NAME: ___________________
Meiosis
Mrs. Price----BIOLOGY
Each organism inherits a _______ copy of every gene from each of its “_________” through gametes.
Gametes are formed by a process that ___________ the two sets of genes so that each gamete ends up with just
______ set.
Chromosome Number
-All organisms have _________ numbers of _____________.
A body cell in an adult fruit fly (Drosophila) has __ chromosomes: 4 from the fruit fly's male parent, and 4 from
its ______ parent.
These sets of chromosomes are ___________.
Each of the 4 chromosomes that came from the male parent has a ____________ chromosome from the female
parent.
A cell that contains _______ sets of homologous chromosomes is said to be _________.
The number of chromosomes in a _________ cell is sometimes represented by the symbol ____.
For Drosophila, the diploid number is 8, which can be written as ______
The gametes of __________ reproducing organisms contain only a _________ set of chromosomes, and therefore
only a single set of _______.
These cells are _________. Haploid cells are represented by the symbol ___.
For Drosophila, the haploid number is 4, which can be written as N=4.
Diploid Number (2N) = 46
WHAT WOULD BE THE HAPLOID (N) NUMBER? _____
Phases of Meiosis
Meiosis is a process of __________ division by half by separating __________ chromosomes in a diploid
cell.
Meiosis involves _____ divisions:
• meiosis I
• meiosis II.
By the end of meiosis II, one _________ cell that entered meiosis has become ____ haploid cells.
Meiosis I
__________
__________
__________
___________
_____________ & ____________
Interphase I
• DNA replication forms _________ chromosomes.
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Meiosis I: Prophase I
Each chromosome _______
with its corresponding
homologous
chromosome and forms
a ____________.
-There are ____ chromatids in a
tetrad.
•
When homologous chromosomes form tetrads in meiosis I, they
__________ portions of their ___________ in a process called ____________ over.
Crossing-over produces ____ combinations of alleles.
Meiosis I: ____________ I
• __________ fibers attach to the chromosomes.
Meiosis I: Anaphase I
• The fibers ______ the homologous chromosomes toward __________ ends of the cell.
Meiosis I: Telophase I and ___________
• Nuclear ___________ form.
• The cell separates into _____ cells.
The two cells produced by meiosis I have chromosomes and ________ that are different from each other and
from the _________ cell that entered meiosis I.
Meiosis II
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The ____ cells produced by Meiosis I now enter a second meiotic division.
 Unlike meiosis I, ______ cell goes through chromosome replication.
 Each of the cell’s chromosomes has ___ chromatids.
Meiosis I results in :
 two haploid (N) _________ cells, each with _____ the number of chromosomes as the original cell.
 Prophase II
Meiosis II: Metaphase II
• The chromosomes ____ up in the center of cell.
Meiosis II: Anaphase II
• The sister chromatids ________ and move toward opposite ends of the cell.
Meiosis II: Telophase and Cytokinesis
 Meiosis II results in _____ haploid (N) daughter cells.
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Gamete Formation
In male animals, meiosis results in _____ equal-sized gametes called ______.
In many female animals, only ___ egg results from meiosis. The other three cells, called _____ bodies, are usually
not involved in ____________.
Comparing Mitosis and Meiosis
 Mitosis results in the production of ____ genetically identical _______ cells.
 Meiosis produces _____ genetically different _______ cells.
Mitosis
• Cells produced by mitosis have the ______ number of chromosomes and alleles as the original cell.
• Mitosis allows an organism to _____ and ________ cells.
• Some organisms reproduce _________ by mitosis.
Meiosis
• Cells produced by meiosis have _______ the number of chromosomes as the parent cell.
• These cells are ____________ different from the __________ cell and from each other.
• Meiosis is how __________-reproducing organisms produce gametes.
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