Genetics Lecture Notes PDF

2/28/2023 Assistant prof. Lecturer of Medical Immunology & Molecular Genetics Department of Applied Medical Sciences College Of Medicine Univ...

2/28/2023 Assistant prof. Lecturer of Medical Immunology & Molecular Genetics Department of Applied Medical Sciences College Of Medicine University of Saba Region Gregor Mendel ( 1822 – 1884) 1  2/28/2023 Course Objectives By the end of this course the student should be able: ❖ To Know the Principles of Genetics ❖ To discriminate between Eukaryote and prokaryote ❖ To define structure and function of genes, chromosomes and genomes. ❖ To know the structure of DNA. ❖ To differentiate between RNA and DNA ❖ To discuss the mechanisms of DNA replication and repair. ❖ To know the different types of RNA. ❖ To understand the RNA Structure, Transcription, and Processing. ❖ To understand the Protein Synthesis; Translation and Posttranslational Modifications ❖ To recognize the different types mutation. ❖ To understand some changes that occur in both genes and Chromosome number and structure. ❖ To know some diseases that resulting from a genetic disorder INTRODUCTION What is a Cell? ❖ Eukaryotic cells are the cells that have a nucleus enclosed within the nuclear membrane and form large and complex organisms. ❖ All living things are composed of one or more cells. ❖ A cell is the simplest unit of life and they are responsible for keeping an organism alive and functioning. ❖ There is a massive variety of different types of cells but they all have some common characteristics. Almost every different type of cell contains genetic material, a membrane and cytoplasm. Cells also have many other features such as organelles and ribosomes that perform specific functions. 2  2/28/2023 ❑ Chemical composition by weight ❖70 % water% ❖7% small molecules salts Lipids amino acids Nucleotides DNA & RNA ❖23 % macromolecules Proteins Polysaccharides ❑Biochemical (metabolic) pathways ❑Translation of mRNA into proteins DR. FUAD ALSSAMEI Some Organelles Organelles do the work of cells. Each structure has a job to do. They keep the cell alive; keep you alive. Important organelles in this topic include the nucleus, Ribosomes, the Endoplasmic reticulum, and Mitochondria. Nucleus The control center of the cell. It contains the DNA code for the cell coiled into chromosomes. Controls all of the cellular activities DNA is inside the nucleus Surrounded by a membrane called the nuclear envelope Contains one or more nucleoli Chromosomes- are found inside the nucleus carry the information that determines what traits a living thing will have 3  2/28/2023 Some Organelles Nucleolus The dark area in the nucleus A nucleolus is composed of ribonucleic acid (RNA), and associated proteins. The nucleolus produces ribosomes, which move out of the nucleus and take a positions on the rough endoplasmic reticulum where they are critical in protein synthesis. Ribosomes ▪ Ribosomes are cellular complex machines, that are the main site for protein synthesis and are composed of proteins and ribonucleic acids. ▪ Ribosomes are made up of a small and a large subunit which coordinate with each other to translate the mRNA strand. Endoplasmic Reticulum ❖ Also known as the “ER” ❖ It is an organelle inside the cell that is made up of membranes that are in the cytoplasm of the cell ❖ There are two different ✓ Smooth ER ✓ Rough ER Type of Endoplasmic Reticulum SMOOTH ER ❖ Shaped slightly tubular and called smooth because has no ribosomes on its surface ❖ Main function is to collect, maintain & transport things ❖ Synthesizes lipids such as fatty acid and steroids ❖ Detoxifies molecules such as alcohol, drugs, and metabolic waste products ❖ Stores Ions for the cell to keep nutrients balanced Rough ER ❖ It has bumps (ribosomes) all over it giving it a “rough” appearance ❖ Bumps are called RIBOSOMES ❖ ER collects the proteins (built by the ribosomes) and creates a bubble around them ❖ VESICLE- is formed when the ER pinches off a part of its membrane 4  2/28/2023 DR. FUAD ALSSAMEI ❖ This introduction to the cell is the starting point for the area of genetics, that study how is the passes the information (traits) from one generation to the next generation? 5  2/28/2023 Definition, Structure and Function of Genetic Material ❑ Genetics is a branch of science that studies genes and hereditary (inheritance) patterns. ❖ This includes the study of chromosomes (the structure within cells that contain genes) and DNA (the building blocks of genes). ❑The genetic material is defined as A material which carries genetic information of organisms like Human, Plants, Animals and microorganisms and that passes it from one generation to the next generation. ❑ Genetic Material = DNA ❖ DNA is the genetic material of all living organisms with the exception in some viruses , which genetic material is RNA. ❖ According to the model of Watson and Crick, DNA consists of two polynucleotide chains, which form a double helix. ❖ The two strands of DNA are complementary to each other. The amount of DNA varies from person to person. ❑ The genome is the totality of genetic material (DNA) in an organism. ❖ Most DNA molecules consist of millions (3 billions) of base pairs and, consequently, many genes. ❖ Gene is the basic unit of hereditary. ❖ Allele; a variant of the DNA sequence at given locus. Each allele inherited from a different parent. 6  2/28/2023 Genomes ❑ Eukaryotic cell has 2 genomes ▪ Nuclear genome ▪ Mitochondrial genome If not specified, “genome” usually refers to the nuclear genome. ❑ In human beings genes constitute only 3 % of the human genome. ❑ The remaining 97 % of the genome – have yet no known functions! These regions are called non-coding regions. ❑ Genome = Coding regions + non-coding regions. are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Genes are contained in chromosomes, which are in the cell nucleus. Humans have about 25,000 genes. are structures within cells that contain a person's genes. A chromosome contains hundreds to thousands of genes. Every normal human cell contains 23 pairs of chromosomes, for a total of 46 chromosomes. is any gene-determined characteristic and is often determined by more than one gene. Some traits are caused by mutated genes that are inherited or that are the result of a new gene mutation. Ex: sickle cell anemia and color-blindness 7  2/28/2023 Chromosomes & Genes Genome is the complete of genetic material (DNA) in an organism. Cellular DNA is organized in chromosomes. Genes have specific places on chromosomes. DR. FUAD ALSSAMEI DNA relationship with chromosome 8  2/28/2023 DR. FUAD ALSSAMEI ❖ Chromosomes are visible under the optical microscope during metaphase, because at this stage of the cell cycle they show the highest degree of aggregation. ❖ At this stage each chromosome consists of two sister chromatids, which are retained in the centromere. ❖ The representation of chromosomes in pairs in decreasing size is called karyotype. ❖ A karyotype is a picture of the full set of chromosomes in a person’s cells. DR. FUAD ALSSAMEI 9  2/28/2023 DR. FUAD ALSSAMEI Mendelian Genetics Definitions ❖ Mendel's First Law - the law of segregation; during gamete formation each member of the allelic pair (Genotype) separates from the other member to form the genetic constitution of the gamete. ❖ This is also called Mendel’s first law of inheritance. According to the law of dominance, hybrid offspring's will only inherit the dominant trait in the phenotype. 10 2/28/2023 11  2/28/2023 Mendelian Genetics Definitions ❖ Dominant - the allele that expresses itself at the expense of an alternate allele; the phenotype that is expressed in the F1 generation from the cross of two pure lines ❖ Recessive - an allele whose expression is suppressed in the presence of a dominant allele; the phenotype that disappears in the F1 generation from the cross of two pure lines and reappears in the F2 generation 12  2/28/2023 Mendelian Genetics Definitions ❖ Allele - one alternative form of a given allelic pair; blue and brown are the alleles for the color of a eyes; more than two alleles can exist for any specific gene, but only two of them will be found within any individual ❖ Allelic pair - the combination of two alleles which comprise the gene pair (Tt) ❖ Homozygote - an individual which contains only one allele at the allelic pair (Identical alleles ); for example DD is homozygous dominant and dd is homozygous recessive; pure lines are homozygous for the gene of interest ❖ Heterozygote - an individual having two different alleles of a particular gene or genes, and so giving rise to varying offspring. for example the Dd heterozygote. ❖ Genotype - the specific allelic combination for a certain gene or set of genes 13