Meiosis and Alternation of Generations Flashcards
Production of cells identical in chromosomes with cells from which they arose
Asexual reproduction
Production in nearly all plants
Sexual reproduction
Number of chromosomes reduced to half
Division I (Meiosis I or Reduction Division)
No further reduction in chromosome number
Division II (Meiosis II or Equational Division)
Chromosomes coil and condense, and are in homologous pairs. Nuclear envelope and nucleolus
disassociate
Prophase I
Each closely associated pair of chromosomes exchange parts
crossing-over
Chiasmata form where arms of chromosomes touch. Results in exchange of DNA by two parents
Crossing Over in Prophase l
Chromosomes align in pairs at equator. Spindle formation completed.
Metaphase l
One whole chromosome from each pair migrates to a pole
Anaphase
Original cell becomes two cells or two nuclei
Telophase I
Chromosomes become shorter and thicker
Prophase II
Centromeres become aligned along equator. New spindles completed.
Metaphase II
Centromeres and chromatids of each chromosome separate, and migrate to opposite poles
Anaphase II
Coils of chromatids relax and chromosomes become longer and thinner. Nuclear envelope and nucleoli reappear for each group of chromosomes. New cell walls form
Telophase II
Cell with one set of chromosomes — gametes
Haploid
Cell with two sets of chromosomes — zygote
Diploid
Cell with more than two sets of chromosomes
Polyploid
Three sets of chromosomes
Triploid
Six sets of chromosomes
Hexaploid
8 sets of chromosomes
Octaploid
Life cycle involving sexual reproduction that alternates between diploid sporophyte phase and haploid gametophyte phase
Alternation of generations
develop from zygotes and produce sporocytes
Sporophytes
undergoes meiosis and produces 4 haploid spores
Sporocyte
develop from spores. Form cells or sexual structures in which gametes are formed by mitosis
Gametophytes
Fertilization produces ?
zygote
Fusion of gametes
Fertilization
