Biology Chapter 10 Quiz

Comprehension Questions 10.2

• Mechanisms for compacting bacterial chromosomes include DNA supercoiling and the formation of microdomains and macrodomains.
• Negative supercoiling facilitates RNA transcription and DNA replication by promoting DNA strand separation and allowing protein binding.
• DNA gyrase promotes negative supercoiling, relaxes positive supercoils, and cuts DNA strands.

Organization of Functional Sites Along Eukaryotic Chromosomes 10.3

• Each eukaryotic chromosome has a long, linear DNA molecule.
• Species have one or more sets of chromosomes, each comprised of several unique linear chromosomes.
• Human chromosomes consist of two sets of 23 chromosomes each, totaling 46.
• A typical eukaryotic chromosome ranges in size from tens to hundreds of millions of base pairs and contains hundreds to thousands of genes.
• Genes are hundreds to tens of thousands of base pairs in length, with prokaryotic genes being much smaller.
• Eukaryotic genes frequently contain introns, non-coding intervening sequences, that can significantly increase gene length.

Sizes of Eukaryotic Genomes and Repetitive Sequences 10.4

• Eukaryotic genomes vary significantly in size, often not correlating with species complexity.
• Repetitive sequences, non-coding DNA sequences repeated numerous times, contribute to genome size differences.
• Unique sequences; found once or a few times, typically represent protein-coding genes.
• Moderately repetitive sequences; repeated hundreds to thousands of times in a genome, can include multiple copies of genes like ribosomal RNA or histone proteins.
• Highly repetitive sequences; repeated tens of thousands or millions of times, are often short and include sequences like the Alu family.

Transposition 10.5

• Transposable elements (TEs), also known as jumping genes, are DNA segments that insert into new locations in the genome.
• McClintock's studies with corn plants revealed the existence of TEs.
• Different types of TEs (transposons and retrotransposons) exist.
• Transposons move via a cut-and-paste mechanism, while retrotransposons use an RNA intermediate.
• Simple transposition involves the movement of a transposon from one site to another.
• Retrotransposition involves transcription into RNA, followed by conversion back to DNA and insertion at a new location.
• TEs may affect gene function through gene inactivation, gene regulation alterations, or chromosomal rearrangements.

Structure of Eukaryotic Chromosomes in Nondividing Cells 10.6

• Chromatin is the DNA-protein complex in eukaryotic chromosomes.
• Nucleosomes are repeating structural units of chromatin, composed of DNA wrapped around a core of histone proteins.
• The DNA wrapping within nucleosomes creates the "beads-on-a-string" structure.
• Linker histones organize adjacent nucleosomes.
• Loop domains are formed by folding of the chromatin fiber, involving interactions between nonhistone proteins and the DNA.
• Chromosome territories are the physical regions occupied by individual chromosomes in the cell nucleus.
• Chromatin structure varies between interphase and mitosis.