chromatin, Chromosomes and the cell nucleus

DNA wrapped around proteins to form a thread-like structure when cell not divide

When cell about to divide, the chromatin coils tighten

Is a double-stranded molecule, sides are made of sugar phosphate backbone with base pairs determining genetic information

Chromosomes are made up of DNA, which has genes. Genes are instructions to make proteins

Cell division is a process where cell divides into 2 daughter cells,each with full genetic information

Making copys of DNA

region of chromosome that holds together sister chromatids

are protective caps at the ends of chromosomes. They shorten with each cell division, contributing to aging

Telomeres, replication origins, and centromere

Protects chromosome

Ensures each chromosomes is copied

Separates chromatids during division

forming higher-order arrays.CENP-B box aids kinetochore assembly needed for division

bridge connects chromosome to spindle fibers,ensuring that chromosomes are properly separated during division (inner connect chromosome , outer connect spindle fibers )

Telomerase adds DNA repeats to chromosome ends, maintaining stability and preventing aging.

like unzipping a zipper to connect to new strands to create identical copies for new cells.

are proteins that package DNA into nucleosomes

basic structural unit of DNA packaging in eukaryotes

DNA wraps around histone proteins to form nucleosomes, which are compacted with non-histone proteins into chromatin, compacting DNA to fit in nucleus

• nucleosome core has 8 histone proteins • linker DNA that separates nucleosome core length's can be from a few nucleotide pairs to 80. • double-stranded DNA is 147 nucleotide pairs long • protein core made of eight histone molecules

histone octamer is wrapped around each other to form core.DNA then wrapped around core,forming nucleosome.N-terminal tails of histones stick out from nucleosome and impacting how tightly DNA packaging

how tightly DNA is packaged and how genes are expressed.

alters DNA structure. Acetylation loosens, methylation tightens DNA thread.

One DNA laid end to end, they would reach 2 meters

process of organizing DNA into compact structures to fit within nucleus

During mitosis,DNA is tightly packed into chromosomes to ensure accurate passing to daughter cells

Scientists use fluorescent probes binding to DNA to visualize chromosome structure,used to study regions of it

DNA loops and domains compact effectively, controlling gene expression, preserving genome structure

Genes closer to the centre are less active and vise versa

double membrane that surrounds the nucleus of a cell. It protects the cell's DNA and controls the movement of molecules in and out of the nucleus.

Gate that allows molecules to go into nucleus

Indicate proteins to enter nucleus

proteins that bind to NLS on cargo proteins. going to nuclear pore to drop it then repeating the process

Less active form, found in the cytoplasm.

More active form, found in the nucleus.

protein that converts Ran-GDP to Ran-GTP in the nucleus

converts Ran-GTP to Ran-GDP in the cytoplasm

binds to importins to release cargo protein

Importin binds to cargo with NLS and Ran-GTP.enters nucleus. Inside, Ran-GTP is broken to Ran-GDP, releasing the cargo.

Exportin binds to cargo with NES and Ran-GTP.exits nucleus. Outside, Ran-GTP is broken to Ran-GDP, releasing the cargo.

protein that controls gene expression.

NF-AT is normally inactive in the cytoplasm. When calcium levels rise, calcineurin removes phosphate groups from NF-AT, exposing a nuclear import signal. NF-AT then enters the nucleus and activates gene transcription by binding to DNA.

Regulates cholesterol levels

High cholesterol: SREBP is inactive, no cholesterol creation. Low cholesterol: SCAP senses low cholesterol, SCAP senses low cholesterol, activates SREBP. SREBP enters nucleus, activates cholesterol creates genes.

* Lamins are phosphorylated. * Nuclear envelope breaks down. * Lamins are dephosphorylated. * Nuclear envelope reforms.

protein network that supports nuclear envelope.helps maintain nuclear shape and organizes chromatin.

Lamins are rod-shaped proteins having tail domain and globular head that form dimers. These dimers assemble into nuclear lamina

Interact with membrane proteins like LBR, LAP2, Man-1, Emerin, and LAP1 to anchor nuclear lamina to inner nuclear membrane.

Mutations in lamin A gene can cause various genetic disorders like muscular dystrophies,skeletal abnormalities,accelerated aging,nerve disorders.

nucleus contains many subnuclear structures,like nucleoli for ribosome production,speckles for RNA processing,PML bodies for gene regulation,Cajal bodies for RNA modification.

is the site of ribosome biogenesis.

rDNA transcription

rRNA processing

ribosome assembly

FRAP experiments show that chromatin is relatively static, while nucleolar components are highly dynamic.