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Meiosis 1. By: Shirelle Ruffin Biology Honors January 5, 2012. Meiosis is a process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell. Produces gametes (which are haploid reproductive cells.). PROPHASE 1.

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meiosis 1

Meiosis 1

By: Shirelle Ruffin

Biology Honors

January 5, 2012

slide2

Meiosis is a process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell.

Produces gametes(which are haploid reproductive cells.)

prophase 1
PROPHASE 1
  • DNA winds into chromosomes
  • Spindle fibers appear
  • Synapsis is the pairing of homologous chromosome
  • During synapsischromatids within homologous pair twist around one another.
slide4
Parts of chromatids may break off and attach to the adjacent chromatids on the homologous chromosomes called crossing over.

Crossing over permits the exchange of genetic material between maternal and paternal chromosomes.

metaphase 1
METAPHASE 1
  • Tetrads line up along the midline of the dividing cell.
  • Spindle fibers from one pole, attach to the centromere of one homologous chromosome.
  • Also spindle fibers from the opposite pole attach to the other homologous chromonsome of the pair.
anaphase 1

Contain two chromatids attached by a centromere

ANAPHASE 1
  • Each homologous chromosome moves to an opposite pole of the dividing cell.
  • The separation of homologous chromosomes is called independent assortment.

Independent Assortment is a result in genetic variation.

telophase cytokinesis 1
TELOPHASE & CYTOKINESIS 1

During telophase 1 the chromosomes reach the opposite ends of the cell and cytokinesis begins, which means the new cells contain a haploid number of chromosome.

reproductive division haploid gametes
Reproductive DivisionHaploid Gametes

Haploid cells have only one autosome of each homologous pair and only one sex chromosomes. (23 total)

Haploid cells have half the number of chromosomes that are present in diploid cells.

*When a sperm cell and egg cell combine to create the first cell of a new organism the new cell will be diploid.

reproductive division spores
REPRODUCTIVE DIVISIONSPORES
  • A spore is a haploid reproductive cell surrounded by a hard outer wall.
  • Spores allowed the widespread dispersal of plant species.
  • Nonvascular plants are the three groups of plants that lack specialized conducting tissues and true roots, stem, and leaves.
  • Vascular plants is a plant that has true roots, stem, and leaves and a vascular system composed of xylem and phloem.