Eukaryotic Chromosome Structure quiz #1 Flashcards
Eukaryotic Chromosome Structure quiz #1
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Which terms typically apply to eukaryotic chromosomes? Select all that apply: chromatin, nucleosome, heterochromatin, euchromatin, centromere, telomere, supercoiling, histone proteins.
All of these terms—chromatin, nucleosome, heterochromatin, euchromatin, centromere, telomere, supercoiling, and histone proteins—typically apply to eukaryotic chromosomes. They describe the structure, packaging, and specialized regions of eukaryotic chromosomal DNA. What is the main difference between heterochromatin and euchromatin?
Heterochromatin is tightly packed chromatin, while euchromatin is loosely packed, allowing for more gene expression. Which histone proteins make up the core of a nucleosome?
The nucleosome core consists of two copies each of histone proteins H2A, H2B, H3, and H4. What role does the histone H1 protein play in chromatin structure?
Histone H1 acts as a linker protein, connecting nucleosome cores and helping further condense the DNA. Describe the packaging progression of eukaryotic chromosomal DNA from nucleosome to chromosome.
DNA wraps around nucleosomes, which form 30 nm fibers, then condense into 250 nm fibers, ultimately forming the visible chromosome structure. What is the function of the kinetochore in chromosome segregation?
The kinetochore is a protein complex that attaches centromeres to spindle fibers, ensuring proper chromosome separation during cell division. Which histone variant is uniquely found at centromeres, and why is it important?
CENH3 is a rare histone variant found only at centromeres, crucial for forming tightly packed heterochromatin and kinetochore attachment. What is the sequence composition and structural feature found at the very end of telomeres?
Telomeres have repetitive sequences rich in A's, T's, and G's, ending with a G-rich 3' overhang that is single-stranded. How do shelterin proteins contribute to telomere stability?
Shelterin proteins bind to telomeric repeats, protecting chromosome ends from degradation and maintaining their integrity. What is the difference between positive and negative supercoiling in DNA, and which enzymes resolve these structures?
Positive supercoiling is over-rotated DNA, while negative supercoiling is under-rotated; topoisomerases, including DNA gyrase, resolve these by introducing breaks to relax or tighten the DNA.
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