Most important concept:
Without MEIOSIS,
sex and genetics problems would not
exist. |
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Textbook points
Links |
The Textbook
- pp. 176-184. The most important parts of meiosis are on fig
9.2 and CD activity
9.1. The
point of meiosis is that each cell first replicates all of its chromosomes
so that there are for chromatids in each pair of chromosomes (the
paternal and the homologous maternal chromosome). Then it
divides each set of four chromatids (DNA molecules) so that the four daughter cells have
some genetic
differences and only half as many chromosomes.
In Homo sapiens the four daughter
cells are gametes (ova and sperm), which combine to produce a
zygote, the first cell in the unique individual cell line which
clones itself to produce you .
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you do not need to memorize meiotic details.
The most important stages to understand are Prophase I and
Anaphase II.
- comparisons of mitosis and meiosis
as to when & where & why & how many chromosomes &
how much genetic variation? YES! (Table 9.2)
- memorize the details of all the stages of
meiosis? NO.
- memorize the stages of mitosis?
YES. (we hope you already have done this)
- pp. 180-185 emphasize the meiotic contribution to genetic
variation. If you plan to make an A, you should be able to explain
and draw cartoon sequences of crossing-over. Prophase I of
meiosis is the most important thing to understand.
- pp. 186-188 discuss variations in the sex lives of many types of
critters. You don't have to know the details
for this course. And the textbook gets sort of
philosophical about the meaning and purpose of sex. (Some recent
research suggests that sexual reproduction eliminates some undesirable genetic
variations. On the other hand, textbooks nearly always claim
that the purpose of sex is in providing more variation within a species.)
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Meiotic errors (pp. 188-191, karyotypes
used for diagnosis p. 178, and CD Activity 9.2
are interesting to biologists and most
normal people, too, partly because of the medical disorders and also because of their role
in speciation (later in this course) and possibly explaining the purpose of sex.
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Checklist: meiosis, mitosis, daughter cell, gamete,
synapsis (pairing of homologs to form a tetrad of four chromatids),
crossing over, recombination,replication, homologous
chromosomes, homolog, chromatid, centromere, paternal chromosomes,
maternal chromosomes, gene, prophase I, Anaphase II, haploid, diploid,
polyploid, triploid, tetraploid, hexaploid, octoploid,
karyotype, colchicine, chromosome painting, self-fertilization,
outcrossing, life cycle, alternation of generations,
nondisjunction, trisomy, Down syndrome, lethal
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Preview of Test and Quiz questions
> CD Activity 9.2 Prequiz # 1, 2, 3, 4,
5 Postquiz #1, 2, 3
> Content Review (p.
192): #1, 2, 3, 4, 5, 6
> Concept Review
#3, 4, 5
> Figure
Review questions #1,4,5,7, 10, 11
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