1. Students….
Test corrections due Monday
GREEN sheets stay in my classroom…please & thank you
Learning Log is posted
Cell phones in bin….off or muted…please & thank you

2. Educational Service Trip to the Dominican Republic – July 2017
Information Meeting – Thursday, October 6:30PM
Career Center Media Center
Only 25 students can participate – all students eligible.
Contact Mr. Sean Bennett (Career Center) for more details.

3. Students….
Misconceptions….write these down please
Reproductive isolation = species definition
Horse & donkey are EACH reproductively isolated…
NOT the mule
- Populations adapt…NOT species
What do you know about meiosis?

4. Chapter 13 Meiosis Essential Questions
LO 3.10 The student is able to represent the connection between
meiosis and increased genetic diversity necessary for
evolution.
LO 3.28 The student is able to construct an explanation of the
multiple processes that increase variation within a
population.

5. Ch 13 Meiosis and Sexual Life Cycles
1. What do you know about chromosomes?
Made of chromatin – DNA + protein
23 pairs (46 total)
22 autosomes + 1 sex chromosome
XX - ♀ - female
XY - ♂ - male
What is the difference between haploid & diploid?
- haploid (n )
- cells with 1 set of chromosomes
- gametes - sperm & egg
- diploid (2n)
- somatic cells
- 2 sets of chromosomes (1 set – mom & 1 set dad)
Meiosis creates haploid gametes that unite to produce a diploid zygote.

6. Figure 13.4 Describing chromosomes
Key
Maternal set of
chromosomes (n = 3)
Paternal set of
2n = 6
Two sister chromatids
of one replicated
chromosome
Two nonsister
chromatids in
a homologous pair
Pair of homologous
chromosomes
(one from each set)
Centromere

7. Ch 13 Meiosis and Sexual Life Cycles
What do you know about chromosomes?
What is the difference between haploid & diploid?
Where does meiosis occur in us?
- testes
- ovaries
Key
Haploid (n)
Diploid (2n)
Haploid gametes (n = 23)
Ovum (n)
Sperm
Cell (n)
MEIOSIS
FERTILIZATION
Ovary
Testis
Diploid
zygote
(2n = 46)
Mitosis and
development
Multicellular diploid
adults (2n = 46)

8. (b) Plants and some algae (c) Most fungi and some protists
Ch 13 Meiosis and Sexual Life Cycles
What do you know about chromosomes?
What is the difference between haploid & diploid?
Where does meiosis occur in us?
Let’s check out meiosis in other organisms…plants & fungi
Diploid
multicellular
organism
Key
MEIOSIS
FERTILIZATION n 2n
Zygote
Gametes
Haploid multicellular
organism (gametophyte)
Haploid
Mitosis
Spores
(a) Animals
(sporophyte)
(b) Plants and some algae
(c) Most fungi and some protists

9. Ch 13 Meiosis and Sexual Life Cycles
What do you know about chromosomes?
What is the difference between haploid & diploid?
Where does meiosis occur in us?
Let’s check out meiosis in other organisms…plants & fungi.
What happens in meiosis? An overview.
Preceded by DNA replication
2 consecutive cell divisions
meiosis I – separation of homologous chromosomes
meiosis II – separation of sister chromatids
Makes 4 unique daughter cells. Genetically different from
- each other
the parent cell

10. Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number
Interphase
Homologous pair
of chromosomes
in diploid parent cell
Chromosomes
replicate
Homologous pair of replicated chromosomes
Sister
chromatids
Diploid cell with
replicated
chromosomes 1 2
Homologous
separate
Haploid cells with
replicated chromosomes
Sister chromatids
Haploid cells with unreplicated chromosomes
Meiosis I
Meiosis II
Meiosis I creates haploid cells
with replicated chromosomes.

11. Ch 13 Meiosis and Sexual Life Cycles
What do you know about chromosomes?
What is the difference between haploid & diploid?
Where does meiosis occur in us?
Let’s check out meiosis in other organisms…plants & fungi.
What happens in meiosis? An overview.
What happens during meiosis? The specifics.

12. Students
Staple test corrections in this order...please...& then place in box
Top – Results sheet
Written corrections
Scantron
Bottom – Test copy
Transport – Wednesday
Phones in bin…off or muted…please & thank you

13. Figure 13.8 The Meiotic Division of an Animal Cell
Centrosomes
(with centriole pairs)
Sister
chromatids
Chiasmata
Spindle
Tetrad
Nuclear
envelope
Chromatin
Centromere
(with kinetochore)
Microtubule
attached to
kinetochore
Tetrads line up
Metaphase
plate
Homologous
chromosomes
separate
Sister chromatids
remain attached
Pairs of homologous
chromosomes split up
Chromosomes duplicate
Homologous chromosomes
(red and blue) pair and exchange
segments; 2n = 6 in this example
INTERPHASE
MEIOSIS I: Separates homologous chromosomes
PROPHASE I
METAPHASE I
ANAPHASE I
Prophase I (90% of meiosis)
Chromosomes condense
Centrosomes move apart
Nuclear envelope disappears
Synapsis occurs forming tetrads
Chromsomes line-up gene-by-gene
Crossing over takes place at chiasmata

14. MEIOSIS II: Separates sister chromatids
TELOPHASE I AND
CYTOKINESIS
PROPHASE II
METAPHASE II
ANAPHASE II
TELOPHASE II AND
MEIOSIS II: Separates sister chromatids
Cleavage
furrow
Sister chromatids
separate
Haploid daughter cells
forming
During another round of cell division, the sister chromatids finally separate;
four haploid daughter cells result, containing single chromosomes
Two haploid cells
form; chromosomes
are still double
Meiosis II – same as mitosis (separation of sister chromatids)

15. Ch 13 Meiosis and Sexual Life Cycles
What do you know about chromosomes?
What is the difference between haploid & diploid?
Where does meiosis occur in us?
Let’s check out meiosis in other organisms…plants & fungi.
What happens in meiosis? An overview.
What happens during meiosis? The specifics.
What are the differences between mitosis & meiosis?
What are the 3 ways meiosis creates genetic variation?
Crossing over (prophase I)
Independent assortment of tetrads (metaphase I)
Random fertilization

16. Figure 13.11 The results of crossing over during meiosis
Prophase I
of meiosis
Nonsister
chromatids
Tetrad
Chiasma,
site of
crossing
over
Metaphase I
Metaphase II
Daughter
cells
Recombinant
chromosomes
Prophase I – crossing over occurs
New chromosome combinations
non-sister chromatids are exchanged
2 – 3 times per chromosome in us

17. Figure 13.10 The independent assortment of homologous chromosomes in meiosis
Key
Maternal set of
chromosomes
Paternal set of
Possibility 1
Two equally probable
arrangements of
chromosomes at
metaphase I
Possibility 2
Metaphase II
Daughter
cells
Combination 1
Combination 2
Combination 3
Combination 4
223 possible combinations in humans

18. Ch 13 Meiosis and Sexual Life Cycles
What do you know about chromosomes?
What is the difference between haploid & diploid?
Where does meiosis occur in us?
Let’s check out meiosis in other organisms…plants & fungi.
What happens in meiosis? An overview.
What happens during meiosis? The specifics.
What are the differences between mitosis & meiosis?
What are the 3 ways meiosis creates genetic variation?
Independent assortment of chromosomes (metaphase I)
Crossing over (prophase I)
Random fertilization
223 = 8 million sperm x
223 = 8 million egg
64 trillion unique combinations
Genetic variation contributes to evolution via natural selection

20. Ch 13 Meiosis and Sexual Life Cycles
What do you know about chromosomes?
What is the difference between haploid & diploid?
Where does meiosis occur in us?
Let’s check out meiosis in other organisms…plants & fungi.
What happens in meiosis? An overview.
What happens during meiosis? The specifics.
What are the differences between mitosis & meiosis?
Meiosis is a reduction division…mitosis cells have the same number of chromosomes.
Meiosis creates genetic variation…mitosis produces a clone.
Meiosis is 2 consecutive nuclear divisions….mitosis just 1.

21. Figure 13.9 A comparison of mitosis and meiosis
Prophase
Duplicated chromosome
(two sister chromatids)
Chromosome
replication
Parent cell
(before chromosome replication)
Chiasma (site of
crossing over)
MEIOSIS I
Prophase I
Tetrad formed by
synapsis of homologous
chromosomes
Metaphase
Chromosomes
positioned at the
metaphase plate
Tetrads
Metaphase I
Anaphase I
Telophase I
Haploid
n = 3
MEIOSIS II
Daughter
cells of
meiosis I
Homologues
separate
during
anaphase I;
sister
chromatids
remain together
Daughter cells of meiosis II n
Sister chromatids separate during anaphase II
Anaphase
Telophase
Sister chromatids
separate during
anaphase 2n
Daughter cells
of mitosis
2n = 6