Section 2
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Why do eukaryotes require complex packaging mechanisms?
Eukaryotic genomes are more complex and organized into multiple linear chromosomes, while prokaryotic genomes are contained in single circular chromosomes Eukaryotic DNA is tightly bound to histones, allowing it to fit into a small nucleus despite its extended length.
What is the basic structural unit of chromatin?
Nucleosome Nucleosomes consist of DNA wrapped around a histone octamer.
What are the five major types of histones?
• H1 • H2A • H2B • H3 • H4 Histones are small proteins that facilitate binding to negatively charged DNA.
What is the role of chromatin in eukaryotic cells?
Packages DNA and regulates gene expression Chromatin contains both histones and nonhistone proteins involved in DNA replication and gene expression.
What happens to chromatin during mitosis?
Chromatin becomes highly condensed into metaphase chromosomes This condensation allows for proper distribution of chromosomes to daughter cells.
What is the difference between euchromatin and heterochromatin?
• Euchromatin: Decondensed, transcriptionally active • Heterochromatin: Highly condensed, transcriptionally inactive Euchromatin is accessible for transcription, while heterochromatin contains repeated DNA sequences.
What is the function of centromeres during mitosis?
Attach microtubules to chromosomes and ensure correct distribution of sister chromatids Centromeres are specialized regions that play a critical role in chromosome segregation.
What is a kinetochore?
A specialized structure of proteins attached to a centromere that mediates chromosome movement Kinetochore proteins act as molecular motors during chromosome segregation.
How are centromeres defined in most eukaryotes?
By chromatin composition rather than DNA sequence The unique histone composition at centromeres is crucial for their function and stability.
What is epigenetic inheritance?
Transfer of information not based on DNA sequence, often involving histones This allows centromeres to be maintained during cell division without specific DNA sequences.
What is the role of CENP-A in centromeres?
Replaces histone H3 in centromeric chromatin and is essential for kinetochore assembly CENP-A is uniformly present at centromeres across studied organisms.