Nucleic Acids & Mutations Lecture: Structure and Levels - PDF

10-Lecture Structure levels of nucleic acids. Mutations Lecturer: Nuritdinova R.R. Toshkent-2025 Nucleic Acid Monomers of nucleic acids are nucleotides. Long polynucleotides are made from them. Nucleotides have a complex structure. They contain p...

10-Lecture Structure levels of nucleic acids. Mutations Lecturer: Nuritdinova R.R. Toshkent-2025 Nucleic Acid Monomers of nucleic acids are nucleotides. Long polynucleotides are made from them. Nucleotides have a complex structure. They contain phosphoric acid, monosaccharide and nitrogen bases. They are divided into four according to the type of nitrogenous bases. These are adenine, guanine, cytosine, thymine (uracil). There are two types of monosaccharides in nucleic acid: ribose and deoxyribose. Ribose has 5 carbon atoms in its molecule, while glucose has 6 carbon atoms.  DNA double helix - The DNA molecule has an antiparallel structure, that is, the two strands of the helix are oriented in opposite directions. Each chain has 5-' and 3'- ends. - The discovery of the DNA molecule was one of the greatest scientific achievements of the century. - Knowing the structure of DNA made it possible to understand the functions of DNA, for example, how it is copied and how the information stored in it can be used for protein synthesis. Tertiary structure of DNA  DNA tertiary structure is the spatial shape that a DNA molecule takes as it expands and contracts. This structure is different in pro- and eukaryotes. Prokaryotic DNA is bound to a small number of proteins, including histone-like ones DNA polymerase The primary enzyme that joins nucleotides together to form new complementary strands is DNA polymerase. DNA polymerase also checks each new DNA strand for errors. Quaternary structure of DNA What is a nucleosome? Nucleosome is the basic unit of DNA packaging in eukaryotic organisms. Therefore, it is the smallest compaction element of chromatin. The nucleosome is built as a drum-shaped structure around which an octamer of proteins called histones, or 146 pairs of nucleotides, is wrapped around DNA, making almost two complete turns.  What are histones?  A histone is a protein that provides structural support for a chromosome. Each chromosome contains a long molecule of DNA, which must fit into the cell nucleus. To do that, the DNA wraps around complexes of histone proteins, giving the chromosome a more compact shape. Chargaff rules In the 1950s, a biochemist named Erwin Chargaff discovered that the nitrogenous bases (A, T, S, G) are not found in equal amounts. But the amount of A is always equal to the amount of T and the amount of C is always equal to the amount of G. This discovery was crucial in establishing the model of the DNA double helix. DNA replication is semi-conservative. That is, each strand of double helix DNA acts as a template for forming two strands. Replication process  Replication is based on the principle of complementarity, that is, base pairing, and this principle is explained in Chargaff's rules: adenine (A) always pairs with thymine (T) and cytosine (S) always pairs with guanine (G). What is a mutation?  Mutation (Latin: mutare - "change, exchange") is a change in the base pairs of the genetic material of organisms. Mutation can be caused by an error in the transfer of genetic material during cell division, ultraviolet or ionizing radiation, chemical mutagens, viruses, or processes that occur under cellular control (for example, hypermutation). Mutation is essentially a change in genetic material. Mutations observed in organisms are harmful in some cases and are characterized by a violation of some function of the organism; What is a mutation?  Mutations are divided into several groups based on where they occur.  Mainly gene, chromosome, genome and cytoplasmic mutations are observed. Mutations are caused by a number of external and internal factors, as mentioned above. Mutations occur all the time in nature and are considered the primary driver of evolution.  Gene Mutation Sickle cell anemia Hereditary disease associated with a violation of the hemoglobin protein structure. Under the microscope, red blood cells have a characteristic crescent shape (sickle shape) Patients with sickle cell anemia have an increased (though not absolute) innate resistance to malaria infection. Gene Mutation Hemophilia is usually an inherited bleeding disorder in which the blood does not clot properly. This can lead to spontaneous bleeding as well as bleeding following injuries or surgery. Blood contains many proteins called clotting factors that can help to stop bleeding. The family of queen Victoria. Albinism The cause of depigmentation is a complete or partial blockade of tyrosinase, an enzyme necessary for the synthesis of melanin, a substance on which the color of tissues depends. Chromosome mutation Itis caused by a change in the size and shape of the chromosome Chromosome mutation Chromosomes are structures containing DNA wrapped around histones to form nucleosomes. The nucleosomes further condense the DNA by winding around each other to form chromatin. There are 46 human chromosomes forming 22 pairs of autosomal chromosomes and one pair of sex chromosomes.  Genome mutation Down syndrome An "extra" chromosome in the 21st pair leads to Down syndrome (karyotype is represented by chromosome -47) Genome mutation Polyploidy is the heritable condition of possessing more than two complete sets of chromosomes. Polyploids are common among plants, as well as among certain groups of fish and amphibians.  Types of Mutations Visible (morphological) - short-legged and hairless in animals, gigantism, dwarfism and albinism in humans and animals. Biochemical mutations -- metabolic disorders. For example, some types of dementia are caused by mutations in the gene responsible for tyrosine synthesis. Radiation Mutations caused by the Chernobyl explosion Scientists found that in the 25 years after the Chernobyl disaster, genetic mutations doubled the number of congenital anomalies in the descendants of people living in areas affected by radiation.  The End Thank you