Meiosis Notes

Vocab…

· Cell cycle: Interphase (G1, S, G2), mitosis (cell division) and cytokinesis (pinching off into two cells)

· Mitosis- division of cells producing 2 IDENTICAL cells (somatic or autosome cells – skin, heart, liver)

· _______________________- sperm and egg

· _______________________- fertilized egg cell

· _______________________- half chromosomes (23)

· _______________________- all chromosomes (46)

· _______________________- 2 chromatids (strands) and centromere (center)

Mitosis Review….

· Prophase- start to divide, Let’s DO THIS!

· Metaphase- line up in middle

· Anaphase- centromeres break apart (form a’s)

· Telophase- everything is identical on both ends and starts to form into two

· Cytokinesis- final pinching off of 2 identical cells

· ** remember mitosis produces identical cells, so each parent cell has 46 chromosomes, baby has 46 chromosomes***

A ______________________

B ______________________

C ______________________

D ______________________

E ______________________

Meiosis

· Meiosis- division of ____________ cells (sperm and egg)

· Produces __________________________ with half the number of chromosomes so when baby forms he/she has half from mom and half from dad

Meiosis Process

· Involves ____ divisions: meiosis 1 and meiosis 2 (each broken into PMAT)

· Starts with homologous pairs that DO NOT break apart until meiosis 2

· Results in _____ haploid cells, each having ___________ the number of chromosomes (zygote- half from mom and half from dad)

Meiosis contributes to ______________________________________________________

1) ______________________________________- random homologous chromosomes

2) _________________________________ - Prophase 1- occurs (portion of one

chromosome switches onto another, producing diversity)

3) ________________________________________ - The sperm that fertilizes the egg is simply by chance

Importance of Genetic Variation

· Meiosis is essential to ___________________________ - No genetic process generates variation more readily

· Pass on learned traits

· Creates ________________________

Meiosis results in gametogenesis

· Gametogenesis- formation of gametes

Spermatogenesis- formation of ____________________________

· Diploid cell increases in size and shape and becomes a large immature cell called a _______________________

· Cell undergoes meiosis 1 resulting in 2 cells

· 2 cells undergo meiosis 2 forming 4 haploid cells

· ALL 4 of the haploid cells grow a tail and become sperm

· Each sperm is genetically different

· Sperm is produced throughout a man’s reproductive years

Oogenesis- forming ________________________________

· During meiosis 1 the cytoplasm divides unevenly, one cell gets most of the cytoplasm and this will become the ______________

· Larger cell undergoes meiosis 2, division is uneven again, the larger cell becomes an ______________

· Ovum - egg ready for fertilization

· Other cells produced become _______________ bodies- cells that just get reabsorbed into the human body

· Egg development begins before birth, during embryonic development cells divide by mitosis to produce 2 million immature egg cells

· Ovaries of a newborn contain all the eggs a female will ever have

· During puberty egg cells complete meiosis 1

· Once egg is fertilized, egg undergo meiosis 2

Reproduction

Two types:

1) _______________________ reproduction - _____ parent

a. produces clones

b. prokaroytes (bacteria) - binary fission

c. eukaryotes

- fragmentation (planaria) body breaks into two pieces and develop

- budding (hydra) new offspring splits from existing one

2) ______________________ Reproduction -

- _________ parents forming haploid gametes combine to form a fertilized egg (zygote)

- offspring has a combination of traits from mom and dad

Sexual versus Asexual

Asexual ReproductionSexual Reproduction

Pro Pro

- produce many organisms in a short time - different combination of genes, able to adapt

Con Con

- no variation, can NOT adapt- long period of time

1. How many cells does mitosis produce?

2. How many cells does meiosis produce?

3. Identical cells are produced by which process?

4. Genetically different cells are produced by which process?

5. What kind of cells does meiosis produce?

6. What kind of cells does meiosis produce?

7. Asexual organisms use which process to reproduce?

8. Sexual-reproducing organisms use which process to reproduce?