MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

BIOLOGY

SECTION 1. BIOLOGICAL FOUNDATIONS OF HUMAN VITAL ACTIVITY

1.3. MOLECULAR-GENETIC AND CELLULAR LEVELS OF LIFE ORGANIZATION

1.3.2. Structural, chemical, and functional organization of eukaryotic cells

Levels of Organization of hereditary material and its properties

There are three levels of organization of hereditary material (DNA): Gene, chromosomal, and genomic. The elementary unit of the gene level is the gene, of the chromosomal level is the chromosome, and of the genomic level is The Genome. A gene is the functional unit of hereditary (genetic) information. Chemically, it is a segment of a DNA molecule (or RNA in some Viruses) that contains information about the Amino Acid Sequence in a polypeptide (protein) molecule or The nucleotide sequence in a ribonucleic acid molecule (rRNA or tRNA). Humans have approximately 35,000 genes (previously estimated at 50,000–100,000). Chromosomes are Structural components of the Cell Nucleus that harbor genes. The human diploid chromosome number is 46, and the haploid number is 23. The genome is the complete set of genes contained in a haploid chromosome Complement. Despite the distribution of genes across different chromosomes, all hereditary material Functions as a single, integrated system in which all levels of organization are interconnected.

Properties of hereditary material: 1) preservation; 2) Replication; 3) variation; 4) repair; 5) transmission; 6) Selection/27.html">Realization of Genetic information.

Preservation of Genetic information: the primary record of genetic information is stored in the chromosomes of The Nucleus within DNA molecules. Replication of genetic information takes place in The Cell nucleus during the S-phase of interphase prior to each Cell Division via self-duplication of DNA molecules (replication). Variation of genetic information: corresponding to the three levels of organization of hereditary material, there are Three types of its alterations (Mutations) — gene, chromosomal, and genomic. Repair: the restoration of the Introduction/19.html">Primary Structure of DNA following damage by mutagens. Transmission of genetic information: genetic information is transcribed from a DNA molecule to an mRNA molecule; mRNA transfers genetic information from its storage site (the nucleus) to the site of METABOLISM/35.html">Protein Biosynthesis (Ribosomes in the Cytoplasm). To the next generation, genetic information is transmitted via Gametes (during sexual reproduction). Realization of genetic information occurs through template-directed protein biosynthesis.