DNA Packaging and Telomere Structure in Eukaryotes

Positive supercoiling

Twisting that increases DNA tension.

Shelterin

Multiprotein complex protecting telomeres.

Telomeres

Caps at chromosome ends, protect from degradation.

Euchromatin

Less condensed DNA, active in transcription.

Heterochromatin

More condensed DNA, inactive in transcription.

Nucleosome

Basic unit of chromatin, consists of DNA and histones.

Chromatin

DNA and packing proteins complex in eukaryotes.

Supercoiling

Compacts DNA structure, stabilized by proteins.

Topoisomerases

Enzymes that modify DNA supercoiling.

Negative supercoiling

Twisting that decreases DNA tension.

Histone proteins

Positively charged proteins that package DNA.

Linker DNA

Stretch of DNA between nucleosomes.

T-loops

Structures formed by G-rich overhangs at telomeres.

Telomerase

Enzyme that lengthens telomeres in certain cells.

G-rich overhang

50-500 bases at telomere ends, protects DNA.

Constitutive heterochromatin

Always heterochromatic, found at centromeres.

Facultative heterochromatin

Heterochromatic only during specific developmental stages.

Histone tails

Amino acid extensions that interact with DNA.

Interphase DNA

Packed DNA during the cell's resting phase.

Cell senescence

Condition due to critically short telomeres.

Bacterial DNA

Circular chromosome located in nucleoid region.

Tertiary structure of DNA

Higher order folding and packing of DNA.

DNA polymerases

Enzymes that replicate DNA, cannot replicate ends.