Leader: Lilli Howard
Course: BIOL/GEN 313
Supplemental Instruction
Instructor: Dr. Rodermel
Iowa State University
Date: 11/18/14
1. List and define the steps of meiosis to the best of your ability.
Meiosis I: 1 2N  2 1N
Prophase I: chromosomes condense and form homologous pairs; crossing over takes place;
nuclear membrane breaks down; spindles begin to form
Metaphase I: Homologous pairs of chromosomes line up along metaphase plate
Anaphase I: homologous chromosomes separate and move toward opposite poles
Telophase I: chromosomes arrive at spindle poles; cytoplasm divides; nuclear membrane forms
Meiosis II: 2 1N  4 1N
Prophase II: chromosomes re-condense
Metaphase II: individual chromosomes line up on equatorial plate
Anaphase II: sister chromatids separate and move toward opposite poles
Telophase II: chromosomes arrive at spindle poles; cytoplasm divides; nuclear membrane
reforms
Meiosis
2. A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA
molecules will be found per cell when this original cell progresses to the following
stages?
a. G2 of interphase 12:24
b. Metaphase I of meiosis 12:24
c. Prophase of mitosis 12:24
d. Anaphase I of meiosis 12:24
e. Anaphase II of meiosis 12:12
f. Prophase II of meiosis 6:12
g. After cytokinesis following mitosis 12:12
h. After cytokinesis following meiosis 6:6
3. List similarities between mitosis and meiosis. Which differences do think are the most
important? Why?
Mitosis:
-single cell division produces 2 genetically identical cells
-chromosome number in progeny cells and the original cell remains the same
-daughter cells and the original cell are genetically identical. No crossing over or separation.
-homologous chromosomes do not synapse
-in metaphase, individual chromosomes line up on metaphase plate
-in anaphase, sister chromatids separate
Meiosis:
1060 Hixson-Lied Student Success Center  515-294-6624  sistaff@iastate.edu  http://www.si.iastate.edu
-2 cell divisions usually result in 4 progeny that are not identical
-daughter cells are haploid and have half the chromosomes as a result of separation of
homologous pairs in a1.
-crossing over in p1 and separation of homologous pairs in a1 produce genetically different
daughters
-homologous chromosomes synapse in p1
-in m1, homologous pairs of chromosomes line up on metaphase plate.
-individual chromosomes line up in m2
-in a1, homologous pairs separate
-in a2, sister chromatids separate
Most importantly, mitosis produces genetically identical cells while meiosis results in a reduction
of chromosome number and allows for genetic variation.
4. A diploid cell (2N) gives rise to two diploid cells (2N) in one step. mitosis
5. A diploid cell (2N) gives rise to four haploid cells (N) in 2 steps. Meiosis
6. The two mechanisms that produce genetic variation in meiosis are crossing over and
random distribution of maternal and paternal chromosomes. (independent assortment)
Event
Mitosis
Meiosis I
Meiosis II
Cell Devision (Y/N)
Yes
Yes
Yes
Chromosomes Reduction
(Y/N)
No
Yes
No
Genetic Variation
Produced (Y/N)
No
Yes
No
Crossing Over (Y/N)
No
Yes
No
Random Distribution of
Maternal and Paternal
Chromosomes (Y/N)
Metaphase
(What lines up on the
metaphase plate?)
Anaphase
(What separates?)
No
Yes
No
Individual
chromosomes
Homologous
pairs
Individual
chromosomes
Chromatids
Homologous
chromosomes
Chromatids
1060 Hixson-Lied Student Success Center  515-294-6624  sistaff@iastate.edu  http://www.si.iastate.edu