Chapter 11 – Chromosome Structure & DNA Sequence Organization

This set of flashcards covers key concepts from Chapter 11 on Chromosome Structure and DNA Sequence Organization, focusing on DNA organization in prokaryotes and eukaryotes, chromatin remodeling, histone modifications, and the nature of repetitive DNA.

What type of DNA molecules are commonly found in viruses and bacteria?

Short, circular DNA molecules relatively free of associated proteins.

How is DNA organized in eukaryotic cells?

Organized into nucleosomes and present as chromatin during most of the cell cycle.

What distinguishes interphase chromatin from mitotic chromosomes?

Interphase chromatin is uncoiled and decondensed, while mitotic chromosomes are coiled and condensed.

What are nucleosomes?

Particles with DNA wrapped around a histone octamer, essential for DNA organization.

Which proteins bind chromosomal DNA in eukaryotes?

Histones.

What is the diameter of the beads-on-a-string form of chromatin?

Approximately 10-11 nm.

What are the main types of histones found in eukaryotic chromatin?

H2A, H2B, H3, H4, and H1.

What process is important for gene expression in chromatin?

Chromatin remodeling, which is crucial for relaxing the chromatin structure.

How does acetylation affect histone tails?

It neutralizes their positive charge, relaxing their grip on DNA and increasing gene activity.

What is methylation of histone tails associated with?

It can either increase or decrease transcription depending on the context.

What is the effect of phosphorylation on histone tails?

It introduces a negative charge that can influence the cell cycle and DNA replication.

What is a CpG island?

Regions of DNA where cytosine is methylated adjacent to guanine, often silencing gene expression.

What characterizes euchromatin compared to heterochromatin?

Euchromatin is uncoiled and active, while heterochromatin is condensed and mostly inactive.

What can translocation of heterochromatin affect?

It can create a position effect that alters gene expression patterns.

What type of genetic material is found in mitochondria?

Double-stranded circular DNA that is inherited maternally.

How is chloroplast DNA described?

Circular, double-stranded, and free of associated proteins with many genes and introns.

What is a major feature of polytene chromosomes?

Paired homologs undergo multiple rounds of replication without cytoplasmic division.

Define repetitive DNA and its importance.

Abundant sequences in eukaryotic chromosomes that include multiple-copy genes; most do not encode proteins.

What role do satellite DNA and centromeric DNA sequences play?

They are important for chromosome structure and function, particularly during cell division.

What are SINEs and LINEs?

Transposable elements in the genome that can relocate; SINEs are short, while LINEs are longer and can act as retrotransposons.