Topic 6. PLANT REPRODUCTION
- replication and perpetuation of organelles, cells, organisms, and species a fundamental property of lifea. Asexual ReproductionTwo phases of reproduction
b. Sexual
Reproduction
-Gametic cell division (meiosis)
-Results in segregation of genetic traits
DNA-----------› RNA-------------› Protein (enzyme)
Gene - a unit of heredity; a sequence of DNA nucleotides that codes for a
protein
Chromosome - a thread-like body made up of DNA and chromatin
2. Sites of occurrence
DNA replication
.......nucleus
RNA synthesis..........nucleus
Protein synthesis.......cytoplasm
(ribosomes)
3. Codons
- the basic
unit of genetic information
- 3 bases/codon
or an amino acid
- i.e. AAG = lysine GAG = asparagine
2N ----------------Mitosis----------------› 2N + 2N
(diploid) ; (diploid) (diploid)
2. Meiosis
- Cell division leading to gamete formation
- Results in a reduction of chromosome number
- Involves 2 separate divisions
3. Chromosome Numbers1st division 2nd division.
2N ------------------meiosis-------------------› N + N + N + N
(diploid) (gametes, haploid)2N = 20X = 10
where N = gametic number of chromosomes
X = ploidy number
N number refers to halfness (gametic number)
X number refers to oneness (genomic number)
4. Ploidy2N = number of chromosomes in somatic cells (somatic chromosome number) - Chromosome number varies by species
- Genomic (X) number is a set of different chromosomes
N = number of chromosomes in gametic cells (gametic chromosome number)
X = Number of chromosomes in a genome complement (genomic chromosome number)
a. Euploidy - variation between chromosome sets
4X---------------meiosis----------------›
2X + 2X
(tetraploid) &nb
sp; (diploid gametes)
Ploidy | Somatic | Gametic |
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Example: Chromosome numbers of some horticultural crops
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(2N) |
(N) |
(X) |
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How to To Make a Polyploids
Colchicine (chromosome doubling)
Diploid Plant (2X) --------------------------------------------› Tetraploid plant (4X)
Germinating seed,
or meristem
Colchicine treatment:
Aneuploidy |
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Trisomic | 2N + 1 (extra) | 11 22 33 44 55 66 777 |
Monosomic | 2N - (deficient) | 11 22 3_ 44 55 66 77 |
Double-trisomic | 2N + 1 + 1 (2 extra) | 11 22 33 44 555 66 77 |
4 of o chromosome | 2N + 2 (2 extra) | 11 22 33 44 5555 66 77 |
Note:
Down syndrome in humans - caused
by a trisomic for chromosome # 21
(three
chromosomes instead of two)
- Alternation of sporophytic (2N) and gametophytic
(N) stages in cycles.
- In plants, the gametophytic stage is brief.
a. Microgametophyte - pollen or male gametophyte
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- One tube nucleus
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Megagametophyte
1 egg nucleus
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A process of fertilization in which one male gamete (sperm nucleus, 1N) unites the egg nucleus (1N) to form embryo (zygote, 2N) and the other sperm nucleus unites polar nuclei (2n) to form endosperm (3N).
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