1. Why do we look the way we do?
Genetics
Why do we look the way we do?

2. Inheritance of chromosomes
Egg + sperm  zygote
egg
zygote
sperm

3. How does this work?
Paired chromosomes have ___________________
but __________________________
eye color
(blue?)
eye color
(brown?)
hair color

4. What did we show here?
Genes come in “versions”
brown vs. blue eye color
___________________
Alleles are inherited separately from each parent
brown & blue eye colors are separate & do not blend
either have brown or blue eyes, not a blend
Some alleles mask others
brown eye color masked blue

5. Traits are inherited as separate units
For each trait, an organism inherits _________________________________________
a __________________ organism inherits 1 set of chromosomes from each parent
__________________________________
1 from Mom
1 from Dad

6. Remember meiosis! B BB BB = brown eyes bb = blues eyes Bb = brown eyes
Making gametes B BB
BB = brown eyes
bb = blues eyes
Bb = brown eyes b bb B b Bb
Remember meiosis!

7. B BB BB = brown eyes b bb = blues eyes bb B Bb Bb = brown eyes b
How do we say it? BB B
BB = brown eyes
bb = blues eyes bb b Bb B b
Bb = brown eyes

8. B b BB Bb B b Bb bb X male / sperm female / eggs Punnett squares
Bb x Bb
male / sperm B b X BB Bb B b
female / eggs Bb bb

9. Genetics vs. appearance
There can be a difference between how an organism looks & its genetics
appearance or trait = ________________
brown eyes vs. blue eyes
genetic makeup = _________________
BB, Bb, bb
2 people can have the same appearance but have different genetics:

10. Genetics vs. appearance
How were these brown eyes made?
eye color
(brown)
eye color
(brown)
eye color
(brown)
eye color
(blue)
vs. BB B Bb B b

11. Meiosis

12. Homologous Chromosomes
Chromosomes that have a corresponding partner from each parent.

13. homologous chromosomes double stranded homologous chromosomes
Paired chromosomes
Homologous chromosomes
both chromosomes of a pair carry ________________
control same inherited characters
____________________________________
diploid 2n
2n = 4
eye color
(brown?)
eye color
(blue?)
homologous chromosomes
double stranded homologous chromosomes

14. Cell division / Asexual reproduction
Mitosis
produce cells with __________________
identical daughter cells
___________________
clones
____________________________
same genetic information
Aaaargh! I’m seeing double!

15. Single-celled eukaryotes yeast Paramecium Amoeba
Asexual reproduction
Single-celled eukaryotes
yeast
Paramecium
Amoeba
Simple multicellular eukaryotes
Hydra
budding
What are the disadvantages of asexual reproduction?
What are the advantages?

16. Haploid vs. Diploid
A cell that contains only one set of chromosomes is _________________________
A cell that contains both sets of homologous chromosomes is ________________________

17.    + 46 46 92 What if we did, then…. egg sperm zygote
How about the rest of us?
What if a complex multicellular organism (like us) wants to reproduce?
joining of egg + sperm
Do we make egg & sperm by mitosis?
What if we did, then….    46 + 46 92
egg
sperm
zygote

18. Meiosis Goal: Reduce genetic material by half Why? from mom from dad
child
meiosis reduces numbers
of chromosomes by half

19. How do we make sperm & eggs?
Must reduce 46 chromosomes  23
must ______________ the number of chromosomes
______________ 23 46
zygote 23 46
egg 23 46 23
sperm
gametes

20. Meiosis makes sperm & eggs
46 chromosomes to 23 chromosomes
half the number of chromosomes 23 46
egg 46 23
sperm

21. Meiosis = reduction division
special cell division in sexually reproducing organisms
_______________________________
_________________
half
makes _____________
sperm, eggs

22. Meiosis: two cell divisions
homologous
Chromosomes separate
Sister
chromatids
separate
Result: ONLY one copy of each chromosome in a gamete.

23. double stranded gamete
Meiosis 1 overview
double stranded
Divide 1
1st division of meiosis
Line Up 1
prophase 1
metaphase 1
telophase 1
gamete

24. Meiosis I : the reduction division (2n n)
Prophase I
(early)
(diploid)
(late)
Metaphase I
Anaphase I
(haploid)
Telophase I

25. Homologous chromosomes___________ __________________________.

26. Crossing over creates ____________

27. Meiosis II
Gene X
Meiosis II produces gametes with one copy of each chromosome (thus one copy of each gene)

28. 4 Bye Bye 2 Line Up 2 Meiosis 2 overview telophase 2 telophase 1
metaphase 2

29. Meiosis II : the equal division
Prophase II
(haploid x 2)
Metaphase II
Anaphase II
(haploid)
Telophase II

30. Sperm and Egg formation

31. The value of meiosis 1 Consistency over time
meiosis __________________________________________ from generation to generation
Mom
from Mom
Consider the greater variation with 23 pairs of chromosomes = mixing and matching
Dad
offspring
from Dad

32. meiosis _______________________________
The value of meiosis 2
We’re
mixing things
up here!
Change over time
meiosis _______________________________
gametes of offspring do not have same genes as gametes from parents
new combinations of traits
Consider the greater variation with 23 pairs of chromosomes = mixing and matching
from Dad
from Mom
offspring

33. How does this explain: family resemblance & differences!
Why are the kids so similar to the parents but not exact?
Michael & Kirk Douglas
Baldwin brothers
Martin & Charlie Sheen, Emilio Estevez

34. “Putting It All Together” - Fertilization

35. Putting it all together…
gametes 46 23 46 23 46 46 46 46 46 23 46 46
egg 46 46 23
zygote
sperm

36. What Meiosis is About
Meiosis allows the creation of unique individuals
through sexual reproduction.

37. Meiosis & mitosis
Meiosis to make gametes
___________________
Mitosis to make copies of cells
__________

38. MITOSIS MEIOSIS Produces cells for repair,
maintenance, growth, asexual reproduction
Only produces gametes- sex cells (egg/sperm)
Results in
Reduction division results in

40. Mitosis Meiosis # of divisions # of daughter cells
Genetically identical?
Chromosome #
Where
When
Role