1. Fig. 9-1b, p.138

2. Fig. 9-1c, p.138

3. ovules inside an anther (where ovary (where sexual sexual spores
that give rise to
sperm form)
ovules inside an
ovary (where sexual
spores that give
to eggs form)
Flowering plant
Fig. 9-3a, p.140

4. (where sperm originate) ovary (where eggs develop)
testis
(where sperm originate)
ovary
(where eggs
develop)
Human male
Human female
Fig. 9-3b-c, p.140

5. one chromosome in the duplicated state
centromere
one chromatid
its sister chromatid
one chromosome in the duplicated state
p.141a

6. p.141b

7. cell pairs with its partner,
Each homologue in the
cell pairs with its partner,
then the partners separate.
p.141c

8. two chromosomes (unduplicated) one chromosome (duplicated)
p.141d

9. Fig. 9-5a, p.142

10. Prophase I Metaphase I Anaphase I Telophase I
Meiosis I
newly forming
microtubules of
the spindle
one pair of homologous chromosomes
spindle equator (midway between the two poles)
plasma membrane
breakup
of nuclear
envelope
centrosome with
a pair of centrioles,
moving to opposite
sides of nucleus
Prophase I
Metaphase I
Anaphase I
Telophase I
Chromosomes were duplicated earlier, in
interphase.
Prior to metaphase I, one
set of microtubules had
tethered one chromosome
of each type to one spindle
pole and another set tethered
its homologue to the other spindle pole.
One of each duplicated
chromosome, maternal
or paternal, moves to a
spindle pole; its homologue
moves to the opposite pole.
One of each type
of chromosome has
arrived at a spindle
pole. In most species,
the cytoplasm divides
at this time.
Fig. 9-5a, p.142

11. Fig. 9-5b, p.142

12. Prophase II Metaphase II Anaphase II Telophase II
Meiosis II
there is
no DNA replication
between the two divisions
Prophase II
Metaphase II
Anaphase II
Telophase II
In each cell, one of two centrioles moves to the opposite side of the
cell, and a new bipolar
spindle forms.
By now, microtubules from
both spindle poles have finished a tug-of-war.
The sister chromatids of each chromosome move apart and are now individual, unduplicated
A new nuclear envelope
encloses each parcel of
chromosomes, so there
are now four nuclei.
Fig. 9-5b, p.142

13. a A maternal chromosome (purple) and paternal chromosome (blue) were duplicated earlier, during
interphase. They become visible in microscopes early in prophase I, when hey star to condense to
threadlike form.
b Each chromosome
and its homologous partner zipper
together, so all four chromatids
are tightly aligned.
mom’s
allele A
dad’s
allele a
mom’s
allele A
mom’s
allele A
mom’s
allele B
dad’s
allele b
mom’s
allele B
dad’s
allele b
c Here is a simple way to
think about crossing over. (Chromosomes are still c
ondensed and threadlike,
and each is tightly aligned
with its homologous
partner.)
d Their intimate contact
promotes crossing over
at different places along the length of nonsister chromatids.
e At the crossover site, paternal and maternal chromatids exchange
corresponding segments.
f Crossing over mixes
up maternal and paternal
alleles on homologous
chromosomes.
Fig. 9-6, p.144

14. Fig. 9-6c, p.144

15. Fig. 9-6d, p.144

16. Fig. 9-6e, p.144

17. Fig. 9-6f, p.144

18. Fig. 9-8, p.146

19. secondary spermatocytes (haploid) primary spermatocyte (diploid)
sperm (mature,
haploid male
gametes)
secondary spermatocytes (haploid)
primary spermatocyte (diploid)
diploid male
germ cell
spermatids (haploid)
a Growth
b Meiosis I and
cytoplasmic division
c Meiosis II and cytoplasmic division
Fig. 9-9, p.147

20. three polar bodies (haploid)
first polar body (haploid)
oogonium
(diploid
female
germ cell)
primary oocyte (diploid)
secondary oocyte (haploid)
ovum (haploid)
a Growth
b Meiosis I and cytoplasmic division
c Meiosis II and cytoplasmic division
Fig. 9-10a, p.147

21. Fig. 9-10b, p.147

22. Prophase I Metaphase I Anaphase I Telophase I
In a diploid (2n) germ cell,
duplicated chromosomes
now condense. The bipolar
spindle forms and tethers the
chromosomes. Crossovers
occur between homologues.
Each maternal chromosome
and its paternal homologue
are randomly aligned midway
between the two spindle
poles. Either one may get
attached to either pole.
Homologous
partners
separate
and move
to opposite
poles.
There are two clusters
of chromosomes. New
nuclear envelopes may
form and the cytoplasm
may divide before
meiosis II begins.
Fig. 9-11a, p.148

23. cell, the duplicated chromosomes now condense. Bipolar spindle forms
Mitosis
Prophase
Metaphase
Anaphase
Telophase
In a diploid (2n) body
cell, the duplicated chromosomes now
condense. Bipolar
spindle forms
and tethers the chromosomes.
All chromosomes
aligned at the
spindle equator.
Sister chromatids of each chromosome
moved to opposite
spindle poles.
Two diploid (2n) nuclei form. After cytoplasmic
division, there are two diploid body cells.
Fig. 9-11b, p.149

24. no interphase and no DNA replication between the two nuclear divisions
Prophase II
Metaphase II
Anaphase II
Telophase II
All chromosomes still
duplicated. New spindle
forms in each nucleus,
tethers chromosomes
to spindle poles.
All chromosomes
aligned at the
spindle equator.
Sister chromatids of
each chromosome
moved to opposite
spindle poles.
Four haploid (n) nuclei
form. After cytoplasmic
division, haploid cells
function as gametes
or spores.
Fig. 9-11c, p.149

25. Fig. 9-11d, p.149

26. germ cell germ cell 2n each chromosome duplicated during interphase n
MEIOSIS I
separation of
homologues
MEIOSIS II
separation of
sister chromatids
gametes
gametes 2n
diploid number
restored at
fertilization
zygote
Fig. 9-12, p.150