Meiosis Notes Sheet
I.
Mitosis vs. Meiosis
MEIOSIS-Cell division to produce egg and sperm cell
MITOSIS
MEOSIS
Cell Division
Cell Division
46 chromosomes2 cells that have
46 chromosomes each
46 chromosomes4 cells with 23
chromosomes each
# of chromosomes remain the same
# of chromosomes are cut in half
Found in body cells
Found in sex cells
Most common
Least common
No genetic variation
MOST genetic variation
II. Chromosomes
Karyotype –
Display of chromosomes lined up in homologous pairs
Homologous Chromosomes1 chromosome from the male and one from the female
Body Cells/Somatic Cells= ____DIPLOID_______(2N)
Sex Cells/Sperm + Egg= _____HAPLOID_________(N)
Fertilization:
When haploid sperm and egg meet, containing N chromosomes with N
chromosomes=2N
Zygote-The first cell of the baby. It is a fertilized egg
EGG=23
Sperm Cell=23
Zygote=46
Egg (23) + Sperm (23)=Zygote (46)
Chromosome Questions
Drosophilia (fruit fly) have a diploid number of 8. What is the haploid? 4
Onions have a haploid number of 8. What is the 2N?
16
A horse’s 2N is 64. What is the 1N? 32
A body cell of an alligator has 32 chromosomes. Is this the diploid or haploid
number? Diploid (2N)
II. Meiosis- cell division to produce egg (ovule) or sperm (pollen)
OogenesisFemale meiosis in the ovaries
Female meiosis in the ovaries
SpermatogenesisMale meiosis in the testis
Male meiosis in testes
Resulting cells:
End up with 4 equal sized sperm
1 egg, 3 polar bodies
One of the four cells is larger than the
other three
Eggs stop producing at a certain point
(Menopause)
Resulting cells
Resulting Cells
1 egg and 3 polar bodies
4 haploid sperm cells
Egg is used to make babies
Males can produce sperm from puberty to
the end of their life
Polar bodies get reabsorbed back into the
body
Haploid
MEIOSIS I (PMAT I &C)
Prophase I: homologous chromosomes meet up
and form tetrads. Crossing over occurs.
What is the point of crossing over?
Exchange DNA so that there is more genetic variation even more
Or to shuffle genetic variety
MEIOSIS II (PMAT II & C)
What if Meiosis did not occur?
If Meiosis DID NOT occur than individuals could NOT make off-spring.
If Meiosis did not occur, you would be genetic clone of a parent