Mitosis And Meiosis

1. Mitosis and MeiosisMitosis and Meiosis
By: Richard Shirk, Jr.By: Richard Shirk, Jr.

2. What Are Mitosis And What Are Mitosis And
Meiosis?Meiosis?
Both are types of reproduction used Both are types of reproduction used
during the cell cycleduring the cell cycle
 Each type of cell division are Each type of cell division are
specialized for different types of cellsspecialized for different types of cells
Both undergo the cell cycle in very Both undergo the cell cycle in very
similar, yet very different wayssimilar, yet very different ways

3. Important DefinitionsImportant Definitions
DNADNA: a molecule composed of deoxyribose : a molecule composed of deoxyribose
nucleotides and contains the genetic information of nucleotides and contains the genetic information of
living cellsliving cells
ChromosomeChromosome: a single DNA double helix together : a single DNA double helix together
with proteins that help to organize the DNAwith proteins that help to organize the DNA
ChromatidChromatid: one of the two identical strands of DNA : one of the two identical strands of DNA
and protein that forms a replicated chromosomeand protein that forms a replicated chromosome
GeneGene: a unit of heredity; specifies the amino acid : a unit of heredity; specifies the amino acid
sequence of proteins and hence particular traitssequence of proteins and hence particular traits
AlleleAllele: one of several alternative forms of a : one of several alternative forms of a
particular geneparticular gene
LocusLocus: the physical location of a gene on a : the physical location of a gene on a
chromosomechromosome

4. Important Definitions Important Definitions
(cont.)(cont.)
DiploidDiploid: referring to a cell with pairs of homologous : referring to a cell with pairs of homologous
chromosomeschromosomes
HaploidHaploid: referring to a cell that has only one : referring to a cell that has only one
member of each pair of homologous chromosomesmember of each pair of homologous chromosomes
Homologous PairHomologous Pair: two homologues that are similar : two homologues that are similar
in appearance and genetic information that pair in appearance and genetic information that pair
during meiosisduring meiosis
HeterozygousHeterozygous: carrying two different alleles of a : carrying two different alleles of a
given genegiven gene
HomozygousHomozygous: carrying two copies of the same allele : carrying two copies of the same allele
of a given geneof a given gene

5. MitosisMitosis
Mitosis is the division of chromosomes in a Mitosis is the division of chromosomes in a
cellcell
Usually followed by cytokinesis or cell Usually followed by cytokinesis or cell
divisiondivision
Daughter cells produced after mitosis have Daughter cells produced after mitosis have
same number of chromosomes as original same number of chromosomes as original
cellcell
Purpose of mitosis is replication of somatic Purpose of mitosis is replication of somatic
cells and asexual reproductioncells and asexual reproduction
Somatic cells include all cells in the body Somatic cells include all cells in the body
except the egg or spermexcept the egg or sperm

6. MeiosisMeiosis
Meiosis is the division and reduction of Meiosis is the division and reduction of
the chromosomes of a cellthe chromosomes of a cell
Daughter cells produced have half the Daughter cells produced have half the
chromosomes as the original cellchromosomes as the original cell
Purpose of meiosis is the production of Purpose of meiosis is the production of
gametes (sex cells)gametes (sex cells)

7. Stages Of The Cell CycleStages Of The Cell Cycle
InterphaseInterphase
Synthesis Synthesis
ProphaseProphase
MetaphaseMetaphase
AnaphaseAnaphase
TelophaseTelophase

8. Interphase And Synthesis Interphase And Synthesis
Stages Of Mitosis And MeosisStages Of Mitosis And Meosis
During Interphase the cell carries out During Interphase the cell carries out
normal activities such as metabolism normal activities such as metabolism
and protein synthesisand protein synthesis
During synthesis the DNA in each During synthesis the DNA in each
chromosome is replicatedchromosome is replicated

9. Prophase And Metaphase Prophase And Metaphase
Stages of MitosisStages of Mitosis
The prophase stageThe prophase stage
– chromosomes condense chromosomes condense
and would be visible and would be visible
under a light microscope under a light microscope
–the nuclear membrane the nuclear membrane
degradesdegrades
In the metaphase stage In the metaphase stage
the chromosomes line the chromosomes line
up along the equatorup along the equator

10. Anaphase And Telophase Anaphase And Telophase
Stages of Mitosis And Stages of Mitosis And
CytokinesisCytokinesis
In the anaphase stage In the anaphase stage
the sister chromatids the sister chromatids
separate and move to separate and move to
opposite ends of the opposite ends of the
cellcell
In the telophase stage In the telophase stage
one set of each one set of each
chromosome reaches chromosome reaches
each poleeach pole
Cytokinesis begins and Cytokinesis begins and
the cell divides in two the cell divides in two
creating two diploid creating two diploid
cellscells

11. Meosis IMeosis I
Prophase IProphase I
–chromosomes visiblechromosomes visible
–hHomologous pairs of hHomologous pairs of
chromosomes come chromosomes come
together to from tetradstogether to from tetrads
–crossing over occurs crossing over occurs
when a chromatid of when a chromatid of
one chromosome in a one chromosome in a
pair exchanges a pair exchanges a
segment of itself with segment of itself with
the chromatid of the the chromatid of the
other chromosome in other chromosome in
the pairthe pair

12. Meosis I (cont.)Meosis I (cont.)
Metaphase I Metaphase I
–homologous pairs line up along the equator of the homologous pairs line up along the equator of the
cellcell
Anaphase IAnaphase I
–Homologous pairs of chromosomes separate and Homologous pairs of chromosomes separate and
move to opposite poles of cellmove to opposite poles of cell
Telophase ITelophase I
–Chromosomes complete their migration to poles Chromosomes complete their migration to poles
of the cell and cytokinesis occursof the cell and cytokinesis occurs

13. Meosis IIMeosis II
No new DNA No new DNA
replication takes replication takes
placeplace
Prophase IIProphase II
–Spindle fibers re-Spindle fibers re-
form and form and
chromosome begin chromosome begin
to move to middle of to move to middle of
cellcell

14. Meosis II (cont.)Meosis II (cont.)
Metaphase II Metaphase II
–chromosomes line up along equatorchromosomes line up along equator
Anaphase II Anaphase II
–sister chromatids of each chromosome separate sister chromatids of each chromosome separate
and move to poles of cellsand move to poles of cells
Telophase II Telophase II
–the chromatids complete migration the chromatids complete migration
–nuclei reform and cytokinesis occursnuclei reform and cytokinesis occurs
Meosis produces four haploid cellsMeosis produces four haploid cells

15. Crossing Over Of MeosisCrossing Over Of Meosis
Increases the number of allelic Increases the number of allelic
combinationscombinations
Increase in different possible physical Increase in different possible physical
expressions and characteristicsexpressions and characteristics
Allows species to try varies Allows species to try varies
combinations and find the best combinations and find the best
combination that suits their combination that suits their
environmentenvironment

16. Works CitedWorks Cited
http://genetics.nbii.gov/Basic1.htmlhttp://genetics.nbii.gov/Basic1.html
http://www.biologycorner.com/bio4/notes/meiosis.phphttp://www.biologycorner.com/bio4/notes/meiosis.php
http://www2.mcdaniel.edu/Biology/PGclass/mitosis/pg3bd.htmhttp://www2.mcdaniel.edu/Biology/PGclass/mitosis/pg3bd.htm