1AGCT; 2 Each unreplicated chromatin in eukaryotic cells is composed of a linear DNA molecule; 3 The entire genetic information contained in the haploid chromosome set of a eukaryotic cell is called the genome

1. Single sequence: There is generally only a single copy or a few copies in the genome, and it generally has a coding function. 2. Moderately repeated sequences: The number of repetitions is between 10 and 100,000, and most do not code for proteins, forming intragenic genes. The spacer sequence between them plays an important role in gene regulation. Coding genes include: rRNA genes, tRNA genes, histone genes, ribosome genes, etc.; 3. Highly repetitive sequences: the number of repeated copies exceeds 100,000, constituting the intervals of structural genes, distributed in the telomeres and centromeric regions of chromosomes .

There are three types of functional sequences of chromatin DNA: 1. Replication source sequence: it is the starting point for DNA replication in cells; 2: Centromere sequence: it is the connection site of the two sister chromatids that have been replicated, and it is with the spindle during metaphase. The connection allows the replicated chromosomes to be evenly distributed into the two daughter cells; 3. Telomere sequence: maintains the high degree of conservation at both ends of the DNA molecule and maintains the stability of the chromosomes

1. Characteristics of histones: (1) The basic structural protein of eukaryotic chromosomes; (2) Rich in positively charged basic amino acids such as Arg, it is a basic protein and can bind tightly to acidic DNA.

2. Classification (1) Nucleosomal histones (H2A, H2B, H3 and H4): non-species and tissue specific, highly conserved in evolution, assisting DNA to curl into a stable structure of nucleosomes. (2) Connecting histones (H1) are species and tissue specific and connect nucleosomes

1. Concept: a general term for chromatin-binding proteins other than histones. 2. Characteristics: A type of negatively charged acidic protein; smaller in number but more diverse, including chromosome skeleton proteins, regulatory proteins and related enzymes involved in nucleic acid metabolism and chemical modification of chromatin.

Composition: Constitutive chromatin (constant, all in a condensed state) and facultative chromatin (sometimes converted into euchromatin)

Multilevel spiralization model

Chromosome skeleton-radial ring model

Centromere 1. Primary constriction: refers to the junction of the two sister chromatids of the metaphase chromosome, which is a lightly colored constriction that is concave inwards. 2. Centromere: The main constricted chromatin part, composed of highly repetitive heterochromatin.

Centromere-kinetochore complexes mediate spindle chromosome association

Secondary constriction is not present on all chromosomes

The satellite is a globular structure located at the end of the chromosome. The nucleolar organization area is the chromosomal region containing the rRNA gene. This part of the rRNA gene is actively transcribed, and the chromatin condensation is low and appears as lightly stained secondary scars. It is related to nucleolus formation; it is the chromosome one of the signs

Telomeres are specialized parts of the ends of chromosomes

1 Connected to rough endoplasmic reticulum, with ribosomes attached to the surface

2. The cytoplasmic surface of the outer nuclear membrane is attached with cytoskeletal components such as intermediate fiber nuclear microtubules, which are related to the positioning of the nucleus, fixation of the nucleus and maintenance of nuclear morphology.

Arranged parallel to the outer nuclear membrane, with a smooth surface

The nuclear lamina fiber structure is attached to the nucleoplasmic surface of the inner nuclear membrane, which supports the nuclear membrane.

1Definition: The space between the inner and outer nuclear membranes

2 Connected to rough endoplasmic reticulum

1 is the annular opening formed by the fusion of the inner and outer nuclear membranes

2. A protein molecular complex composed of multiple protein particles arranged in a specific way.

Structure: A layer of network sheet structure composed of high-electron-density fiber proteins located between the outside of the inner nuclear membrane and chromatin.

Composition: Composed of lamin A, lamin B, and lamin C

Function: 1 acts as a scaffold in the nucleus; 2 is closely related to the disintegration and reconstruction of the nuclear membrane; 3 is related to the condensation of chromatin into chromosomes; 4 is involved in the replication of DNA

Make DNA replication, RNA transcription and protein translation proceed at different times and spaces; maintain a relatively stable internal environment of the cell nucleus

1 Import of nucleophilic proteins

2. Nuclear export of RNA and ribosomal subunits. Export proteins are receptors that recognize transported RNA.