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Mysterious Meiosis
Chapter 13 Notes
I. Asexual Reproduction
A.
B. Examples.....
Binary Fision,…. Splitting in two
Budding…”chip off the old block” - hydra
Cloning… genetically indentical individuals
II. Sexual Reproduction
A.
B. Examples...
Most multicellular organisms (including plants)
III. Very Important Vibrant Vocabulary
Heredity: Transmission of ____________ from one generation to the next
Variation: Offspring differ from their _______________ and _______
Genetics: Scientific study of heredity and hereditary variation
Locus: A gene’s specific location along the length of a chromosome
*Genes program cells to make
proteins, proteins produce traits*
Karyotype: Organization of a cell’s
chromosomes by number, size and type
Diploid: A cell with a _________ set of chromosomes (23 pairs = 46
chromosomes)
Homologous Pairs: A pair of chromosomes that have the same
___________, but may have different forms of the genes (1 from _____
and one from __________)
Sex Chromosomes: A special pair of chromosomes that make us girl or boy
XXXYAutosomes: The 22 other pairs of chromosomes
Tetrad: Homologous chromosomes that are copied and stuck at the
centromere
(Four copies of the chromosome, Two from each parent)
Haploid (gametes): Cells with ________ the chromosomes, No homologous
pairs
22 autosomes + 1 sex chromosome = 23 chromosomes
Zygote:
IV. Meiosis...The Details
**Diploid to Haploid **
1. Interphase I
**
2. Prophase I
**
**Synapsis…
**
**Spindle fibers form, nuclear membrane
disappears
3. Metaphase I
**
4. Anaphase I
**
**
5. Telophase I and Cytokinesis
**
6. Prophase II
**
7. Metaphase II
*
8. Anaphase II
*Centromeres break and sister chromatids
(chromosomes) move to the poles
9. Telophase II and Cytokinesis:
*Chromosomes to chromatin
*Four daughter cells are formed
**Ta Da !! Sex cells !!
V. Sources of Variation in Meiosis
A. __________________________________________
When chromosomes line up during Metaphase I, they do so
independently of each other. This results in different combinations
of chromosomes in gametes because every time they line up they do it
differently.
B. __________________________________
During Prophase I, homologous chromosomes pair tightly and pieces of
one chromosome can cross over to the homologous chromosome. This
results in chromosomes that have a combination of maternal and
paternal genes.
C. __________________________________
The egg that is fertilized is one of 8 million chromosome combos. The
sperm that reaches the egg is also one of 8 million combos. This
results in over 64 trillion combos of sperm and egg from one set of
parents (this is without crossovers).
Be sure to look over page 261, Figure 13.10!!! Very possible essay!!!!
VI. Gametogenesis in Humans (pg. 1021)
A. Oogenesis
*Production of ova, mature eggs
*Occurs in the _________________.
*____________________: Stem cells that make eggs
*These stem cells multiply and then begin __________. They stop
meiosis at _________________. The cells at this stage are
called ___________________________. The cells remain
here as follicles until puberty.
*___________________________ stimulates a follicle to grow and
complete ______________ and to start _______________.
*Meiosis II stops....now the cell is called a ____________________.
*Ovulation occurs, the cell then finishes Meiosis II when it is
__________________________________.
B. Spermatogenesis
*Production of mature sperm
*Occurs in the ____________ __________ of the testes.
*____________________: Stem cells that make sperm
*______________ million sperm per ejaculation. Men can ejaculate
daily with no loss of fertility capacity.
C. The difference between Spermatogenesis and Oogenesis
1. In oogenesis meiotic divisions are ______________ (cytokinesis).
*One egg cell is created, three small polar bodies degenerate
In spermatogenesis meiotic divisions are ____________.
*Four sperm are created from each spermatogonia
2. At birth, the ovary contains all of the _____________ it will ever
have. Spermatogonia go through _______________ all
through a man’s life.
3. Oogenesis has long “resting” periods. Spermatogenesis is
uninterrupted.