Page 1
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
Page 2
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
Page 3
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
Page 4
An Example of Meiosis
Page 5
Chromosome Numbers
Terminology
x = Number of chromosomes in a genome Genomic chromosome number
A set of different chromosomes“Oneness”
n = Number of chromosomes in gametesGametic chromosome number“Halfness”
2n = Number of chromosomes in somatic cells
Somatic chromosome number“Wholeness”
Page 6
Fertility in Polyploid (Euploidy) Plants
Ploidy Somatic Gametic Fertility
Monoploid 2n=1x n = ? Very low
Diploid 2n=2x n = x High
Triploid 2n=3x n = ? Very low
Tetraploid 2n=4x n = 2x Variable
Pentaploid 2n=5x n = ? Variable
Hexaploid 2n=6x n = 3x Variable
Heptaploid 2n=7x n = ? Variable
Octoploid 2n=8x n = 4x Variable
Nonaploid 2n=9x n = ? Variable
Decaploid 2n=10x n = 5x Variable
Page 7
Polyploidization• Use of Cholchicine to induce polyploids
• Colchicine interferes with spindle fiber function during metaphase of meiosis
Page 8
Production of Seedless Watermelon
www.parkseed.com
Page 9
Example of Ploidy Variation
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
Page 10
Polyploidy Terminology (continued)
• EuploidyVariation between chromosome sets
• AneuploidyVariation within a chromosome set
• AutoploidyMultiplication of the complete set of
genomes of a species• Alloploidy
Polyploid containing genetically different sets of chromosomes derived from 2 or more species
Page 11
Aneuploidy Variation within a chromosome set
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
A diploid plant (2n=2x=14) would contain the following chromosome numbers depending on aneuploidy conditions:
Page 12
Life Cycle• Alternation of gametophytic (n) and sporophytic (2n) stages in a cycle
• Sporophytic (2n) stage is long and gametophytic (n) stage is brief
Page 13
Pollen Tetrad and Microgametophyte
- One tube nucleus - Two sperm nuclei
Page 14
Megagametophyte
1 egg nucleus 2 polar nuclei 3 antipodal nuclei 2 synergids
Page 15
Pollination and Fertilization, Angiosperms
Page 16
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)
Page 17
Female (left) and Male (right) Flowers of Pumpkin
Page 18
Confectionery Seed Pumpkin Production Near Hatton, ND
Honeybees
Page 19
A Hermaphroditic Flower of Peony
Page 20
Lady Slipper Orchid
Page 21
Chasmogamous Flowers of Salpiglossis
Page 23
Red, Delute Flower (RRdd)
Page 27
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
Page 29
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
Page 30
P1 P2
x
Dilute Red (RRdd)
Solid yellow (rrDD)
Solid Red (RrDd)
F1
Solid red (R-D-) 9
Dilute red (R-dd) 3
Solid yellow (rrD-) 3
Dilute yellow (rrdd) 1
F2
Page 31
RRDD or R-D- (red, solid)
RRdd or R-dd (red, dilute)
rrDD or rrD- (yellow, solid)
rrdd (yellow, dilute)