5.2.3. Genetic material: chromatin and chromosomes

Chromatin and chromosomes. Genetic material

DNA can be in the form of chromatin or chromosomes depending on the cell phase.

Chromatin

The chromatin is the way that presents the DNA in the cell nucleus. It is the basic substance of eukaryotic chromosomes, which corresponds to the association of DNA, RNA and proteins found in the interphase nucleus of eukaryotic cells and that constitutes the genome of these cells. Proteins are of two types: histones and non-histone proteins.

The basic units of chromatin are nucleosomes.

The interphase chromatin provides the genetic information for the transcription and translation processes. It distinguishes:

The heterochromatin or dense chromatin (with packaging similar to the chromosome fragments of DNA that are not transcribed). It has a more compact appearance.
The euchromatin or diffuse chromatin (less packed, less stained, contains most of the active genes). This chromatin contains the DNA fragments that are transcribed.

Chromosomes

When the cell is about to divide (mitosis or meiosis), the chromatin condenses into bodies called chromosomes. Chromosomes, like chromatin, are made up of DNA associated with histones.

The number of chromosomes varies between species, but is constant in all cells of an individual.

The chromosome is a DNA molecule that contains genes, DNA segments that contain the information necessary to synthesize a protein or character of the individual.

A somatic chromosome is made up of:

Two identical chromatids from DNA duplication, which is why they are called sister chromatids.
The centromere or primary constriction is the region by which the two sister chromatids of the replicated chromosome are held together, the chromosome presenting four arms.
The kinetochore, where the microtubules of the mitotic spindle are inserted.
The satellite, segment of the chromosome separated by the secondary constriction).
The telomere is the end of the chromosome, with special properties that protect the chromosome.

Partes de un cromosoma de Familia Bautista Caceres

Chromosome shape

All somatic cells of individuals of a species have chromosomes with the same shape. To distinguish it, we will look at the centromere, which will divide the chromosome into two arms (short or p arm and long or q arm) and on the constrictions of the chromatids.

According to the position of the centromere, chromosomes are classified into:

Metacentric. The centromere is located in the middle of the chromosome and the two arms are the same length.
Submetacentric. The length of one arm of the chromosome is slightly greater than that of the other.
Acrocentric. One arm is very short (p) and the other long (q).
Telocentric or Subtelocentric. Only one arm of the chromosome can be seen as the centromere is at the end.

Tipos de cromosomas

Chromatin and chromosomes: similarities and differences

Similarities between chromatin and chromosomes:
- Chromatin and chromosomes are made up of DNA and proteins.
Differences between chromatin and chromosomes:
- Degree of condensation:
  - The chromatin is less condensed, type "pearl necklace", solenoid or loop. It has a fibrillar appearance, little compacted and very metabolically active (genes are transcribed and translated).
  - The chromosome is highly condensed and can be seen with the light microscope. The metaphase chromosome is made up of two sister chromatids joined at the centromere. It is not metabolically active.
- When does it appear:
  - The chromatin appears in the interphase, in the interphase nucleus.
  - The chromosome appears in mitosis, to distribute genetic material between cells in cell division.

Fundamental ideas about chromatin and chromosomes

DNA, depending on the cell phase, can be found in the form of chromatin or chromosomes:

Chromatin
- In the cell nucleus.
- Formed by DNA, RNA and proteins (histones) found in the interphase nucleus of eukaryotic cells.
- It is made up of a succession of nucleosomes. It contains the genetic information.
- Two forms of chromatin:
  - The heterochromatin or dense chromatin (with packaging similar to the chromosome fragments of DNA that are not transcribed).
  - The euchromatin or diffuse chromatin. This chromatin contains the DNA fragments that are transcribed.
Chromosomes
- They appear by condensation of chromatin when the cell is about to divide (mitosis or meiosis).
- Chromosomes, like chromatin, are made up of DNA associated with histones.
- The chromosome contains the genes .
- Components of a somatic chromosome:
  - Two identical chromatids from DNA duplication, which is why they are called sister chromatids. The chromatid is each of the two equal parts of a chromosome.
  - The centromere or primary constriction is the region by which the two sister chromatids of the replicated chromosome are held together, the chromosome presenting four arms.
  - The kinetochore, where the microtubules of the mitotic spindle are inserted.
  - The satellite, segment of the chromosome separated by the secondary constriction).
  - The telomere is the end of the chromosome, with special properties that protect the chromosome.

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Skip navigation Biology 2nd Baccalaureate Biology 2nd Bac. 1. Bioelements and biomolecules. Water and mineral salts 1.1. Chemical bonds in biology 1.1.1. Intramolecular bonds 1.1.1.1. Covalent bond 1.1.1.2. Ionic bond 1.1.2. Intermolecular bonds 1.1.2.1. Van der Waals forces 1.1.2.2. Hydrogen bonds 1.2. The chemical basis of life: inorganic and organic components 1.2.1. Primary bioelements 1.2.2. Secondary bioelements 1.2.3. Trace elements 1.3. The immediate principles or biomolecules 1.3.1. Water 1.3.1.1. Chemical structure of water 1.3.1.2. Properties and functions of water 1.3.2. Mineral salts 1.3.2.1. Functions of salts in solution 1.3.2.2. Colloidal solutions and dispersions 1.3.2.3. Properties of colloidal dispersions 1.3.2.4. Diffusion, osmosis and dialysis 1.3.2.4.1. Diffusion 1.3.2.4.2. Osmosis 1.3.2.4.3. Dialysis 1.4. Bibliography 2. Glucides 2.1. Glucid concept 2.2. Classification of carbohydrates 2.3. Monosaccharides 2.3.1. Trioses 2.3.1.1. Spatial isomerism or stereoisomerism 2.3.2. Tetroses 2.3.3. Pentoses 2.3.3.1. Monosaccharide cyclization 2.3.4. Hexoses 2.4. The N-glucosidic and O-glucosidic bonds 2.4.1. Substances derived from monosaccharides 2.5. Disaccharides 2.6. Polysaccharides 2.6.1. Homopolysaccharides 2.6.1.1. Reserve homopolysaccharides 2.6.1.2. Structural homopolysaccharides 2.6.2. Heteropolysaccharides 2.6.3. Heterosides 2.7. General functions of glucides 2.8. Bibliography 3. Lipids 3.1. Lipid concept 3.2. Classification of lipids 3.2.1. Fatty acids 3.2.1.1. Saturated and unsaturated fatty acids 3.2.1.2. Chemical properties of fatty acids 3.2.1.3. Physical properties of fatty acids 3.2.1.4. Fatty Acid Functions 3.2.2. Saponifiable lipids or with fatty acids 3.2.2.1. Simple lipids 3.2.2.1.1. Acylglycerides 3.2.2.1.2. Cerides 3.2.2.2. Complex lipids 3.2.2.2.1. Phospholipids 3.2.2.2.2. Glycolipids 3.2.3. Unsaponifiable lipids or without fatty acids 3.3. Lipid functions 3.4. Bibliography 4. Proteins 4.1. Introduction to proteins 4.2. Amino acids 4.2.1. Classification of amino acids 4.2.2. Properties of amino acids 4.3. The peptide bond 4.4. Protein 4.4.1. Protein structure 4.4.1.1. Primary structure of proteins 4.4.1.2. Secondary structure of proteins 4.4.1.3. Tertiary structure of proteins 4.4.1.4. Quaternary structure of proteins 4.4.2. Protein properties 4.4.3. Classification of proteins 4.4.3.1. Holoproteins 4.4.3.2. Heteroproteins 4.4.4. Protein functions 4.5. Enzymes 4.5.1. Structure of enzymes 4.5.2. The active center of enzymes 4.5.3. General Mechanism of Enzyme Catalysis 4.5.4. Regulation of enzyme activity 4.5.5. Allosteric enzymes 4.5.6. Nomenclature and classification of enzymes 4.6. The vitamins 4.6.1. Fat-soluble vitamins 4.6.2. Water soluble vitamins 4.7. Bibliography 5. Nucleotides and nucleic acids 5.1. The chemical composition of nucleic acids 5.1.1. Components of nucleic acids 5.1.2. Concept, types and functions of nucleic acids 5.1.3. Nucleosides 5.1.4. Nucleotides 5.1.4.1. Nucleotide functions 5.1.5. Nucleic acids 5.2. Deoxyribonucleic acid (DNA) 5.2.1. DNA structure 5.2.1.1. Primary structure of DNA 5.2.1.2. Secondary structure of DNA 5.2.1.3. Tertiary structure of DNA 5.2.1.3.1. Tertiary structure of DNA in prokaryotes 5.2.1.3.2. Tertiary structure of DNA in eukaryotes 5.2.1.4. Quaternary structure of DNA 5.2.2. DNA types 5.2.3. Genetic material: chromatin and chromosomes 5.2.3.1. Karyotype and karyogram 5.3. Ribonucleic acid (RNA) 5.3.1. RNA types 5.3.1.1. Transfer RNA 5.3.1.2. Messenger RNA 5.3.1.3. Ribosomal RNA 5.3.1.4. Nucleolar RNA 5.3.1.5. Small nuclear RNA 5.3.2. Functions of ribonucleic acids 5.4. Bibliography 6. Cell morphology 6.1. Cell concept 6.1.1. Cell history 6.1.2. Cell theory 6.2. Levels of cellular organization 6.2.1. General characteristics of cells 6.2.2. Prokaryotic cells 6.2.2.1. Prokaryotic cell morphology 6.2.2.2. Structure of prokaryotes 6.2.2.2.1. Bacterial capsule 6.2.2.2.2. Bacterial wall 6.2.2.2.3. Plasma membrane 6.2.2.2.4. Cytoplasm-Ribosomes-Inclusions 6.2.2.2.5. Bacterial DNA 6.2.2.2.6. Bacterial appendages 6.2.2.3. Bacteria Physiology 6.2.3. Eukaryotic cells 6.2.3.1. Animal and plant cell 6.2.3.1.1. Animal eukaryotic cell 6.2.3.1.2. Plant eukaryotic cell 6.2.3.2. Cell Evolution: Endosymbiont Theory 6.3. Size, shape and quantity 6.4. The plasma membrane 6.4.1. Chemical composition of the membrane 6.4.2. The structure of the membrane. The fluid mosaic model 6.4.3. Functions of the plasma membrane 6.4.4. Transport across the membrane 6.4.4.1. Small molecule transport 6.4.4.2. Macromolecule transport 6.4.5. Plasma membrane differentiations 6.5. The cell wall of plant cells 6.5.1. Chemical composition of the cell wall 6.5.2. Cell wall structure 6.5.3. Cell wall differentiations 6.5.4. Cell wall functions 6.6. Extracellular matrix or glucocalyx 6.7. Cytosol or hyaloplasm 6.8. The cytoskeleton 6.8.1. Microfilaments or actin filaments 6.8.2. Intermediate filaments 6.8.3. Microtubules 6.9. Cell membrane and organelle systems 6.9.1. Membrane systems 6.9.1.1. The endoplasmic reticulum 6.9.1.2. Golgi apparatus 6.9.2. Cell organelles 6.9.2.1. Lysosomes 6.9.2.2. Peroxisomes 6.9.2.3. Vacuoles 6.9.2.4. Mitochondria 6.9.2.4.1. Functions of the mitochondria 6.9.2.5. Plastids 6.9.2.5.1. Chloroplasts 6.9.2.6. Ribosomes 6.9.2.7. Centrosome 6.9.2.8. Cilia and flagella 6.10. Cell motility 6.11. The cell nucleus 6.11.1. Characteristics of the cell nucleus 6.11.2. The interphase nucleus 6.11.3. The mitotic nucleus or nucleus in division 6.12. Bibliography 7. Metabolism 7.1. Metabolism 7.1.1. Energetic Aspects of Cellular Chemical Reactions 7.2. Catabolism 7.2.1. Catabolism and obtaining energy 7.2.2. Carbohydrate catabolism 7.2.2.1. Glycolysis 7.2.2.2. Cellular respiration 7.2.2.2.1. Oxidative decarboxylation 7.2.2.2.2. Krebs cycle 7.2.2.2.3. Electron transport chain 7.2.2.2.4. Energy balance of cellular respiration 7.2.2.3. Fermentations 7.2.2.3.1. Alcoholic or ethyl fermentation 7.2.2.3.2. Lactic fermentation 7.2.2.3.3. Other types of fermentations 7.3. Anabolism 7.3.1. Autotrophic anabolism 7.3.2. Photosynthesis 7.3.2.1. Photochemical or light phase 7.3.2.1.1. Photosystems 7.3.2.1.2. Photophosphorylation 7.3.2.1.2.1. Non cyclic photophosphorylation 7.3.2.1.2.2. Cyclic photophosphorylation 7.3.2.2. Biosynthetic or dark phase 7.3.2.3. Factors influencing photosynthesis 7.3.2.4. Products of photosynthesis 7.3.3. Chemosynthesis 7.4. Bibliography 8. Cell reproduction 8.1. The cell cycle 8.1.1. Interphase 8.1.2. Cellular division 8.2. Cellular division 8.2.1. Mitosis 8.2.1.1. Prophase 8.2.1.2. Metaphase 8.2.1.3. Anaphase 8.2.1.4. Telophase 8.2.1.5. Cytokinesis 8.2.1.6. More on mitosis 8.2.2. Meiosis 8.2.2.1. Meiosis I 8.2.2.2. Meiosis II 8.2.3. Meiosis and sexual reproduction 8.2.4. Meiosis and life cycle 8.2.5. Biological importance of meiosis 8.3. Differences and similarities between mitosis and meiosis 8.4. Bibliography 9. Classical genetics 9.1. Genetics basics 9.2. Mendelian genetics 9.2.1. The method 9.2.2. Mendel's Laws 9.2.2.1. Mendel's first law or principle of uniformity in the first generation 9.2.2.2. Mendel's second law or principle of segregation 9.2.2.2.1. Backcross and test crossover 9.2.2.3. Mendel's third law or principle of independent combination 9.3. Gene interaction 9.3.1. Gene interaction between allelic genes 9.3.2. Gene interaction between non-allelic genes that influence for the same trait 9.4. Chromosomal theory of heredity 9.5. Ligation and recombination 9.6. Complex mendelism 9.6.1. Multiple allelism 9.6.1.1. Lethal genes 9.6.2. Pleiotropy 9.6.3. Expressiveness and genetic penetrance 9.7. Sex-linked inheritance 9.7.1. Y-linked inheritance 9.7.2. X-linked inheritance 9.8. Heredity influenced by sex 9.9. Bibliography 10. Molecular genetics 10.1. DNA as hereditary material 10.2. DNA replication 10.2.1. The need for DNA replication 10.2.2. First hypotheses about DNA duplication 10.2.3. Meselson and Stahl experiment 10.2.4. The sense of growth of the new strands 10.2.5. Mechanism of DNA replication 10.2.5.1. Replication in prokaryotes 10.2.5.2. Replication in eukaryotes 10.2.6. Error correction 10.2.7. Enzymes involved in replication 10.3. Gene concept 10.4. "One gene-one enzyme" theory 10.5. Transcription 10.5.1. Mechanism of transcription 10.5.1.1. Transcription in prokaryotes 10.5.1.2. Eukaryotic transcription 10.6. Translation or protein biosynthesis 10.6.1. The genetic code 10.6.2. Mechanism of translation of RNA to proteins 10.6.2.1. Translation in eukaryotes 10.7. Regulation of gene expression 10.8. Bibliography 11. Genetics and evolution 11.1. Mutations 11.2. Types of mutations 11.2.1. Gene or point mutation 11.2.2. Chromosomal or structural mutation 11.2.3. Mutation at the genomic level 11.3. Causes of mutations 11.4. Evolutionary implications of mutations 11.5. Metabolic implications of mutations 11.6. Bibliography 12. Microbiology and biotechnology 12.1. Microbiology 12.2. Viruses 12.2.1. Viral morphology 12.2.2. Viral physiology 12.2.2.1. Lytic cycle 12.2.2.2. Lysogenic cycle 12.2.2.3. Cycles of viruses of special interest 12.2.2.3.1. Flu virus life cycle 12.2.2.3.2. Life cycle of the AIDS virus 12.3. Other acellular forms 12.3.1. Viroids 12.3.2. Prions 12.4. Biotechnology 12.5. Bibliography 13. Immunology 13.1. Infection concept 13.2. Defense mechanisms against infections 13.2.1. Nonspecific mechanisms 13.2.1.1. Primary barriers: external defenses 13.2.1.2. Secondary barriers: internal defenses 13.2.2. Specific mechanisms 13.3. Immunity and immune system 13.3.1. Components of the immune system 13.3.2. Concept and nature of antigens 13.4. The immune response 13.4.1. Humoral immune response: the antibodies 13.4.1.1. Antibody-producing cells: B lymphocytes 13.4.1.2. Antibodies 13.4.1.2.1. Types of antibodies 13.4.1.2.2. Antigen-antibody reaction 13.4.1.3. Immune memory: primary and secondary responses 13.4.2. Cellular immune response: T lymphocytes 13.5. Types of immunity 13.5.1. Natural immunity 13.5.2. Artificial immunity 13.6. Immune system disorders 13.6.1. Autoimmunity 13.6.2. Hypersensitivity 13.6.3. Immunodeficiency 13.6.4. Transplants and the phenomenon of rejections 13.7. Bibliography « Previous \| Next » 5.2.3. Genetic material: chromatin and chromosomes Chromatin and chromosomes. Genetic material DNA can be in the form of chromatin or chromosomes depending on the cell phase. Chromatin The chromatin is the way that presents the DNA in the cell nucleus. It is the basic substance of eukaryotic chromosomes, which corresponds to the association of DNA, RNA and proteins found in the interphase nucleus of eukaryotic cells and that constitutes the genome of these cells. Proteins are of two types: histones and non-histone proteins. The basic units of chromatin are nucleosomes. The interphase chromatin provides the genetic information for the transcription and translation processes. It distinguishes: The *heterochromatin* or dense chromatin (with packaging similar to the chromosome fragments of DNA that are not transcribed). It has a more compact appearance. The *euchromatin* or diffuse chromatin (less packed, less stained, contains most of the active genes). This chromatin contains the DNA fragments that are transcribed. Chromosomes When the cell is about to divide (mitosis or meiosis), the chromatin condenses into bodies called chromosomes. Chromosomes, like chromatin, are made up of DNA associated with histones. The number of chromosomes varies between species, but is constant in all cells of an individual. The chromosome is a DNA molecule that contains genes, DNA segments that contain the information necessary to synthesize a protein or character of the individual. A somatic chromosome is made up of: Two identical chromatids from DNA duplication, which is why they are called sister chromatids. The centromere or primary constriction is the region by which the two sister chromatids of the replicated chromosome are held together, the chromosome presenting four arms. The kinetochore, where the microtubules of the mitotic spindle are inserted. The satellite, segment of the chromosome separated by the secondary constriction). The telomere is the end of the chromosome, with special properties that protect the chromosome. Partes de un cromosoma de Familia Bautista Caceres Chromosome shape All somatic cells of individuals of a species have chromosomes with the same shape. To distinguish it, we will look at the centromere, which will divide the chromosome into two arms (short or p arm and long or q arm) and on the constrictions of the chromatids. According to the position of the centromere, chromosomes are classified into: Metacentric. The centromere is located in the middle of the chromosome and the two arms are the same length. Submetacentric. The length of one arm of the chromosome is slightly greater than that of the other. Acrocentric. One arm is very short (p) and the other long (q). Telocentric or Subtelocentric. Only one arm of the chromosome can be seen as the centromere is at the end. Chromatin and chromosomes: similarities and differences Similarities between chromatin and chromosomes: Chromatin and chromosomes are made up of DNA and proteins. Differences between chromatin and chromosomes: Degree of condensation: The chromatin is less condensed, type "pearl necklace", solenoid or loop. It has a fibrillar appearance, little compacted and very metabolically active (genes are transcribed and translated). The chromosome is highly condensed and can be seen with the light microscope. The metaphase chromosome is made up of two sister chromatids joined at the centromere. It is not metabolically active. When does it appear: The chromatin appears in the interphase, in the interphase nucleus. The chromosome appears in mitosis, to distribute genetic material between cells in cell division. Fundamental ideas about chromatin and chromosomes DNA, depending on the cell phase, can be found in the form of chromatin or chromosomes: Chromatin In the cell nucleus. Formed by DNA, RNA and proteins (histones) found in the interphase nucleus of eukaryotic cells. It is made up of a succession of nucleosomes. It contains the genetic information. Two forms of chromatin: The heterochromatin or dense chromatin (with packaging similar to the chromosome fragments of DNA that are not transcribed). The euchromatin or diffuse chromatin. This chromatin contains the DNA fragments that are transcribed. Chromosomes They appear by condensation of chromatin when the cell is about to divide (mitosis or meiosis). Chromosomes, like chromatin, are made up of DNA associated with histones. The chromosome contains the genes . Components of a somatic chromosome: Two identical chromatids from DNA duplication, which is why they are called sister chromatids. The chromatid is each of the two equal parts of a chromosome. The centromere or primary constriction is the region by which the two sister chromatids of the replicated chromosome are held together, the chromosome presenting four arms. The kinetochore, where the microtubules of the mitotic spindle are inserted. The satellite, segment of the chromosome separated by the secondary constriction). The telomere is the end of the chromosome, with special properties that protect the chromosome. Licensed under the Creative Commons Attribution Share Alike License 4.0 « Previous \| Next » These pages are semi-automatically translated from the web Biology 2nd Baccalaureate. Biología de 2º de Bachillerato (biologia-geologia.com). 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Chromatin and chromosomes. Genetic material

Chromatin

Chromosomes

Chromosome shape