Physical Basis of Heredity - Cebu Doctors' University

PHYSICAL BASIS OF HEREDITY Dr. Edelle Marie B. Tulin Assistant Professor I COLLEGE OF MEDICINE COLLEGE OF ALLIED MEDICAL SCIENCES CEBU DOCTORS’ UNIVERSITY  Table of Contents 1. Basic components of the mammalian cell 2. Human cell cycle 3. Cellular...

PHYSICAL BASIS OF HEREDITY Dr. Edelle Marie B. Tulin Assistant Professor I COLLEGE OF MEDICINE COLLEGE OF ALLIED MEDICAL SCIENCES CEBU DOCTORS’ UNIVERSITY  Table of Contents 1. Basic components of the mammalian cell 2. Human cell cycle 3. Cellular division 4. Basic structure of a human chromosome 5. Mendel’s Law of Inheritance 6. Gametogenesis and fertilization. PRE- TEST 2. 3. 1. 4. 5. CELL STRUCTURE CELL STRUCTURE Plasma membrane ○ Defines the cell boundary and delimits the cell from its immediate external environment ○ Actively controls movement into and out of the cell Cell wall ○ Plant cells ○ Cellulose - major polysaccharide component CELL STRUCTURE Glycocalyx ○ Animal cells ○ Covering of the PM ○ Glycoproteins and polysaccharide ○ Biochemical identity at the surface of cells Ex. AB, Rh antigens, histocompatibility antigens elicit an immune response Receptor molecules Eukaryotes vs Prokaryotes Eukaryotes Nucleus ○ Membrane-bound structure that houses the genetic material, DNA ○ Complexed with an array of acidic and basic proteins into thin fibers ○ Non divisional phases of the cell cycle fibers are uncoiled and dispersed into chromatin ○ Cellular division (mitosis or meiosis) Chromatin fibers coil and condense into chromosomes. Eukaryotes Nucleolus ○ Amorphous component where ribosomal RNA (rRNA) is synthesized and where the initial stages of ribosome assembly occur ○ Nucleolus organizing region (NOR) portion of DNA that encode rRNA Prokaryotes ➔ Lack a nuclear envelope and membrane organelles ➔ 2 major groups: ◆ Eubacteria ◆ Archaea Nucleoid ○ Eubacteria ○ Site where the genetic material, present as a long, circular DNA molecule is compacted Cell structure Cytoplasm ○ Extracellular nuclear organelles ○ Cytosol Nonparticulate, colloidal material Surrounds and encompass organelles ○ Cytoskeleton Provide lattice of support structures within the cell. Microtubules - derived from tubulin Microfilaments - derived from actin Maintains cell shape, facilitates cell mobility, and anchors the various organelles Cell structure Endoplasmic reticulum ○ Compartmentalizes the cytoplasm ○ Increasing the surface area available for biochemical synthesis. ○ Smooth ER site for synthesizing fatty acids and phospholipids; ○ Rough ER studded with ribosomes Cell structure Ribosomes ○ sites where genetic information contained in messenger RNA (mRNA) is translated into proteins.  Cell structure Mitochondria ○ found in most eukaryotes, including both animal and plant cells ○ Sites of the oxidative phases of cell respiration. Generate large amounts of the energy-rich molecule adenosine triphosphate (ATP). Cell structure Chloroplasts ○ found in plants, algae, and some protozoans ○ Associated with photosynthesis, the major energy-trapping process on Earth Cell structure Centriole ○ Pair of cytoplasmic bodies, each located in a specialized region called the centrosome, ○ Associated with the organization of spindle fibers that function in mitosis and meiosis. ○ In some organisms → derived from the basal body Associated with the formation of cilia and flagella (hair-like and whip-like structures for propelling cells or moving materials) Cell structure Spindle fibers ○ Organized by centrioles ○ Play an important role in the movement of chromosomes as they separate during cell division. ○ Composed of arrays of microtubules consisting of polymers of the protein tubulin CHROMOSOMES Centromere - constricted region p arm- “p” for petite q arm CHROMOSOMES MITOSIS ○ Zygote - foundation for growth and development ○ Adult - basis for wound healing and replacement of certain tissues. All somatic cells derived from the same number of species consist of identical number of chromosomes —> diploid number (2n) ○ Except sex chromosomes, exist in pairs homologous chromosomes ○ Exceptions: BACTERIA and VIRUS have only 1 chromosome CHROMOSOMES Diploid - 2n = 46 chromosomes Haploid - n = 23 chromosomes GENOME - genetic information contained in haploid LOCUS - gene sites located along homologous chromosomes BIPARENTAL INHERITANCE ○ 1 member of each pair - maternal parent (ovum) ○ Other member - paternal parent (sperm) CHROMOSOMES MEIOSIS ○ converts diploid number of chromosomes to haploid number; 2n —> n ○ following fusion of two gametes at fertilization —> diploid number is reestablished ○ EXCEPTION to concept of homologous chromosomes 1 pair = sex determining chromosomes not homologous in size, centromere placement, arm ratio, or genetic content. ○ female XX ○ male XY Short break Cell division Karyokinesis ○ nuclear division Requires great precision. Genetic material is partitioned into daughter cells; with each chromosome composition identical Cytokinesis ○ cytoplasmic division partitions the volume into two parts and then encloses each new cell in a distinct plasma membrane cytoplasm reconstituted organelles replicate themselves ○ synthesized de novo or from existing membrane structures CELL CYCLE CELL DIVISION (MITOSIS) CELL DIVISION CELL DIVISION (MITOSIS) CELL DIVISION (MITOSIS) CELL DIVISION (MITOSIS)  Cell division checkpoints Many mutations are now known that exert an effect at one or another stage of the cell cycle ○ Cell division cycle (cdc) mutations kinases cyclins Cyclins + kinase = cyclindependent kinases,. Activated kinases then phosphorylate other target proteins that regulate the progress of the cell cycle. At least 3 cell cycle checkpoints ○ Importance : DNA damage If allowed to proceed through the cell cycle ○ genetically altered cell would divide uncontrollably—> cancer If, instead, the cell cycle is arrested at one of the checkpoints ○ cell can repair the DNA damage ○ permanently stop the cell from dividing —>preventing malignancy.  CELL DIVISION (MEIOSIS) Meiosis produces gametes or spores that are characterized by only one haploid set of chromosomes. During sexual reproduction: ○ Haploid gametes then combine at fertilization to reconstitute the diploid complement found in parental cells. Meiosis must be highly specific since haploid gametes or spores must contain precisely one member of each homologous pair of chromosomes. Basis for maintaining genetic continuity from generation to generation CELL DIVISION (MEIOSIS) Underlying basis of Mendel’s principles of segregation and independent assortment. The second source of variation: ○ Crossing over - genetic exchange between members of each homologous pair of chromosomes prior to one or the other finding its way into a haploid gamete or spore. Creates intact chromosomes that are mosaics of the maternal and paternal homologs. CELL DIVISION (MEIOSIS) CELL DIVISION (MEIOSIS) CELL DIVISION (MEIOSIS) SPERMATOGENESIS vs OOGENESIS Image source: BioNinja  Thank you for your attention CREDITS: This presentation template was created by Slidesgo, and includes icons by Flaticon, and infographics & images by Freepik REFERENCE