Reproductive Biology

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Reproductive Biology

• Cell Division
• Somatic cell division (Mitosis)
• Reproductive cell division (Meiosis)
• Flowering and Anthesis
• Megagametogenesis (EMC to Egg Cells)
• Microgametogenesis (PMC to Pollen Grains)
• Pollination and Fertilization
• Pollen germination on stigma
• Pollen tube growth through style tissue
• Double fertilization

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• Mitosis
• - Somatic Cell Division
• Ends up with same number of chromosomes in
  divided cells
• Divided cells are genetically identical to
  maternal cells

2N ---------? 2N 2N
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• Meiosis
• Reproductive cell division
• Undergoes 2 separate divisions
• Forms gametes
• Divided cells have a half of the chromosome
  numbers
• Ends up with genetic re-assortment by
  chromosomal translocation (cross-over)

2N ---?---? N N N N
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An Example of Meiosis
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Chromosome Numbers

• Terminology
• x Number of chromosomes in a genome
• Genomic chromosome number
• A set of different chromosomes
• Oneness
• n Number of chromosomes in gametes
• Gametic chromosome number
• Halfness
•    
• 2n Number of chromosomes in somatic cells
• Somatic chromosome number
• Wholeness

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Fertility in Polyploid (Euploidy) Plants
Ploidy Somatic Gametic Fertility
Monoploid 2n1x n ? Very low
Diploid 2n2x n x High
Triploid 2n3x n ? Very low
Tetraploid 2n4x n 2x Variable
Pentaploid 2n5x n ? Variable
Hexaploid 2n6x n 3x Variable
Heptaploid 2n7x n ? Variable
Octoploid 2n8x n 4x Variable
Nonaploid 2n9x n ? Variable
Decaploid 2n10x n 5x Variable
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• Polyploidization
• Use of Cholchicine to induce polyploids
• Colchicine interferes with spindle fiber
  function during metaphase of meiosis

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Production of Seedless Watermelon
www.parkseed.com
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Example of Ploidy Variation
Chromosome Number Chromosome Number Chromosome Number
Species Ploidy Somatic (2n) Gametic (n) Genomic (x)
Spinach 2x 12 6 6
Corn 2x 20 10 10
Potato 4x 48 24 12
Strawberry 8x 56 28 7
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Polyploidy Terminology (continued)

• Euploidy
• Variation between chromosome sets
• Aneuploidy
• Variation within a chromosome set
• Autoploidy
• Multiplication of the complete set of genomes
  of a species
• Alloploidy
• Polyploid containing genetically different sets
  of chromosomes derived from 2 or more species

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Aneuploidy Variation within a chromosome set
A diploid plant (2n2x14) would contain the
following chromosome numbers depending on
aneuploidy conditions
  Aneuploidy Somatic chromosome number  Examples
 Trisomic  2n 1 (extra) 11  22  33  44  55  66 777
 Monosomic   2n - 1 (deficient) 11 22 3_ 44 55 66 77
 Double-trisomic 2n 1 1 (2 extra) 11  22  33  44  555  66  777
4 of one chromosome 2n 2 (2 extra) 11  22  33  44  5555  66  77
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• Life Cycle
• Alternation of gametophytic (n) and sporophytic
  (2n) stages in a cycle
• Sporophytic (2n) stage is long and gametophytic
  (n) stage is brief

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Pollen Tetrad and Microgametophyte
  - One tube nucleus    - Two sperm nuclei 
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Megagametophyte

•  
• 1 egg nucleus 
• 2 polar nuclei
•   3 antipodal nuclei
•   2 synergids    

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Pollination and Fertilization, Angiosperms
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Double Fertilization
A process of fertilization in which one male
gamete (sperm nucleus, n) unites the egg nucleus
(n) to form embryo (zygote, 2n) and the other
sperm nucleus (n) unites polar nuclei (2n) to
form endosperm (3n)
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Female (left) and Male (right) Flowers of Pumpkin
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Confectionery Seed Pumpkin Production Near
Hatton, ND
Honeybees
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A Hermaphroditic Flower of Peony
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Lady Slipper Orchid
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Chasmogamous Flowers of Salpiglossis
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Red, Delute Flower (RRdd)
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Floral Parts
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Influence of Pollination on Seed SetSalpiglossis
sinuata
No. tetrads placed Capsules setting seed () Avg. no. of seeds per capsule Avg. no. of seeds per tetrad
0 0 0 0
1 0 0 0
2 0 0 0
3 9.1 0.2 3.0
4 9.1 0.3 2.0
5 46.2 0.9 1.8
6 50.0 0.9 1.8
7 54.5 1.1 1.3
8 72.7 1.5 2.1
9 81.8 1.5 2.0
10 90.9 2.4 2.7
15 91.7 2.3 2.5
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2. Hybridization
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Inheritance of Flower Colorin Velvet
Flower(Salpiglossis sinuata)

• RR or R- Red flower color
• rr Yellow flower color
• DD or D- Solid color pattern
• dd Dilute color pattern

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P1
P2
x
Dilute Red (RRdd)
Solid yellow (rrDD)
F1
Solid Red (RrDd)

F2
Solid red (R-D-) 9
Dilute red (R-dd) 3
Solid yellow (rrD-) 3
Dilute yellow (rrdd) 1
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RRDD or R-D- (red, solid)
RRdd or R-dd (red, dilute)
rrDD or rrD- (yellow, solid)
rrdd (yellow, dilute)
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