Meiosis

• Haploid gametes in the ovaries and testes in animals, and spores in plants.
• - only in sex organs
• - produces eggs
• - producing sex cells
• -produces different cells

• Haploid cells: half genetic material, one set of chromosomes, 27 chromosomes in humans
• Diploid cells: 2 sets of chromosomes, complete # of chromosome ( varies depending on species ), 46 chromosomes in humans

• Mitosis: Skin, digestive tract, hair folicle, nails etc, growth and repair, Diploid, Identical
• Meiosis: testes, ovaries, sporangium, sperms and eggs ( gametes ), haploid, genetically different

same length, centromere in same position, trait they code for is the same

" own body ", homologous chromosomes that code for your own body trait

• not homologous, not autosomal, XY, male, female
• male = XY(have 22 homologous chromosomes) female = XX ( have 23 homologous chromosomes )

results in replication of the genetic material to form chromatids, and an increase in the number of organelles, happens only once

b/c the homologous chromosomes, they are being separated, 6 to begin with and now 3

is like mitosis, chromosome # has not changed

• chromosomes form, chromatin coling
• - nuclear envelope breaks down
• - centrosomes and centrioles move to oppisite ends of the cell and form spindle fibers
• 

" coming together " process that brings homologous chromosomes together ( pair up )

" 4 " chromatids, end process(result of) of a synapsis

spindle fibers " change " the position of the tetrads so that they line up in the middle of the cell ( random )



MITOSIS : no synapsis, no tetrad, individually lined up above the other

homologous chromosomes are pulled " apart " to opposite ends of the cell by the shortening of spindle fibres.



MITOSIS: no reduction in #'s, spindle fiber shortens, centromere splits, chromatids separated, dragged to oppisite ends

• -chromatin porms
• - nuclear envelope reforms
• - spindle fibers dissapear
• - cytoplasm of the cell splits to form 2 haploid cells, each with only one set of homologous chromosomes

MITOSIS : Diploid and identical

separates the chromatids and results in four haploid gametes

MITOSIS : diploid cells, and body cells

• - mutations
• - changes in nucleotide sequence
• causes: radiation, chemicals in environment, viruses, errors in DNA replication

• -puts them into different gametes
• - different variations and shuffling them

overlap, 2 chromatids overlap

the structure that forms as a result of cross-over, overlap ( x shaped structure )

• the x shaped structure breaks and segments are exchanged, end products of cross over
• - has maternal + paternal portions to it

happens at metaphase I, random arrangement of the homologous chromosomes in the middle of cell

• 2^n -> haploid # of chromosomes
• 2^2 = 4 possible outcomes

no separation of homologous chromosome or chromatids happening in meiosis I and meiosis II

• - extra chromosome in sex cells
• - 47 chromosome instead of 46
• - happens more when women is older and has kid
• - also called trisomy 21
• SYMPTOMS
• - tongue is larger, shorter
• - body features anormal
• - eyes not round, broader
• - face round, flat face
• - fingers and toes more stubby
• - mental retardation
• - 50% never makes it after age 1, kidney, heart problems

• - caused by nondisjunction
• - individual that is XXy extra sex chromosome present
• - testes smaller
• - breast partially deveopled
• - not much facial or chest hair
• - hips larger than average