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Chapter 9
Meiosis
A. Reproduction
1. ________
Male reaches under his mantle with tentacle,
removes packet of sperm, and insert it into
female’s egg chamber
2. _______
Larva can become adult of either sex
–Depends on conditions
3. __________
• Females in summer (from unfertilized eggs)
• Males in autumn
_______Reproduction
• Single _________ produces offspring
• All offspring are _________________ to
one another and to parent
________ Reproduction
•Two parents contribute to offspring
•All offspring are ________________
Terminology
____________ Chromosomes Carry
Different ___________
• Cell has two of each___________________
• One from mother, other from father
• Paternal and maternal chromosomes carry
different ________
• Offspring inherit new combinations of alleles
•This variation in traits is the basis for
__________________change
Gamete Formation
• Gametes are ___ cells (_______,______)
• Arise from _____cells
ovaries
testes
anther
ovary
Chromosome Number
• Germ cells are ______ (2n)
• Gametes are ________(n)
• Meiosis _________ chromosome number
Meiosis: ____ nuclear divisions, ____
DNA replication
__________
PROPHASE I
DNA replication
METAPHASE I
__________
No DNA
_________
PROPHASE II
METAPHASE II
ANAPHASE I
ANAPHASE II
TELOPHASE I
TELOPHASE II
4 ______
nuclei
Meiosis I and II very similar to mitosis
1. DNA exchange occurs in ________
- Homologues swap _________
Each homologue in the
cell pairs with its partner,
then the partners
separate
PROPHASE I
METAPHASE I
ANAPHASE I TELOPHASE I
2. No ________________ prior to Meiosis II
Crossing Over
These exchange points
are called ___________
•_______________
chromosomes exchange
segments
•Creates new allele
______________ in
offspring
Meiosis II - Stages
Prophase II
Metaphase II Anaphase II Telophase II
Comparison of mitosis and meiosis
Meiosis
End result
Daughter cells
____
__________
Chiasmata?
_____
# of divisions
Purpose
____
________
_______ are
Mitosis
_____
________
_____
___
_______
the physical manifestation of crossing over, a
form of genetic rearrangement.
MITOSIS
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE
MEIOSIS II
PROPHASE II
METAPHASE II
ANAPHASE II
TELOPHASE II
Fig. 9.10a p. 148
Possible
Chromosome
Combinations
•number of possible
combinations of
chromosomes in a
gamete is:
•____ (n is number of
chromosome types)
1
or
or
or
2
3
Factors Contributing to
Variation Among Offspring
1. Crossing over during __________
2. Random _________ of
chromosomes at metaphase I
3. Random combination of ______at
fertilization
Plant Life Cycle
mitosis
multicelled
sporophyte
zygote
fertilization
Diploid
meiosis
Haploid
spores
gametes
multicelled
gametophytes
mitosis
Animal Life Cycle
mitosis
multicelled
body
zygote
fertilization
Diploid
Haploid
gametes
meiosis
Spermatogenesis
secondary
spermatocytes
(haploid)
spermatogonium
(diploid male
reproductive
cell)
primary
spermatocyte
(diploid)
spermatids (haploid)
Growth
Mitosis I,
Cytoplasmic division
Meiosis II,
Cytoplasmic division
Oogenesis
first polar
body
haploid)
oogonium
(diploid
reproductive
cell)
Growth
three polar
bodies
haploid)
primary oocyte
(diploid)
secondary
oocyte
haploid)
Mitosis I,
Cytoplasmic division
ovum
(haploid)
Meiosis II,
Cytoplasmic division
Fertilization
• Male and female ______ unite and
nuclei _____
• Fusion of two haploid nuclei produces
_______ nucleus in the zygote
• Which two gametes unite is _______
– Adds to variation among offspring