DIFFERENCES between MITOSIS & MEIOSIS

1. Mitosis is cell division of non-reproductive eukaryotic cells. Daughter cells are identical to parent cell. Parent= 2n, then daughter =2n. If parent =1n then daughter = 1n. Mitosis maintains the ploidy of the parent.

2. Meiosis is cell division of reproductive cells (gametes- eggs and sperm) where meiosis reduces the parent ploidy by half in the daughter cell. Parent = 2n, then daughter cell = 1n.

3. In meiosis there are two successive nuclear and cell divisions, with the potential to yield a total of four cells. Meiosis I is reduction- reduces ploidy level from 2n (homologous pair) to n ( ½ homologous pair), while Meiosis II is division- dividing the remainig set of chromosomes in a mitosis-like process.

4. DNA and other chromosomal components are duplicated only once, during the Interphase preceding the first meiotic division.

5. In meiosis, the homologous chromosomes containing genetic information from both parents are thoroughly shuffled and one of each pair is randomly distributed to each new cell. This gives genetic variability.

QUESTION	MITOSIS	MEIOSIS
What lines up at Metaphase I	Individual chromosomes	Chromosome pairs
What happens to centromeres at Anaphase I	Centromere splits	Centromeres stay together
Does pairing and crossing over occur at prophase	No	Yes, at Prophase I only
Is there a second division	No	Yes; it is like a mitotic division
How many daughter cells?	2 (identical to parent)	4 haploid (not identical)
Ploidy of daughter cells; number of chromosomes	Diploid= 2n; 46 chromosomes	Haploid = 1n; 23 chromosomes
Are all daughter cells the same	Yes (identical) unless mutation occurs	No

EUKARYOTES- A type of cell found in many organisms including single-celled protists and multicellular fungi, plants, and animals; characterized by a membrane-bounded nucleus and other membraneous organelles; an organism composed of such cells.

GAMETES- haploid reproductive cells (ovum and sperm)

ALLELES- Alternate forms of a gene

SOMATIC CELLS- A cell that is not or will not become a gamete; the cells of the body

POLIDY- number of sets of chromosomes

1. Haploid- organisms/cells have only one set of chromosomes; abbreviated n or N; Cells that contain only one member of each homologous pair of chromosomes (haploid number = n). At fertilization, two haploid gametes fuse to form a single cell with a diploid number of chromosomes

2. Diploid- organisms with two sets of chromosomes (most animals and many

plants); abbreviated 2n or 2N; Cells that contain homologous chromosomes. The number of chromosomes in the cells is the diploid number and is equal to 2n (n is the number of homologous pairs).

3. Polyploid- organisms with more than two sets of chromosomes; Abnormal variation in the number of chromosome sets. The condition when a cell or organism has more than the customary two sets of chromosomes. This is an especially effective speciation mechanism in plants since the extra chromosomes will establish reproductive isolation with the parental population(s), an essential for speciation.

ZYGOTE- created after fertilization of a egg by a sperm

CHROMOSOME- Structures in the nucleus of a eukaryotic cell that consist of DNA molecules that contain the genes

CHROMATID- Of a duplicated chromosome, one of two DNA molecules

HOMOLOGOUS PAIR- A pair of matching chromosomes in an organism, with one being inherited from each parent.

SYNAPSIS- linking of replicated homologous chromosomes; resulting chromosomes is called a tetrad.

CHIASMA – site where two non-sister chromatids cross over

HOMOLOGOUS CHROMOSOMES - one member of the pair is obtained from the organism's maternal parent and the other from the paternal parent; found in diploid cells

BIVALENT or TETRAD- two chromosomes and four chromatids; one chromosome coming from each parent.