BIOL 3451 (1st Edition) Lecture 2 Outline of Last Lecture 1.1 Genetics has a Rich and Interesting History1.2 Genetics Progresses from Mendel to DNA in Less Than a Century1.3 Discovery of the Double Helix 1.4 Development of Recombinant DNA Technology Began the Era of Cloning1.5 The impact of Biotechnology is Continually Expending1.6 Genomics, Proteomics, and Bioinformatics1.7 Genetics Studies Rely on the Use of Model Organisms1.8 We Live in the Age of GeneticsOutline of Current Lecture 2.1 Cell Structure and genetic function2.2 Chromosomes Exist in Homologous pairs in Diploid Organisms2.3 Mitosis2.4 Meiosis2.5 The development of gametes2.6 Sexual reproduction in Diploid organismsCurrent Lecture2.1 Cell Structure and Genetic FunctionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Plasma membrane (all cells) Defines the cell boundary and delimits the cell from its immediate external environment.Actively controls the movement of materials into and out ofthe cell.Receptor molecules Found on the surface of the cells, act as a recognition sites that transfer specific chemical signals across the cell membrane into the cell.Glycocalyx Provides biological identity at the surface of cells.Nucleus (Eukaryotic) Membrane-bound structure that houses the genetic material, DNA.Nucleolus In the nucleus, amorphous component where ribosomal RNA (rRNA) is synthesized and where the initial stages of ribosomal assembly occur.Nucleoid Contain the circular DNA molecules, which contain the genetic material for prokaryotic organisms.Cytoplasm Includes a variety of extranuclear cellular organelles.Contain the system of tubules and filaments (support structure within the cell)Cytosol Colloidal material, surround and encompasses the cellular organellesEndoplasmic reticulum (ER) Increase the surface area available for biochemical synthesis.Smooth ER: serves as the site for synthesizing fatty acids and phospholipids.Rough ER: studded with ribosome’s.Ribosome Genetic information contained in messenger RNA (mRNA) istranslated into proteins.Mitochondria Site of the oxidative phases of cell respiration. Produce ATPChloroplasts (Plants, algae, & protozoans)Associated with photosynthesisCentrioles Located in the centrosome, associated with the organizationof spindle fibers that function if mitosis & meiosis.Spindle fibers Play an important role in the movement of chromosomes as they separate during cell division. The portions of DNA that encode rRNA are collectively referred to as the nucleolus organizer region (NOR). Prokaryotes cell do NOT have a distinct nucleolus but do contain genes that specify rRNAmolecules. Microtubules are made of the protein tubulin, and microfilament, which derive from the protein actin.2.2 Chromosomes Exist in Homologous pairs in Diploid Organisms IMPORTANT TO UNDERSTAND THE CONCEPT OFHOMOLOGOUS CHROMOSOMES. Each chromosome contains a constricted region called the centromere; the centromere location establishes thegeneral appearance of each chromosome. Depending on the centromere position, different armratios are produced. Chromosomes are classified as metacentric,submetacentric, acrocentric, or telocentric on the basis of the centromere location.  Shorter arm above the centromere is called p arm, the longer arm is q arm. ALL somatic cells derived from members of the same species contain an identical number of chromosomes. Homologous chromosome: Chromosomes that synapse or pair during meiosis and that are identical with respect to their genetic loci and centromere placement. Karyotype: The chromosome complement of a cell or an individual. Sequence according to length and centromere position. Humans: 46 chromosomes [2n2(23)] Diploid number of chromosome=2n while Haploid number of chromosome=n Genome: the genetic information of the species contained in a haploid set of chromosomes. Homologous chromosomes have important genetic similarities. Identical gene sited along their lengths. Each site is called Locus (pl. Loci) In sexual reproduction, 1 homologous chromosome comes from the mom and the otherone from the dad. Biparental inheritance: each diploid organism contains 2 copies of each gene. In a population of members of the same species, many different alternative forms of thesame gene, called alleles, can exist. During gametes formation or spores, meiosis converts the diploid number of chromosomes to the haploid number. Sex-determining chromosome: often not homologous in size, centromere placement, arm ration, or genetic content. Female have 2 “X” chromosomes, Male have 1 “X” , and 1 “Y” chromosome. “Y” chromosome is considerably smaller and lacks most of the gene loci contained on the “X”. Nevertheless, they contain homologous regions and behave has homologs in meiosis so gametes produces by males receive either one X or one Y chromosome.2.3 Mitosis In single-celled organisms (protozoans, some fungi, and algae) mitosis provides the basis for asexual reproduction. Diploid organisms (human) begin life as single-celled fertilized eggs called Zygotes. In abnormal situations, somatic cells may lose control of cell division and form a tumor. Karyokinesis: genetic material is partitioned into daughter cells during nuclear division. The end result is 2 daughter nuclei, each with a chromosome composition identical to that of the parent cell. Caryokinesis: cytoplasmic division and it follows Karyokinesis. Partitions the volume into 2 parts then encloses each new cell in a distinct plasma membrane. The amount of genetic material in the daughter cell nuclei is equivalent to that in the parent cell. Cell cycle: The events that occur from the completion of one division until the completion of the next division.The Cell Cycle(a) Interphase: The initial stage of the cell cycle (most of the cell cycle no matter what!). Thereplication of the DNA of each chromosome occurs during this stage. Also called the S phase.2 periods during interphase have NO DNA synthesis that occurs. 1 before the S phase and 1 after. Respectively called G1 and G2. By the end of G2, the volume of the cell has roughly doubled, DNA has been replicated, and mitosis is initiated.Another possibility: cell can go in G0 phase. This is like a parking for the cell, it goes to this phase if it doesn’t want to replicate no