6-2 The Cell Cycle by steepslope9876

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									Chapter 6
    Chromosomes and Cell
    Reproduction
    p. 118 - 124
Table of contents

   Chromosomes
   Karyotypes
   Cell Cycle
   Cell Cycle Control
   S-phase
   Mitosis and Cytokinesis
   Meiosis
Cells Reproduce

   Why?
    –   To repair, replace, reproduce
   How?
    –   Grow, divide, repeat
   What?
    –   DNA copied before each division
   Who?
    –   Prokaryotes = divide to reproduce
    –   Eukaryotes = divide to grow & replace
Eukaryotes:


   Chromosomes: DNA tightly
    coiled around proteins
    –   DNA has many segments called
        genes.
    –   Can only be seen during Mitosis
   Genes: code for a protein or an
    RNA molecule (single strand)
   Chromatids: the two copies of a
    chromosome
   Centromere: point where two
    chromatids are attached
Chromosomes = DNA filing cabinets
Chromosomes
   Each human cell contains 23
    pairs of chromosomes, or 46
    total.

   Every person gets one of their
    pair from each parent.

   Most chromosomes contain
    hundreds- thousands of genes.
Types of Chromosomes

    Homologous Chromosomes:
     chromosomes similar in size, shape &
     content
    Autosome: 22 chromosomes not
     deciding gender
    Sex Chromosomes: 23rd pair determine
     sex of offspring
     –   XX =
     –   XY =
Karyotype:

   Picture of the entire set of chromosomes.
    – Can detect abnormalities
         Monosomy =
         Trisomy =
Normal
Monosomy
Trisomy
Haploid vs Diploid

   Diploid
    –   (di = ______ ploid = chromosome)
    –   One from _______ and one from _______
    –   We are diploid
            We have ______ pairs of chromosomes
            _____ chromosomes all together
   Haploid
    –   One copy
    –   Simple organisms that reproduce asexually
    –   To remember – “if you’re single, you’re HAPpy”
    –   The only cells in humans that are haploid are __?__
Haploid + Haploid = Diploid
Chromosome Mutations




   Deletion – delete part
   Duplication – duplicate part
   Inversion – Flip part
   Translocation – Transfer part to other
6-2 The Cell Cycle




        p. 125 - 127
    Cell Cycle – purpose: to make more cells


   There are three major stages in the cell cycle
    –   Interphase (G1, S, G2)
    –   Mitosis
    –   Cytokinesis
•       Interphase
    –        3 stages of Interphase – 98% of cell life
         •     G1 : Cell grows
         •     S: DNA copied
         •     G2: Organelles copied
•       Mitosis
    –        Process in that the nucleus divides into two nuclei
             with the same number of chromosomes


•       Cytokinesis
    –        Process where the cytoplasm divides forming two
             separate cells.
The Cell Cycle
Controlling the Cell Cycle

   How do cells know when to divide??
    –   Brain and hormone controlled
    –   Checkpoints: Green Next Phase
             (yellow)/Red Stays in current phase longer
Checkpoints:

1) Cell Growth (G1 ) Checkpoint: Tells cell to
    divide or not
   –   Cell must be healthy and large enough
   –   Green S Phase
   –   Red Wait to grow or eliminated
   –   Some cells “rest” forever (muscle, nerve) . This is
       called “G0”
Checkpoints cont’d

2) DNA Synthesis (G2) Checkpoint:
  –   DNA copy is checked by repair enzymes
  –   Green Mitosis
  –   Red Repair DNA or eliminate cell
3) Mitosis Checkpoint: Everything organized?
  –   Green Cytokinesis
  –   Red Cell eliminated
ooooo... cell cycle
CANCER:

   Genes contain info. to make the checkpoint
    proteins that regulate cell division
   If regulatory proteins are mutated
    –   Function Improperly
    –   Cell Regulation disrupted
    –   CANCER: uncontrollable growth of cells
    –   Mutations can occur:
            Spontaneously
            Environmental Influences
When done with quiz – on back

   How are chromosomes like filing cabinets?
   What do the following mean?
    –   Monosomy?
    –   Trisomy?
   How can a karyotype help diagnose down
    syndrome?
Section 9-3


     S- Phase: DNA
     Replication
     P 196 - 198
DNA Replication

   AKA: DNA copying, DNA synthesis, DNA
    duplication

   WHY?: To produce enough DNA for two cells
    (after S phase = ____?____ )

   Where?: In the nucleus
How DNA Replication works:

1.    DNA unwinds
     a.   breaking the H-bonds
     b.   DNA Helicase.
     c.   Replication Forks (where it unzips).
2.    DNA Polymerase attaches to the DNA
     a.   adds in strands by adding complementary
          bases.
          A=T           C=G
3.    DNA Ligase
     a.   glues the DNA back together. (H-bonds)


4.    Another DNA polymerase
     a.   checks for errors.


                  T=GA
mmm...
DNA
6-3 Mitosis & Cytokinesis



            M-phase and C-phase
            p. 128 - 132
Step 2 of Cell Cycle - Mitosis

   P M A T ( Prophase, Metaphase,
           Anaphase & Telophase)
   Prophase = Pieces:
    –   Nuclear envelope breaks down
    –   Spindle fibers form (proteins)
    –   Chromosomes coil and become visible
MMMMMMMMMITOSISSSSSS!
• Metaphase: Middle
  – Spindle fibers attach to chromosomes
  – Chromosomes move to the center of the cell
• Anaphase: Away
  – Centromeres divide
  – Two chromatids (now called chromosomes)
    move to opposite poles
• Telophase: Two
  – Cytoplasmic division begins
  – Nuclear envelope reforms
  – Chromosomes uncoil
Step 3 of Cell Cycle - Cytokinesis

    Cytokinesis:
     –   Animals – cleavage furrow forms as the cell
         membrane grows together to complete division
     –   Plants – vesicles fuse together to form a cell
         plate and a new cell wall grows on either side
7-1 & 7-2 Meiosis

        Making haploid sex
        cells
        p. 142 - 152
Genetic Variation

   Why Important?
   How Created?
    –   Random fertilization
    –   Independent assortment
    –   Crossing over
Asexual vs. Sexual

   Asexual – one parent - produces identical
    offspring
   Sexual – two parents – produces genetic
    variations
Prophase I

   Crossing over occurs
    –   Homologous
        chromosomes line up
        next to each other and
        can switch ends
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II
Results of Meiosis

   4 haploid cells
   Spermatogenesis – creation of 4 sperm cells
   Oogenesis – creation of 4 “egg” cells but only
    1 becomes egg cell
   meiosis...
Meiosis versus Mitosis

								
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