Post on 29-Dec-2015
Mitosis • Occurs in body
(somatic) cells
• 2n -> 2n• 46 to 46 (in Humans) • Diploid to Diploid • Goes through PMAT
once
Meiosis • Occurs in gonads to
make gametes (sex cells) sperm and egg
• 2n -> 1n
• 46 to 23 (in Humans)
• Diploid to Haploid
• Goes through PMAT twice
Spermatogenesis• How a body makes sperm cells.
• Occurs in the testes
• One 46 chromosome cell becomes four
spermatids containing 23 chromosomes.
Oogenesis• Oogenesis makes oocytes. Egg=Oocyte
• Occurs in the Ovaries. (before birth)
• One cell containing 46 chromosomes becomes four cells containing 23 chromosomes. Three of the cells called Polar Bodies die.
• One Cell Survives and becomes an oocyte.
Asexual vs. Sexual Reproduction
• Asexual reproduction is the production of an offspring from one parent.– Budding (Jellyfish, Hydras, some Plants) – Binary Fission (bacteria) – Mitosis is used (no genetic difference from
parents)
• Sexual Reproduction is the production of an offspring from two parents. – Meiosis is used ( there is genetic variation
from parents)
P 156 1-6 1. List two ways that mitosis differs from meiosis. 2. During which stage of meiosis is the diploid
number of chromosomes reduced to the haploid number of chromosomes?
3. How many chromosomes do gametes normally contain?
4. Explain the role of crossing over to ensure genetic variation.
5. Describe the primary difference between spermatogenesis and oogenesis.
6. Explain why the chromosomes in haploid cells that are produced in meiosis I look different from those produced in meiosis II