Meiosis Guided Notes
Name: ______________________ Date: ________ ASN:
Goals of Meiosis:
Goal is to produce _____ unique gametes
Occurs in _________ cells in testes and ovaries.
Genetic information is exchanged between maternally and paternally inherited traits.
Contributes to variability or ____________ _______________.
Homologous Chromosomes
Three characteristics that homologous chromosomes have
1.
2.
3.
Meiosis or “_________________________________________________”
Results in _________________ of chromosome number from __________ (cell has _______ copies of
each chromosome, one maternal and one paternal chromosome)
…to ________ (cell has only ________ copy of each chromosome, either maternally-derived or
paternally-derived chromosome)
Chromosomes are _______ sister chromatids at this point
Haploid and Diploid
Cells having ______ sets of chromosomes are diploid (____n). Ex. All body cells (Somatic) such as blood
cells, skin cells, muscle cells, zygote
________ cells (____n) have only one set of chromosomes. Ex. Sperm and egg (AKA- gametes).
Sex Chromosomes and Autosomes
Sex chromosomes are chromosomes that determine the _________ of an organism.
All of the other chromosomes in an organism are _____________. All autosomes come in
_____________ pairs. One chromosome comes from mom the other from dad. They are homologous
because they have the same type of genes on them. (_________=same)
Development of the Gametes
__________________________ is the process by which sperm cells are produced.
__________________________is the process that produces mature egg cells.
Interphase
Cell is growing
________ is replicated (each chromosome is copied)
*There is now the equivalent of four copies of each chromosome in the cell (___ n)
Prophase 1
__________ condenses into _____________________
Homologous chromosomes pair up = TETRADS
CROSSING OVER:
*Occurs in Prophase I
*Paternal and Maternal homologous chromosomes are paired up and intertwine,
exchanging information to create new and unique chromosomes.
Metaphase 1
_____________________ attach to spindle fibers at the ____________________.
__________________chromosomes line up at the equator.
Anaphase 1
Homologous chromosomes move to opposite poles of the cell.
Telophase 1
___________________ ______________ break down.
Chromosomes uncoil into nuclei.
Cell divides into _________ intermediate cells each with _______ chromosomes.
Prophase 2
Spindle fibers form.
___________________ condenses into ________________
Metaphase 2
Chromosomes line up on the _________.
Anaphase 2
Sister _______________are pulled apart at the _____________and moved to opposite poles of the cell.
Telophase 2
___________________ reach the poles.
Spindle fibers disappear and nuclear membranes reform.
AND FINALLY… Cytokinesis
Meiosis results in _____________ genetically unique haploid cells, each with _______ chromosomes.
Why is Meiosis important?
Genetic diversity.
*Genetic issues possessed by one parent may not be passed on to offspring.
*Depending on how the chromosomes line up at the equator, four gametes with four different
combinations of chromosomes can result.
*Genetic variation also is produced during crossing over and during fertilization, when gametes
randomly combine.