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THE CELLULAR BASIS OF REPRODUCTION AND DEVELOPMENT

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					THE CELLULAR BASIS OF
 REPRODUCTION AND
    DEVELOPMENT
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• “LIKE BEGETS LIKE…MORE OR LESS”
• ASEXUAL REPRODUCTION VS. SEXUAL
  REPRODUCTION
  – ASEXUAL  DEFINITION?
  – SEXUAL  DEFINITION?
    • HOW DO OFFSPRING OF PARENTS FROM SEXUAL
      REPRODUCTION COMPARE TO THEIR PARENTS? EACH
      OTHER? NON-RELATED ORGANISMS?
• CHROMOSOMES
  – DEFINITION??
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• CELLS ARISE ONLY FROM PRE-EXISTING CELLS
• THE PERPETUATION (CONTINUATION) OF LIFE,
  IN ALL ITS ASPECTS RELIES ON THE PRINCIPLES
  OF CELLULAR REPRODUCTION
• CELL DIVISION = CELLULAR REPRODUCTION
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• CELL DIVISION PLAYS THREE MAJOR ROLES
  – 1) ??
  – 2) ??
  – 3) ??
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• PROKARYOTES REPRODUCE BY BINARY
  FISSION
  – MOST PROKARYOTES
    HAVE A SINGLE, CIRCULAR
    CHROMOSOME
  – EVEN COPYING A SINGLE
    CIRCULAR CHROMOSOME
    CAN BE EXTREMELY
    DIFFICULT
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• THE LARGE, COMPLEX
  CHROMOSOMES OF
  EUKARYOTES
  DUPLICATE WITH
  EACH CELL DIVISION
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CHROMOSOMES ARE ONLY VISIBLE DURING
  ACTIVE CELL DIVISION
• CHROMOSOME  ??
• CHROMATIN  ??
• SISTER CHROMATIDS  ??
• CENTROMERE  ??
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• THE CELL CYCLE MULTIPLIES CELLS
  – CELLS DIVIDE TO (OTHER THAN REPRODUCE)
     • GROWTH AND DEVELOPMENT
     • REPLACE LOST/DEAD CELLS
  – CELL CYCLE
     • AN ORDERLY SEQUENCE OF EVENTS THAT EXTENDS
       FROM THE TIME A CELL DIVIDES TO FORM 2 DAUGHTER
       CELLS TO THE TIME THESE DAUGHTER CELLS DIVIDE
       AGAIN
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• INTERPHASE  ??
  – G1
  –S
  – G2
• MITOTIC PHASE (CELL DIVISION)  ??
  – MITOSIS
  – CYTOKINESIS
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• CELL DIVISION IS A CONTINUUM OF DYNAMIC
  CHANGES
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• MITOSIS IS BROKEN UP INTO 4 MAIN STAGES
  – PROPHASE
  – METAPHASE
  – ANAPHASE
  – TELOPHASE
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• SPECIAL STRUCTURES THAT ASSIST MITOSIS
  – MITOTIC SPINDLE
  – CENTROSOMES (2 CENTRIOLES)
    • ONLY IN ANIMAL CELLS!!!
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• CYTOKINESIS
  – DIVISION OF THE CELL MEMBRANE TO FORM TWO
    DISTINCT CELLS
  – DIFFERS
    BETWEEN
    PLANT AND
    ANIMAL CELLS
  – WHY??
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• CLEAVAGE VS CELL PLATE FORMATION
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• DO YOU THINK IT IS GOOD FOR CELLS TO
  CONSTANTLY BE DIVIDING?
  – ANCHORAGE, CELL DENSITY,
     AND CHEMICAL
    GROWTH FACTORS
    IMPACT CELL DIVISION
    • ANCHORAGE  ??
    • DENSITY-DEPENDENCE  ??
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• GROWTH FACTORS
  – PROTEIN SECRETED BY
    A CELL THAT
    STIMULATES CELL
    DIVISION IN NEARBY
    CELLS
  – IMPACT THE CELL CYCLE
    CONTROL SYSTEM
  – THIS PARTICULAR ASPECT OF BIOLOGY IS BEING
    CLOSELY STUDIED TO BETTER UNDERSTAND CANCER!!
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CANCER
  – DEFINITION  ??
  – TUMOR  ??
  – BENIGN VS MALIGNANT
  – METASTASIS
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• FOUR CATEGORIES OF CANCER
  – CARCINOMA
  – SARCOMA
  – LEUKEMIA
  – LYMPHOMA
• TWO MAJOR TYPES OF TREATMENT
  – CHEMOTHERAPY
  – RADIATION THERAPY
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• REVIEW
  – ROLE OF MITOTIC CELL DIVISION
    • 1)
    • 2)
    • 3)
  – REMEMBER, MITOTIC CELL DIVISION RESULTS IN
    THE SAME NUMBER AND TYPES OF
    CHROMOSOMES IN THE DAUGHTER CELLS!!!
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• BEFORE WE CAN DISCUSS SEXUAL
  REPRODUCTION, WE NEED TO UNDERSTAND A
  BIT MORE ABOUT CHROMOSOMES…
• ORGANISMS TYPICALLY HAVE TWO GENERIC
  TYPES OF CELLS
  – SOMATIC CELLS
  – SEX CELLS (GAMETES)
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• SOMATIC CELLS CONTAIN HOMOLOGOUS
  PAIRS OF CHROMOSOMES
  – HOMOLOGOUS CHROMOSOMES  ??
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• TWO GENERAL TYPES OF CHROMOSOMES
  – AUTOSOMES
  – SEX CHROMOSOMES
• WHAT IS A “LOCUS”?
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• SEX CELLS (GAMETES) TYPICALLY ONLY HAVE A
  SINGLE SET OF CHROMOSOMES (LACK
  HOMOLOGOUS PAIRS)
  – WHY IS THIS IMPORTANT?? (WHAT HAPPENS IN
    SEXUAL REPRODUCTION??)
• TERMS RELATED TO CHROMOSOMES NUMBER
  – DIPLOID
  – HAPLOID
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• WHAT IS FERTILIZATION?
  – DEFINITION
• WHAT IS A ZYGOTE?
  – DEFINITION
• IF YOU ARE FROM THE FUSION OF TWO
  HAPLOID CELLS, HOW DO YOU CREATE A
  HAPLOID CELL? CAN YOU USE MITOTIC CELL
  DIVISION FOR THIS?
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• MEIOSIS
  – OCCURS ONLY IN REPRODUCTIVE
    ORGANS; A SPECIAL TYPE OF CELL
    DIVISION TO GIVE RISE TO SEX
    CELLS (GAMETES) WITH THE
    HAPLOID NUMBER OF
    CHROMOSOMES
  – REDUCES THE CHROMOSOME
    NUMBER FROM DIPLOID TO
    HAPLOID
  – RESEMBLES MITOSIS, BUT THERE ARE
    KEY DIFFERENCES
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• MEIOSIS
  – CELLS UNDERGO TWO
    CONSECUTIVE DIVISIONS
    (MEIOSIS I AND MEIOSIS II)
  – THE DIVISIONS ARE PRECEDED BY
    ONLY ONE DUPLICATION OF
    DNA(S PHASE)
  – FOUR DAUGHTER CELLS RESULT
  – EACH DAUGHTER CELL IS HAPLOID
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• MEIOSIS I
  – THE ACTUAL HALVING OF CHROMOSOME
    NUMBER OCCURS IN THIS STAGE
  – ALL THE “STUFF” THAT IS DIFFERENT TAKES PLACE
    IN THIS STAGE
  – THE GOAL OF MEIOSIS I IS TO SEPARATE THE
    HOMOLOGOUS CHROMOSOMES
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• STAGES OF MEIOSIS I
  – PROPHASE I
  – METAPHASE I
  – ANAPHASE I
  – TELOPHASE I
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• MEIOSIS II
  – CLOSELY RESEMBLES MITOSIS (BUT IS OCCURING
    WITH A HAPLOID NUMBER OF CHROMOSOMES)
  – THE GOAL OF MEIOSIS II IS TO SEPARATE THE
    SISTER CHROMATIDS
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• STAGES OF MEIOSIS II
  – PROPHASE II
  – METAPHASE II
  – ANAPHASE II
  – TELOPHASE II
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• A COMPARISON OF MITOSIS AND MEIOSIS
       MITOSIS          MEIOSIS
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• WHAT ADVANTAGE IS THEIR TO UTILIZING
  SEXUAL REPRODUCTION INSTEAD OF ASEXUAL
  REPRODUCTION?
  – POSSIBLE ANSWERS…
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• SEXUAL REPRODUCTION OFFERS AN
  OPPORTUNITY FOR VARIATION IN GENETIC
  MAKEUP (TRAITS POSSESSED BY AN
  ORGANISM)
• INDEPENDENT ORIENTATION OF
  CHROMOSOMES, CROSSING OVER, RANDOM
  FERTILIZATION, AND MUTATION ALL ALLOW
  FOR VARIATION
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• INDEPENDENT ORIENTATION OF
  CHROMOSOMES
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• INDEPENDENT ORIENTATION
  – THE ORIENTATION OF THE HOMOLOGOUS PAIRS
    OF CHROMOSOMES (TETRADS) IN METAPHASE I
    OF MEIOSIS IS BY RANDOM CHANCE
  – THE TOTAL NUMBER OF POSSIBLE COMBINATIONS
    FOR CHROMOSOMES PACKAGED IN INDIVIDUAL
    GAMETES WILL ALWAYS BE 2N WHERE
    N = THE HAPLOID NUMBER OF CHROMOSOMES
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• HOW DOES THIS INDEPENDENT ORIENTATION
  LEAD TO VARIATION?
  – HOMOLOGOUS CHROMOSOMES CARRY
    DIFFERENT VERSIONS OF A TRAIT (GENE) AT THE
    SAME LOCI; SO…
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CROSSING-OVER FURTHER ENHANCES
  GENETIC VARIATION
  – CROSSING-OVER
    • THE EXCHANGE OF
      CORRESPONDING SEGMENTS
      BETWEEN TWO HOMOLOGOUS
      CHROMOSOMES
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CROSSING-OVER
  – CHIASMA  A PLACE WHERE TWO
    HOMOLOGOUS (NON-SISTER) CHROMATIDS ARE
    ATTACHED TO EACH OTHER
  – CROSSING OVER TAKES PLACE DURING SYNAPSIS
    AND ADDS TO GENETIC VARIABILITY
• GENETIC RECOMBINATION
  – THE PRODUCTION OF GENE COMBINATIONS
    DIFFERENT FROM THOSE CARRIED BY THE
    ORIGINAL CHROMOSOMES
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CROSSING-OVER
  – STEPS IN CROSSING OVER
    1. SYNAPSIS OF TETRAD
    2. BREAKAGE OF HOMOLOGOUS CHROMATIDS
    3. JOINING OF HOMOLOGOUS CHROMATIDS
    4. SEPARATATION OF HOMOLOGOUS CHROMOSOMES
       AT ANAPHASE I
    5. SEPARATION OF CHROMATIDS AT ANAPHASE II AND
       COMPLETION OF MEIOSIS
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• ACCIDENTS DURING MEIOSIS CAN ALTER
  CHROMOSOME NUMBER
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• ACCIDENTS DURING MEIOSIS CAN ALTER
  CHROMOSOME NUMBER
  – NONDISJUNCTION –
    THE FAILURE OF
    CHROMOSOMAL PAIRS
    TO SEPARATE
  – CAN HAPPEN IN EITHER
    MEIOSIS I OR MEIOSIS II
  – MORE SERIOUS IN
    MEIOSIS I; WHY??
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CHROMOSOMAL ABNORMALITIES
  – TRISOMY 21 (MOST COMMON – 1 OUT OF 700)
    • COMMON NAME = DOWN’S SYNDROME
  – MOST INCORRECT
    CHROMOSOME NUMBERS WILL
    ABORT
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CHROMOSOMAL ABNORMALITIES
 Sex chromosomes         Syndrome                  Origin of            Frequency in Population
                                                 Nondisjunction


      XXY            Klinefelter syndrome     Meiosis in egg or sperm          1 / 2,000
                             (male)                  formation


      XYY            None (normal male)          Meiosis in sperm              1 / 2,000
                                                    formation


      XXX                Metafemale           Meiosis in egg or sperm          1 / 1,000
                                                     formation


       XO          Turner syndrome (female)   Meiosis in egg or sperm          1 / 5,000
                                                     formation
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• HOW CAN WE DIAGNOSE CHROMOSOMAL
  ABNORMAILITES?
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• WE USE KARYOTYPES
  – KARYOTYPE  AN ORDERLY DISPLAY OF
    MAGNIFIED IMAGES OF AN INDIVIDUALS
    CHROMOSOMES
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CHROMOSOMAL ABNORMALITIES
  – THESE ARE NOT JUST LIMITED TO CHROMOSOME
    NUMBER
  – EVEN WHEN THE TOTAL NUMBER OF
    CHROMOSOMES IS CORRECT, ALTERATIONS IN THE
    STRUCTURE OF CHROMOSOMES CAN STILL
    OCCUR/EXIST
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
• CHROMOSOMAL ABNORMALITIES
  – THERE ARE FOUR MAJOR TYPES OF CHANGES
    THAT CAN OCCUR
    •   DELETION
    •   DUPLICATION
    •   INVERSION
    •   TRANSLOCATION
     THE CELLULAR BASIS OF
REPRODUCTION AND DEVELOPMENT
      THE CELLULAR BASIS OF
 REPRODUCTION AND DEVELOPMENT
• WE HAVE EXPLAINED HOW CELLS DIVIDE, BUT
  WE HAVEN’T ADDRESSED WHY CERTAIN
  TRAITS APPEAR IN OFFSPRING OF SUCCESSIVE
  GENERATIONS
• COME BACK TO
  FIND OUT THE
  FULL STORY!!!

				
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