Cell reproduction

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Cell reproduction
Chapter 9 10

• Chapter 8

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Reproduction

• D the creation of new individuals
• Organism reproduction inheritance
• Cell reproduction
• Cell division
• Replication vs division

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Types of Reproduction

• Asexual
• No exchange of genetic material
• Binary fission ex Bacteria
• Cloning ex sea anenome
• Mitosis
• Sexual
• Exchange of genetic material
• Gametes
• Meiosis

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Binary Fission

• Asexual Reproduction used by Prokaryotes

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Cell division
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Cell Theory

• All known living things are made up of cells
• The cell is the structural and functional unit of
  all living things
• All cells come from pre-existing cells by
  division
• Cells contain hereditary information which is
  passed from cell to cell during cell division
• All cells are basically the same in chemical
  composition
• All energy flow (metabolism biochemistry) of
  life occurs within cells

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Cell Division

• Replication or creation of new individual cells
• Function
• Growth
• Repair
• Maintenance
• Asynchrony

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Cell Cycle

• Life of a cell
• Divided into ordered phases based on functions
• Cell cycle phases (3)
• Interphase (3)
• Normal activities
• Replication
• Mitotic phase (4)
• Division
• Cytokinesis (1)

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Cell cycle
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Cell cycle Regulation
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Apoptosis

• Programmed cell death
• Growth development
• Protection

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Interphase

• 90 of cells life
• Normal functions DNA replication

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DNA Duplication

• Copying of genetic sequence
• Occurs when in chromatin form
• Terminology
• Chromatin
• Sister Chromatid
• Chromosome
• Daughter cells

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Existing strand
2 strands
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Chromatin

• Combination of unwound DNA strands and proteins
  (Histones)
• Normal condition (interphase)
• Replication occurs in this stage
• Not visible w/ naked eye

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Chromatin
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Chromatin is like SpaghettiWhat???
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Aha!
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Chromosome

• Vary in number
• 23 pairs (46) Human
• Dog 78
• Packaged DNA strands
• Chromatin proteins
• Characteristic of Mitotic phase
• Chromosomes come in pairs
• Diploid (2n) vs. Haploid (1n)

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Sister Chromatids

• Duplicate copies of each chromosome
• Each individual chromatid
• Share centromere
• Centromere
• D tightened region where chromatids attach to
  each other (waist)

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Centromere
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Daughter Cells

• Two new individual chromosomes after they have
  dis-attached
• Identical copies
• Each will end up in different cells
• When separate each considered an individual
  chromosome

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Chromosome duplication
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Mitosis
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Mitotic phase

• Division of cell contents
• Does not involve replication
• In eukaryotic cells
• Evolutionarily conserved
• 4 stages-Continuous process
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis

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Mitotic Spindle

• Series of microtubule fibers used to move
  chromosomes around during cell division
• Originate from opposite poles
• Collectively known as the mitotic spindle
• Works like pully system

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Mitotic spindle
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http//www.biologycorner.com/resources/mitosis-ani
mated.gif
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Prophase

• Chromatin fibers coil into sister chromatids
  (collectively a chromosome)
• DNA now visible
• Nucleoli disappears
• Nuclear envelope begins to break down
• Spindle fibers forming and attach to chromosomes
  at centromere
• Chromosomes start to migrate to centerline of cell

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Prophase
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Prometaphase
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Prophase
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Metaphase

• Mitotic spindle now fully formed
• Sister chromatids (chromosome) lined up at
  centerline
• Spindle fibers attached to each sister chromatid
  pair
• Held aligned in place by spindle tug of war

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Metaphase
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Metaphase
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Anaphase

• Sister chromatids separated by force of spindle
  fibers
• Sudden action
• Separated sister chromatids are now daughter
  cells- each a chromosome
• Chromosomes segregated to opposite poles
• Cell elongates

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Anaphase
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Anaphase
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Telophase

• Chromosomes segregated to opposite poles begin to
  uncoil back to chromatin
• Spindle microtubules break down
• Nucleoli reappears
• Nuclear envelope reforms

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Telophase
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Telophase
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Telophase
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Cytokinesis

• Division of cytoplasm
• Occurs concurrently with last stages of Mitotic
  phase
• Cleavage furrow pinches cell in two
• Result of Mitosis cytokinesis 2 daughter cells
• Slightly different in animals plants

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Cytokinesis
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Animal Mitosis
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Plant Mitosis
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Cancer

• Disruption of cell cycle control system
• Cell division timing or location of division
  affected
• Cancer types
• Carcinomas- external
• Sarcomas- bone muscle
• Leukemias Lymphomas- blood blood forming
  tissue
• Cancer cells
• Regionalized division- tumor
• Spread- metastasis

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Breast cancer cell
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Types of Reproduction

• Asexual
• No exchange of genetic material
• Binary fission ex Bacteria
• Cloning ex sea anenome
• Mitosis
• Sexual
• Exchange of genetic material
• Gamates
• Meiosis

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Reproduction
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Meiosis

• Special kind of cell division
• Occurs only in gonads
• Crucial in alternation of generation
• Segregates homologous chromosomes
• Introduces genetic variation
• 2 divisions with only 1 replication
• 4 haploid daughter cells

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Terminology

• Somatic cell vs Sex cell
• Karyotype
• Chromosome types
• Autosomal
• Sex
• Genome

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Somatic Cells vs Sex cells
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Karyotype
Autosomal Chromosomes
Sex Chromosomes
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Genome

• All the genes on all of an individuals chromosomes

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Homologous Chromosomes

• 46 chromosomes, 23 pairs
• Each pair carries different genetic information
• Pairs composed of 1 chromosome from each parent

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Homologous Chromosomes
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Alternation of Generation
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Alternation of Generation

• Sequence of stages in life from generation to
  generation
• Sexual reproduction
• Diploid- 2n
• Somatic cells
• Homologous chromosomes paired
• Haploid- 1n
• Gametes
• Ovary/testes
• Insemination
• Fertilization
• zygote

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Meiosis is critical for life cycles
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When things go awry
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Meiosis I
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Meiosis II
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Genetic Diversity

• 2 ways meiosis introduces genetic variability
• Independent assortment
• Crossing over
• Random fertilization

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Tetrad

• Homologous chromosomes attach at centromere
• Attach via synapsis

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Crossing Over

• Method of exchanging genetic material between
  homologous chromos
• Occurs during Prophase I of Meiosis I
• When areas of homologous chromosomes that form a
  gene-gene alignment
• Point of attachment Chiasma
• Results in genetic recombination that introduces
  added layer of genetic variation
• Produces hybrid chromosomes

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Independent Assortment

• The characteristic of chromosome tetrads lining
  up in random order during Metaphase I of Meiosis
  I
• Tetrads are broken during Anaphase I Homologous
  chromosomes are separated
• Results in shuffling of genetic information
• For each chromosome pair new cells receive EITHER
  mothers OR fathers chromosome
• AKA Independent assortment
• Haploid cells
• Note- pairs of sister chromatids stay together

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Independent assortment
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Errors in Meiosis

• Most errors result in natural miscarraige
• Some errors are not lethal
• Most common error Nondisjunction

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Non-disjunction

• Failure of chromosomes to separate during EITHER
  Meiosis I or II
• Result in chromosomal abnormalities
• Fertilization of gamete with non-disjunction
  results in abnormalities
• Abnormality occurs in all resulting cells
• Examples
• Trisomy 21
• Abnormal sex chromosomes

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Trisomy 21

• Aka Downs syndrome
• Non-disjunction of autosome resulting in 3
  chromosomes 21
• Relatively common- 1/700
• Characteristic results that vary in severity

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Sex Chromosomes

• Non-disjunction in sex chromosomes
• Results in abnormal numbers of sex chromosomes
• Less impact than autosomal non-disjunction
• Y is small, less genes, non-essential
• X multiple copies OK, only 1 works
• Various impacts

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Klinefelter Syndrome
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Meiosis vs Mitosis

• Meiosis 2 divisions
• Segregates homologous chromosomes
• Produces haploid daughter cells
• Introduces genetic variation crucial for
  diversity and evolution

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