Download BIOL 1406 - Meiosis - Chapter 13

Haploid gametes (n  23)
Egg cell
n
n
Sperm cell
FERTILIZATION
MEIOSIS
Multicellular
diploid adults
(2n  46)
2n
MITOSIS
and development
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Diploid
zygote
(2n  46)
Key
Haploid (n)
Diploid (2n)
Figure 8.12
– Sexual reproduction may convey an
evolutionary advantage by:
• Speeding adaptation to a changing
environment
• Allowing a population to more easily rid
itself of harmful genes
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Meiosis
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter28/animation__how_
meiosis_works.html
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter28/animation__stage
s_of_meiosis.html
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter28/animation__uniqu
e_features_of_meiosis.html
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter28/animation__matur
ation_of_the_follicle_and_oocyte.html
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter28/animation__rando
m_orientation_of_chromosomes_during_meiosis.html
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NONDISJUNCTION IN MEIOSIS II
NONDISJUNCTION IN MEIOSIS I
Meiosis I
Nondisjunction:
Pair of homologous
chromosomes fails
to separate.
Meiosis II
Nondisjunction:
Pair of sister
chromatids
fails to separate.
Gametes
n1
n1
n–1
Abnormal gametes
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Number of
n – 1 chromosomes
n1
n–1
Abnormal gametes
n
n
Normal gametes
Figure 8.20-3
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Table 8.1
Which of the following is an actual
difference between mitosis and meiosis?
1. A single cell is divided into two cells in mitosis and
four cells in meiosis.
2. Mitosis produces haploid cells, and meiosis produces
diploid cells.
3. Mitosis involves two cellular divisions, and meiosis
has only one cellular division.
4. The chromosomes replicate before mitosis and
meiosis, but in meiosis they replicate again between
the first and second divisions.
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The diagram on the right represents the cell cycle through
time of a eukaryotic organism. Which of the four phases of
the cell cycle is the most variable in length of time,
depending on the type of cell?
1. G1 phase
2. S phase
3. G2 phase
4. M phase
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