MITOSIS AND MEIOSIS

process by which a parent cell is divided into two or more daughter cells

cell division

cell nucleus divides to produce two daughter nuclei containing identical sets of chromosomes to the parent cell; happens in somatic (body) cells

• no synapsis/crossing over

• 2n

• sister chromatids separates during anaphase

mitosis

stages of mitosis

• prophase

• metaphase

• anaphase

• telophase

significance of mitosis

• keep chromosome number constant

• maintains genetic stability of daughter cells

• helps in growth and development of zygote

• body’s growth and development

• helps in repair and regeneration of cells

• production of genetically similar offspring (binary fission)

cell divides into four daughter cells, each with half the number of chromosomes of the parent cell; gametes/reproductive cells

• has synapsis/crossing over

• n

• in anaphase 1 → homologous chromosome separates

• in anaphase 2 → sister chromatids separates

meiosis

significance of meiosis

• critical for sexual reproduction

• genetic variation by way of the process of recombination

phases of meiosis

• prophase I

• metaphase I

• anaphase I

• telophase I

• prophase II

• metaphase II

• anaphase II

• telophase II

structures made from DNA sequences and proteins found at the ends of chromosomes

telomere

centromere

constricted region of a chromosome

chromosome

organized package of DNA in the Nucleus

chromatids

two identical halves of a chromosome that has been replicated in preparation for cell division

centrosome

small organelle found in eukaryotic cells, which functions as a microtubule-organizing center

spindle fibers

microtubules that separates the chromosomes into two daughter cells

centrioles

cylindrical organelles found in eukaryotic cells that are involved in the organization of cell division; help in formation of spindle fibers that separates chromosomes

diploid cells

have pairs of chromosomes; in the body cells of most organisms, chromosomes occur in pairs.

haploid cells

have only one chromosome from each pair; sex cells have only one chromosome from each pair of chromosomes

this happens in what stage of mitotic phase?

1. nucleolus disappears

2. nuclear membrane breaks apart

3. chromosomes become visible

4. spindle apparatus forms and attaches to centromeres of chromosomes

prophase

this happens in what stage of mitotic phase?

1. nuclear membrane is completely gone

2. duplicated chromosomes line up along equatorial plane

metaphase

kinetochore

protein complex assembled on the centromeric region of DNA → provides the major attachment point for the spindle microtubules

this happens in what stage of mitotic phase?

1. diploid sets of daughter chromosomes separate

1. they are pushed and pulled toward opposite poles of the cell by the spindle fibers

anaphase

this happens in what stage of mitotic phase?

1. nuclear membrane and nucleoli (nucleus) reform

2. cytokinesis is nearly complete

3. cell plate begins to form

4. cell prepares for final division

telophase

cytokinesis

final stage of Mitosis → cytoplasm, organelles, and nuclear material are evenly split and two new cells are formed

normal number of chromosomes

46