Download 10.2 Meiosis


Cross TT X Tt

Give the genotypic and phenotypic ratios

Male - spermatogenesis
Occurs frequently
 Produce sperm cells


Female - Oogenesis
Occurs every 28 days
 Produce one egg

Do not copy



One mother cell produces four daughter
cells
Each daughter cell has haploid
chromosome # (1/2 of what mother had)
Occurs in sex cells (sperm and egg)






1. Interphase - mature cell ready for cell
division
2. Prophase I - chromosomes are short, thick
and double attached by centromere
3. Metaphase I - tetrads align at equator
4. Anaphase I - Tetrads split and move to
opposite poles
5. Telophase I - events occur in the reverse of
prophase I
Don’t copy




6. Metaphase II - chromatids align at equator
7. Anaphase II - chromatids split and move to
opposite poles
8. Telophase II - 4 cells with haploid #(new
sperm and egg cells)
Don’t Copy
http://www.cellsalive.com/meiosis.htm

Mitosis
Asexual and sexual
 Identical cells
produced
 Same
#chromosomes (46)
 Body cells
 One Division
 Two cells made
 20 minutes to one
hour


Meiosis







Sexual cell division
Cells different
Different number of
chromosomes (23)
Sex cells
Two divisions
4 cells made
Occurs in days


Crossing Over
Genetic Recombination




Trisomy - extra chromosome (down syndrome)
Monosomy - lacking a chromosome (most
lethal, Turner Syndrome)
Triploidy - three sets of chromosomes
Polyploidy - more than the usual number of
chromosomes (rare in animals, common in
plants)




Gene - portion of DNA that is genetically
active, controls traits
Chromosome - Thread like, humans 23 pairs
Haploid chromosome # (n) - single set of
chromosomes
Diploid chromosome # (2n) - two of each kind
in a cell



Homologous Chromosome - same
Allele - one-half of a gene pair (T or t)
Gamete - Sex cell, reproductive cell



Sperm - male haploid # (Father) 23
chromosomes
Egg - female haploid # (Mother) 23 chromosomes
Zygote - fertilized egg by a sperm, diploid
number (2n) = 46 chromosomes, 23 pairs
•Organized photo
of a person’s
chromosome
•Autosomes vs. sex
chromosomes