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Announcements
• Test Corrections: 12/6 – 12/16
• Take Biospheres Home
Question of the Day
Question: What is mitosis and what does it
create?
Answer: … … …
Biosphere Report: Part 2
Meiosis Notes &
Vocabulary Sheet
Before Mitosis:
Phases of Mitosis:
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Prophase
Metaphase
Anaphase
Telophase
Unit 5 Vocabulary
19. mitosis- cell division resulting
in 2 identical cells
18. meiosis- cell divisions resulting
in 4 unique cells with half of the
normal number of chromosomes
Introduction
• Meiosis is a type of cell division
that makes cells with half the
number of chromosomes
• How 1N gametes (sex cells) are
created
Unit 5
Vocabulary
16. diploid (2n)- 2 sets
of chromosomes
17. haploid (1n)- 1 set
of chromosomes
Introduction
• Meiosis creates genetic diversity through
the recombination of chromosomes
• DNA is replicated during interphase
beforehand
• In meiosis, the cell will divide twice to
make four 1N cells
Meiosis I
Prophase I
• DNA coils into chromosomes
• Spindle fibers appear
• Homologous chromosomes
pair together, forming a
tetrad
Unit 5 Vocabulary
24. homologs (homologous
chromosomes)- a pair of
corresponding chromosomes, 1 from
each parent
25. tetrad- a pair of duplicated
homologous chromosomes
Meiosis I
Prophase I
• Portions of chromatids may
break off and attach to
adjacent chromosomes; this
is called crossing-over
• Crossing-over exchanges
genetic material between
maternal and paternal
chromosomes
20. crossing over- sections of
chromatids are broken off and
exchanged
Meiosis I
Metaphase I
• Spindle fibers attach
• Tetrads line up in middle of cell
Meiosis I
Anaphase I
• Homologous chromosomes are
pulled apart to opposite ends
of the cell
• Which homologous
chromosome goes to which
end is random
Meiosis I
Telophase I
• Cytokinesis occurs, forming two 1N cells
Meiosis II
Prophase II
• Spindle fibers appear
Meiosis II
Metaphase II
• Chromosomes move toward middle of the cell
Meiosis II
Anaphase II
• Chromatids separate, pulled to opposite ends of each
cell
Meiosis II
Telophase II
• Cytokinesis occurs again
• Four 1N cells are formed
Formation of Gametes
• Sperm and eggs are produced
through meiosis
– makes 4 sperm in testes
– makes 1 ovum (egg) and 3 polar
bodies in ovaries
Unit 5 Vocabulary
9. ovum (ova)- a female sex cell or egg
10. sperm- a male sex cell
8. gamete- sex cells (ex: sperm or ovum)
7. somatic/body cell- a cell in an organism
not used in sexual reproduction
Meiosis vs. Mitosis Lab
Mitosis
•
•
•
•
•
A process of cell division
DNA is replicated in prophase
Produces 2 identical cells
Produces diploid cells (2N)
Produces somatic (body) cells
Meiosis
•
•
•
•
•
A process of cell division
DNA is replicated in prophase
Produces 4 different cells
Produces haploid cells (1N)
Produces gametes (sex cells)