Presentation on theme: "Chapter 8: Cell Reproduction. Review OrganellesCentrioles Made of microtubules Acts as anchors in cell division Mitotic Spindle fibers Two Main types."— Presentation transcript:
Review OrganellesCentrioles Made of microtubules Acts as anchors in cell division Mitotic Spindle fibers Two Main types Kinetochore Fibers- Attach from centriole to centromere of chromosomes and assists in movement of chromosomes Polar Fibers – Extend from pole to pole and keep the shape of the cell during cell division Nuclear envelope Double Phospholipid bilayer surrounding nucleus Allows selective passage of RNA and other material Nucleolus Dense area where DNA is concentrated in the nucleus
Section 8.1 Chromosomes Chromosome Structure Rod-shaped and made of DNA and proteins called histones Two full copies of DNA Form it takes before cell division Has two identical halves called chromatid Chromatid Half of the chromosome One full copy of DNA Attached in the center Centromere Center where chromatids are held together Chromatin Less tightly coiled DNA-protein complex Tin = thin *Think spaghetti Form taken during transcription
Section 8.1 Sex Chromosomes Determine gender of the organism May carry genes for other characteristics Either X or Y Female = XX Male = XY One pair (or two chromosomes) Autosomes Remaining chromosomes Contain genes for many traits 22 pairs (or 44 chromosomes)
Section 8.1 Homologous Chromosomes Two copies of each autosome One copy from each parent Same size and shape Carry genes for the same trait Karyotype Photomicrograph of chromosomes Notice there are 22 pairs of autosomes and 1 pair of sex chromosomes What is the gender of this organism?
Section 8.1 Diploid Cells that are diploid contain two autosomes from each homologous pair and two sex chromosomes Abbreviated as 2n Memory key * di = two Occurs in all cells except sperm and egg cells Haploid Cells contain only one set of chromosomes Therefore, half the number of chromosomes of a diploid cell Abbreviated as 1n Memory key * hap = half Sperm cell (1n) and egg cell (1n) create a diploid cell (2n)
Section 8.1 Notice high number of chromosomes in fern compared to humans!
Section 8.1 Activity Create a karyotype! Arrange in pairs according to length, centromere position, and banding pattern Questions 1.How many autosomes are there? How many sex chromosomes? 2.Is the organism a male or female? 3.Why are karyotypes important tools for geneticists? Homework Review questions on p. 153 #1-5
Section 8.1 Review Answers 1.Name the proteins that DNA wraps around to form a chromosome in eukaryotic cells. Histones. Histones. 2.How do the structure and location of a prokaryotic chromosome differ from that of a eukaryotic chromosome? A prokaryotic chromosome consists of a circular DNA molecule. Eukaryotic chromosomes are rod-shaped, associated with histone and nonhistone proteins, and found within the cells nucleus. A prokaryotic chromosome consists of a circular DNA molecule. Eukaryotic chromosomes are rod-shaped, associated with histone and nonhistone proteins, and found within the cells nucleus. 3.Does chromosome number indicate whether an organism is a plant or animal? Explain. No. For example, chimpanzees have the same number of chromosomes as potatoes or plums. No. For example, chimpanzees have the same number of chromosomes as potatoes or plums.
Section 8.1 Review Answers 4. Contrast sex chromosomes with autosomes. Sex chromosomes determine the gender of an organism. Autosomes are all of the other chromosomes in an organism. Sex chromosomes determine the gender of an organism. Autosomes are all of the other chromosomes in an organism. 5. Using Table 8-1, list the haploid and diploid number of chromosomes for each organism.
Section 8.2 Cell Cycle Repeating set of events in the life of a cell Interphase Time between cell divisions Three phases G1 – Cell growth S – DNA is copied G2 – Growth and prep for cell division Cell division Two phases Mitosis – Nucleus of the cell divides Cytokinesis – Division of the cells cytoplasm
Section 8.2 Cell Division Prokaryotes Remember: Has cell wall, no nuclei, no membrane-bound organelles Binary fission Division of prokaryotic cell into two offspring cells
Section 8.2 Cell Division (contd) EukaryotesMitosis Division of the nucleus Four stages (Prophase, Metaphase, Anaphase, Telophase) Cytokinesis In animal cells, pinching of cell membrane occurs Cleavage furrow In plants, cell plate formation
Section 8.2 Control of Cell Division Checkpoints = traffic signal Three main checkpoints G1 checkpoint G2 checkpoint Mitosis checkpoint
Section 8.2 Activity Venn diagram:Cell division in Prokaryotes vs Eukaryotes Karyotype Part 2 Homework Create the cell cycle
Section 8.2 (contd) MitosisProphase Tight coiling of DNA into chromosomes Nucleolus and nuclear membrane break down Centrosomes appear and move to opposite ends of the cell Kinetochore fibers extend from kinetochore from each chromatid to centrosome Metaphase = Middle Kinetochore fibers move chromosomes to center of cell All chromosomes line up in a single file line
Section 8.2 Anaphase Chromosomes separate at the centromere and chromatids move to opposite poles Chromatids are now considered individual chromosomes Telophase Spindle fibers disassemble Chromosomes return to less tightly coiled chromatin state Nuclear envelope forms around each set of chromosomes Nucleolus forms in each of the newly forming cells Animation
Mitosis vs Meiosis Where do they occur? Mitosis – in the body cells Meiosis – in the germ cells Why does it occur? Mitosis Asexual reproduction Growth and development To replace old cells Meiosis Formation of gametes (egg and sperm cells) that will be used in sexual reproduction
Mitosis vs Meiosis End result? 46 MITOSIS 46 23 MEIOSIS
Meiosis Also known as reduction division Occurs in germ cells found in the ovaries and testes Produces sex cells which are haploid Occurs in two phases Meiosis I Reduces the number of chromosomes from diploid to haploid Meiosis II Produces four haploid daughter cells
Prophase I DNA coils tightly into chromosomes Spindle fibers appear Nucleolus and nuclear envelope disassemble Synapsis =Pairing of homologous chromosomes Tetrad =Pair of homologous chromosomes twisted around each other Crossing over may occur Genetic recombination
Meiosis I Metaphase I Spindle fibers attach to centromere of tetrads Tetrads line up along midline Anaphase I Homologous chromosome pairs are separated and move to opposite poles Independent assortment occurs Telophase I Chromosomes reach opposite ends of cell Spindle Fibers disappear Cytokinesis begins
Prophase II Spindle fibers form and attach to the centromeres of the double stranded chromosomes Metaphase II Chromosomes are moved to the midline of the dividing cell Anaphase II Chromatids separate and move toward opposite poles Telophase II Nuclear membrane forms in each of the four new cells Cytokinesis II occurs resulting in four new cells, each with half the original cells number of chromosomes