Post on 05-Jan-2016
Meiosis Chapter 9
1. ________Male reaches under his mantle with tentacle, removes packet of sperm, and insert it into female’s egg chamber
A. Reproduction
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 ________________
____________ Chromosomes Carry Different ___________
• Cell has two of each___________________
• One from mother, other from father
• Paternal and maternal chromosomes carry
different ________
Terminology
• Offspring inherit new combinations of alleles
•This variation in traits is the basis for __________________change
Gamete Formation• Gametes are ___ cells (_______,______)
• Arise from _____cells
testes
ovaries
anther ovary
Chromosome Number• Germ cells are ______ (2n)
• Gametes are ________(n)
• Meiosis _________ chromosome number
DNA replication
PROPHASE I
METAPHASE I
ANAPHASE I
TELOPHASE I
__________PROPHASE II
METAPHASE II
ANAPHASE II
TELOPHASE II
__________
No DNA _________
4 ______ nuclei
Meiosis: ____ nuclear divisions, ____ DNA replication
Each homologue in the cell pairs with its partner,
then the partners separate
Meiosis I and II very similar to mitosis
1. DNA exchange occurs in ________
- Homologues swap _________
PROPHASE I METAPHASE I ANAPHASE I TELOPHASE I
2. No ________________ prior to Meiosis II
Crossing Over
•_______________ chromosomes exchange segments
•Creates new allele
______________ in
offspring
These exchange points are called ___________
Meiosis II - Stages
Prophase II Metaphase II Anaphase II Telophase II
Comparison of mitosis and meiosis
End result ____ _____
Daughter cells __________________
Chiasmata?
Meiosis Mitosis
__________
_______ are the physical manifestation of crossing over, a form of genetic rearrangement.
# of divisions ____ ___
Purpose _______________
Fig. 9.10a p. 148
PROPHASE METAPHASE ANAPHASE TELOPHASE
MITOSIS
PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II
MEIOSIS II
Possible Chromosome
Combinations or
or
or
1 2 3
•number of possible combinations of chromosomes in a gamete is:
•____ (n is number of chromosome types)
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
multicelled sporophyte
multicelled gametophytes
zygote
gametes spores
meiosisfertilization
mitosis
mitosis
Diploid
Haploid
Animal Life Cycle
multicelled body
gametes
zygote
meiosisfertilization
mitosis
Diploid
Haploid
Spermatogenesis
GrowthMitosis I,
Cytoplasmic divisionMeiosis II,
Cytoplasmic division
spermatids (haploid)
secondary spermatocytes
(haploid)
primary spermatocyte
(diploid)
spermato-gonium
(diploid male reproductive
cell)
Oogenesis
Growth Mitosis I,Cytoplasmic division
Meiosis II,Cytoplasmic division
ovum (haploid)
primary oocyte (diploid)
oogonium (diploid
reproductive cell) secondary
oocyte haploid)
first polar body
haploid)
three polar bodies
haploid)
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