Presentation on theme: "Cell Structure, Mitosis and Meiosis"— Presentation transcript:
1Cell Structure, Mitosis and Meiosis Lecture 2Cell Structure, Mitosis and Meiosis
2Study Questions - Lecture 2 Describe the major components of a typical animal cell and theirfunction(s).What is the cell cycle? At which stage is the genetic material replicated? What events take place at each phase?Discuss the concepts of homologous chromosomes, diploidy, and haploidy. What characteristics are shared between two chromosomes considered to be homologous?4) What is mitosis? Describe the events that characterize each stage of mitosis.Describe how chromosomes are named on the basis of their centromere placement.What is meiosis? Describe the events that characterize each stage of meiosis.Contrast mitosis and meiosis. Explain why meiosis leads to significantgenetic variation while mitosis does not.
4Cells - “fundamental unit of life” Prokaryotes-single celled-no nucleus-no organelles-DNA = single, circular molecule- e.g., bacteriaEukaryotes-single or multicellular-nucleus with nuclear membrane-DNA packaged into chromosomes-organelles presentBiological Kingdoms: Monera, Protista, Fungi, Plantae, Animalia
7Fluid-Mosaic Model of Membrane Structure - the thing surrounding the internal components of the cellBilayer (2 layers)- of proteins and lipids
8Endoplasmic Reticulum-set of interconnected membranes. 2types.Rough ER (studded withRibosomes) - involved inproduction and modificationof proteinsSmooth ER- (no ribosomes) -involved in production oflipids, detoxification of molecules,and calcium storage in muscle cells*Ribosomes formed in nucleolus*
9Golgi ApparatusAfter proteins andlipids are made by theEndoplasmic Reticulumthey may be modifiedfurther and/or storedby the GA.
10Lysosome - formed by GA, contain enzymes that break down cellular debris and foreign substances brought into the cell
11MitochondriaAerobic respiration produces ATPHas own genome
18Cell Cycle: replication of genetic material (=DNA) and nuclear division (= mitosis + cytokinesis).
19Cell Cycle: Interphase Before mitosisTime of high metabolic activityDNA replicated and synthesizedThree phases: G1, S, and G2G1(gap 1)- longest stage of cell cycle, RNA, protein sysnthesisS (synthesis)- DNA replicated , 2 chromatids per chromosome, chromatids genetically identicalG2(gap 2)- RNA synthesis, not well understood
20Cell Cycle: MitosisProcess of cell division(nuclear division) which produces daughter cells genetically identical to the parent cellFour Phases (P-M-A-T): prophase, metaphase, anaphase, and telophase.Upon completion of the phases of mitosis (nuclear division) the cell “officially” divides into two by a process called cytokinesis - division of cytoplasm
21InterphaseNot part of mitosisDNA is replicatedchromosomes start to condense
26Anaphase*Movement of chromosomes via microtubulesto opposite sides of the cell. One chromatid to one end the otherChromatid to the opposite end
27Telophase*Genetically identical info at each pole*Spindle fibers disappear*Chromosomes uncoil*Nuclear envelope reforms aroundCytokinesis - is separate from mitosis,= pinching of cell/divison of cytoplasm.Mitosis + Cytokinesis result in twoidentical daughter cells.
30Chromosomes and Chromatids During Mitosis BeginInterphaseAfterProphaseMetaphaseAnaphasetelophase# ofChromosomes48Chromatids
31MeiosisCell division which results in halpoid “sex” cells (i.e., egg and sperm)One replication of the genetic material (DNA) during interphase, but two nuclear divisions (meiosis I and meiosis II).Results in haploid (N) cells (= gametes in animals) from an initial diploid (2N) cellVery similar to mitosis except that the cells produced are not genetically identical.