BZ 110 1st Edition Lecture 4Outline of Last Lecture II. Organelles of eukaryotic cells continuedA. VaultsIII. Tissuesa. Tissue typesIV. Methods of Gene Regulation at the Translational LevelV. Introduction to MutationsVI. Chapter 3: cell division and inheritanceVII. Eukaryotic cell cycle and mitosisOutline of Current Lecture I. Continuation of eukaryotic cell cycle II. MitosisIII. MeiosisIV. Sources of genetic variationV. Molecular geneticsVI. Differences in DNA and RNA moleculesCurrent LectureContinuation of the eukaryotic cell cycle and mitosis- Interphase:o Includes G1, S, and G2 phaseo Cell cycle varies in length in different organisms About 18-24 hours in mammalso Occupies about 90% of the total cell cycleo G1: Period of growth, Carrying out functions to that specific cell, usually the longest phase of interphaseo S phase: replication of DNAThese 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. Replication ensures that each new cell receives identical genetic information that is present in the parent cello G2: Continues to grow and carry out the basic function of that cell and prepare for mitosisMitosis: - Mitosis: Deals with somatic cells, and is divided into 4 phases:o Prophase: Chromatin condense and chromosomes become visible. The nuclear envelope breaks down.  Centrosomes: Are microtubule organizing center of the cell, they replicate.  Centrioles: a pair of them make up a centrosome. Consist of microtubules Asters: array of microtubules that radiate from the centrosomes. Brace each centriole against the plasma membrane Mitotic spindle: include the asters, spindle, centrioles, and microtubules.o Metaphase: chromatids are aligned in the center of the cell, during late metaphase centromeres divide and detach the two sister chromatids. After the centromeres divide the sister chromatids are now considered chromosomes. o Anaphase: sister chromatids separate and are pulled to the opposite pole of the cell by the spindle fibers. By the end of anaphase each pole of cell has a chromosome.o Telophase: Occurs once the poles receive chromosomes, mitotic spindle disassembles, nuclear envelopes reform around both sets of chromosomes, cell pinches in the middle. o Usually followed by cytokinesis: cell completely divides into two identical daughter cells- Mitosis is important for growth and development, as well as serves to replace lost or damaged cells.- Humans have a diploid number of 46, and a haploid number is 23.o Diploid (N=46)o Haploid (N=23Meiosis:- Reduction division (2N1N)- Associated only with sex cellso Give rise to Gamete cells- DNA replication occurs in germ-lined diploid cells during the S phase of cell cycle- Chromosomes divide twice- Each cell gets one set of chromosomes making it haploid- When haploids fuse they form a diploid zygote- Meiosis consists of two successive nuclear divisions: Meiosis I, Meiosis II- Meiosis I: Nuclear division in which number of chromosomes is reduces giving us separate haploid daughter cells. Goes through: interphase, prophase I, Metaphase I, Anaphase I, telophase I.o Interphase I: Cell divides, DNA replication, parent cells are diploido Prophase I: Chromosomes condense and become visible, nuclear envelope breaks down, chromatids become visible, chromosomes pair up, cross over takes place. Synapsis: happens during prophase I, when two homologs pair Crossing over: happens during prophase I, genetic information is exchanged between chromatidso Metaphase I: Spindle apparatus is formed, Paired homologous chromosomes lineup at opposite sides of the metaphase plate through independent assortment Metaphase plate: Center of the cell Independent assortment: which copy of the homolog that ends up on which side of the metaphase plate is completely randomo Anaphase I: Homologous chromosomes separate and move toward each pole, soeach side of the cell receives 1 daughter cell with one complete set of chromosomeso Telophase I: Nuclear envelopes reform and cells separate through cytokinesis. - Meiosis II: nuclear division similar to mitosis where sister chromatids separate from eachother.o Interkinesis: Transition from meiosis I meiosis II is called, DNA replication does not occur- When meiosis is completed 4 haploid cells are produced.- Spermatogenesis: Produces mature sperm cells- Oogenesis: Produces a mature ovum or egg. Different from spermatogenesis because only one of four meiotic products develops a functional gameteWhat are sources of genetic variation among sexually reproducing organisms?- Crossing over which happened in prophase I- Independent assortment- Mutations- Random fertaliztionMolecular Genetic (3.4)- Central dogma of molecular biologyo DNARNAPRotien- Nucleic acids: DNA: Deoxyribonucleic acid, RNA: Ribonucleic acido Both polymers consisting of nucleotideso Neucleotides consist of: A nitrogen containing organic base Pentose sugar Phosphate groupDifference in DNA and RNA molecules:- Thymine vs. Uracil:o DNA consists of thymine o RNA consists of Uracil- Difference in pentose sugar:o DNA consists of deoxyriboseo RNA consists of Ribose- DNA molecules are double stranded- RNA molecules are single