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Transcript
Genes and Chromosomes • Humans have 46 chromosomes in all body cells called SOMATIC CELLS CELLS THAT ARE NOT BODY CELLS ARE SEX CELLS = GAMETES • You have 23 pairs of chromosomes ---each pair is called HOMOLOGOUS • In Homologous pairs each has one copy of the same characteristic One from mom and one from dad (example eye color, skin tone etc.) What is a gene? • Characteristics are forms of genes • Genes are a segment that codes for a trait • Traits can be…. – Eyecolor – Hair color Chromosome Numbers Plants 14- cucumber 40- peanut 24- pine tree 48- potato 80- sugar cane Birds 80- canary 68- dove 80- duck 78- raven Mammals 40- beaver 38- domestic cat 78- dog 48- chimpanzee 56- elephant 30- giraffe 64- horse 60- cattle 32- walrus 44- killer whale Reptiles 36- boa constrictor 22- American Toad Fish 46- small-mouth bass 84- trout Insects 6- mosquito 32- honey bee 8- drosophila (fruit fly) 446- butterfly Anatomy of a Chromosome How does 6 feet of DNA fit into each nucleus of each cell?? • Video clip: How DNA is Packaged Check your Understanding • • • • How many chromosomes do human cells have? How many pairs of chromosomes do human cells have? What are somatic cells? You have one gene for blue eyes and one gene for brown eyes. – Where did these genes come from? • What are the two halves of a single chromosome called? • What structure holds the chromatids together? • What is a gene? Cell Cycle • Cell spends… –90% of time in INTERPHASE – doing the job –10 % of time doing cell DIVISION • Cells with either divide by MITOSIS or MEIOSIS •Mitosis is for –repair, maintenance, and growth •Meiosis is for –reproduction to produce sex cells Before ANY division, each chromosome is copied exactly— during S phase of INTERPHASE •Before ANY division, each chromosome is copied exactly—during S phase of INTERPHASE Lets look at one way cells divide Mitosis: Nuclear division resulting in two identical sets of chromosomes Phases of Mitosis 1- Prophase 2- Metaphase 3- Anaphase 4- Telophase Stages of Mitosis • Prophase 1. Chromosomes become visible (coil up and get shorter and thicker) CHROMATINCHROMATID 2. Nuclear membrane disintegrates (disappears) 3. Centrioles move to opposite sides of the cell 4. Spindle fibers appear and shoot out from centrioles (longest phase) • Metaphase 1. Chromosomes migrate to equator • Centromeres align along center 2. Spindle fibers attach to each chromosome • Anaphase 1. Sister chromatids are pulled apart 2. Separate chromatids are pulled to opposite sides of the cell by spindle fibers • Telophase 1. Nuclear membrane appears around each set of chromosomes 2. Chromosomes unwind and go back to being chromatin CYTOKINESIS CYTOKINESIS • Cell membrane begins to pinch inward (furrowing) • Entire cell divides in half • Each daughter cell has… – an exact duplicate of the DNA – 46 chromosomes – 23 pairs of chromosomes • Mitosis video (7 min) Check your Understanding • How are the terms DNA, chromatin, chromosome, and genes related? • What is the name of the process by which DNA is copied? • Name, in order, the 6 stages of the cell cycle, starting with the phase cells are in most of the time • Name the phase of the cell cycle where: – – – – – – Chromosomes line up in the middle of the cell Chromosomes first become visible Spindle fibers first appear Spindle fibers attach to sister chromatids Centrioles move to opposite sides of the cell Sister chromatids get pulled apart Still checking… – Nuclear membrane disappears – Nuclear membrane reappears – Entire cell divides in half – No chromosomes are visible • How many daughter cells are created from one parent cell? – How many chromosomes does each daughter cell have? – How many pairs of chromosomes does each daughter cell have? – What is the ploidy of the daughter cells? 1: interphase 2: late interphase / beginning prophase 3: early prophase 4: mid prophase 5: late prophase 6: metaphase 7: late metaphase / early anaphase 8: anaphase 9: early telophase 10: late telophase / cytokinesis VOCABULARY TERMS Somatic Homologous Diploid Centromere Gene Chromatid Chromosome Interphase Chromatin Replication Daughter cells Mitosis Cytokinesis