.

Minor groove

The smaller of the two grooves in the DNA double helix.

A-DNA

A form of DNA that is right-handed, more compact, and occurs under dehydrated conditions.

B-DNA

The most common form of DNA under physiological conditions, characterized as right-handed helical.

Z-DNA

A form of DNA that is left-handed and forms under high salt concentrations or during negative supercoiling.

Supercoiling

The over-winding or under-winding of DNA, affecting its ability to unwind for replication and transcription.

Positive supercoiling

Twisting of the DNA structure that makes it easier to open, promoting transcription.

Negative supercoiling

Twisting that tightens the DNA structure, making it harder to open, builds up ahead of replication forks.

Topoisomerases

Enzymes that relieve torsional stress in DNA by cutting and rejoining DNA strands.

Nucleosomes

Units of chromatin formed by DNA wrapped around histone proteins, containing about 146 base pairs.

Euchromatin

Loosely packed chromatin that is transcriptionally active.

Heterochromatin

Tightly packed chromatin that is generally transcriptionally inactive.

Nuclear envelope

Double membrane structure surrounding the nucleus, providing a barrier.

Nuclear pore complexes

Protein structures that regulate the transport of molecules in and out of the nucleus.

Nucleolus

Dense structure within the nucleus where ribosomal RNA (rRNA) synthesis and processing occurs.

Progeria

A genetic disorder caused by mutations in the LMNA gene, leading to accelerated aging symptoms.