1. Houston…We have a problem…
Non-disjunction: Cell division in which the sister chromatids do NOT separate correctly, resulting in gametes with an abnormal number of chromosomes.
This is how Down Syndrome happens…the chromosomes don’t separate correctly, and too many end up in the gamete.
People with Down Syndrome have 47 chromosomes instead of ____.
These are correct!
No problem
Notice there are NO chromosomes in these cells!
Notice that non-disjunction occurred here too! 46

2. Click on Link for animation…
Meiosis Overview

3. Compare & Contrast Mitosis & Meiosis
Page 34 in Comp Book
Compare & Contrast Mitosis & Meiosis
Mitosis
Meiosis
* Occurs in body cells
Both
* Occurs in gametes cells
* Divides once
* Divides twice (meiosis 1 & II
* Creation of new cells
* Creates 2 cells
* Creates 4 cells
* DNA replicates once
* Are genetically identical
* Are NOT genetically identical
* Increases genetic diversity

4. This results in gametes with abnormal numbers of chromosomes:
Clicker Question #18
This results in gametes with abnormal numbers of chromosomes:
meiosis
mitosis
non-disjunction
crossing-over

5. This is an example of non-disjunction:
Clicker Question #19
This is an example of non-disjunction:
Color blindness
Down Syndrome
Cystic fibrosis
Sickle cell anemia
Karyotypes—Identify genetic diseases

6. Answer: NO...They are using Binary Fission
Many Bacteria & protozoans do not need a partner to reproduce. Are they reproducing using mitosis?
Answer: NO...They are using Binary Fission
Binary Fission – Asexual form of reproduction used by some prokaryotes in which a cell divides into two genetically identical cells. (creates a new individual)
SIMILAR/LIKE “cloning” themselves
1 bacterium could become 1,000,000,000 (billion) in 10 hours!

7. What are the advantages & disadvantages to being asexual & sexual?
Asexual Reproduction
Advantages
Disadvantages
Can reproduce without a partner…
They don’t have to find a mate/partner.
No genetic variation…They are clones. Its putting all your eggs in one basket. If a something kills the parent, it WILL kill ALL the offspring too. Easily becomes extinct with little change to environment.
Able to reproduce quickly. The greater the number of offspring, the better the survival rate of the population.
Quick reproduction is also a disadvantage because too many individuals will be competing with each other for food & space

8. What are the advantages & disadvantages to being asexual & sexual?
Sexual Reproduction
Advantages
Disadvantages
Genetic diversity!
Has the ability to create endless recombination of genes (crossing-over) coming from 2 parents, all individuals are different in some way.
Must find a partner. Very difficult if the population is low and spread out.
Difficult to recover if the species is endangered.
The species is more able to adapt to environmental changes
Slow reproduction….takes time…
Slow population growth

9. Prokaryotes reproduce using:
Clicker Question #20
Prokaryotes reproduce using:
meiosis
mitosis
binary fission
binary fusion

10. Which of the following is an advantage of asexual reproduction
Clicker Question #21
Which of the following is an advantage of asexual reproduction
genetic diversity
the ability to reproduce quickly
the ability to adapt to new habitats
slow reproduction

11. Which of the following is an advantage of sexual reproduction
Clicker Question #22
Which of the following is an advantage of sexual reproduction
genetic diversity
the ability to reproduce quickly
the ability to reproduce many offspring
do not have to find a sexual partner

12. The End