Meiosis Review
Chapter 11
1. The chromosomes in the body cells of most animals and plants occur in
_________.
Pairs
One chromosome in the pair came from the _____ parent and one came from
the _________ parent.
male; female
2. The pairs of chromosomes are called _____________ chromosomes.
Homologous
Each has genes for the ________ __________.
same traits
Is the DNA on these chromosomes identical?
No, the DNA is not identical – their DNA does code for the same
traits
3. Cells with two of each kind of chromosome are called ______________.
The symbol for this is _____.
Diploid; 2n
4. Which type of cells in an organism contain only one of each kind of chromosome?
Cells with one of each kind of chromosome are called ______________.
The symbol for this is _____.
Gametes; haploid; n
5. Two haploid cells unite during __________ resulting in a __________ cell called a
___________.
Fertilization; diploid; zygote
6. Humans have _____ pairs of chromosomes (____ total chromosomes).
23; 46
Humans have 22 pairs of ____________ and 1 pair of ________________.
autosomes; sex chromosomes
7. Mitosis divides a diploid cell into ______ _______ cells. Meiosis divides a
diploid cell into _______ _________ cells.
2 diploid; 4 haploid
8. An organism with 50 chromosomes in a liver cell would have _______
chromosomes in a gamete.
25
9. Meiosis takes place in the _________ of an organism.
Gonads
10. In animals, the process of meiosis produces ________ in males and
________ in females.
Sperm; eggs
11. List the eight phases of Meiosis.
Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II,
Metaphase II, Anaphase II, Telophase II
12. Describe what happens during Interphase. Draw how
a cell may appear during this phase.
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DNA is replicated
Chromosomes are not yet visible
Proteins and RNA are synthesized
Cell is preparing for Meiosis
13. Describe what happens during Prophase I. Draw how
a cell may appear during this phase.
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–
–
–
–
Chromosomes become visible
Nuclear envelope disappears
Spindle forms
Homologous chromosomes pair up to form a tetrad
Crossing over occurs
14. Describe what happens during Metaphase I. Draw how a cell
may appear during this phase.
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–
Spindle fibers attach to centromeres
Homologous chromosome pairs line up
along the equator of the cell
15. Describe what happens during Anaphase I. Draw
how a cell may appear during this phase.
–
Homologous chromosomes separate and
head to opposite ends of the cell
16. Describe what happens during Telophase I. Draw how a cell
may appear during this phase.
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–
Spindle is broken down
Chromosomes uncoil
–
Cytoplasm divides into two cells
17. Describe what happens during Prophase II. Draw how a cell
may appear during this phase.
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–
–
Chromosomes become visible
Spindle forms
If nuclear envelope reformed during
Telophase I, it breaks down now
18. Describe what happens during Metaphase II.
Draw how a cell may appear during this phase.
–
Sister chromatids line up along the equator of
the cell in random order
19. Describe what happens during Anaphase II.
Draw how a cell may appear during this phase.
- The centromeres split and sister chromatids head to opposite
poles of the cell
20. Describe what happens during Telophase II.
Draw how a cell may appear during this phase.
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–
–
–
Nuclei reform
Spindle breaks down
Chromosomes uncoil
Cytoplasm divides into four haploid cells
21. Is there an Interphase between Meiosis I and
Meiosis II?
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No
22. Describe crossing over and when it takes place?
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–
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Homologous chromosomes (one pair of
sister chromatids from the mother and one
from the father) pair up to form a tetrad
The tetrad pairs up so tightly that crossing
over occurs
Nonsister chromatids wind around each
other and genetic material may be
exchanged
23. Explain why genes that are close together would experience
less crossing over than those that are further apart.
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The further the genes are from each other on the
chromosome, the more likely that crossing over would
occur between them
24. The four haploid cells produced by meiosis will become
__________.
–
Gametes
25. What are two ways that meiosis has a role in maintaining the
variability among those in a species?
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Sexual reproduction – different gametes from different
organisms add to the variability in offspring
Crossing over – this allows for genetic recombination so each
gamete is different from the next
26. How does meiosis keep a constant number of chromosomes in
each generation?
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If two diploid gametes fused, each offspring would have double
the chromosome number as the parent. Meiosis reduces the
chromosome number by half in gametes so when they fuse
together the zygote has the same number as the parents
27. List and describe the four types of chromosomal mutations that
can happen when a chromosome breaks and does not repair
itself correctly.
– Deletion – a chromosomal mutation that occurs when part of the
chromosome is left out
– Insertion – a chromosomal mutation that occurs when a part of the
chromosome breaks off and attaches to its sister chromatid
– Inversion – a chromosomal mutation
that occurs when a part of the
chromosome breaks off and is reinserted
backwards
– Translocation – a chromosomal mutation
that occurs when a part of the
chromosome breaks off and is added to
another chromosome
28. _________________ is when homologous chromosomes do
not separate properly during meiosis. This can lead to a gamete
with an _____________________ or ____________________.
Nondisjunction; extra copy of a chromosome; no copy at all
Normal Example
Nondisjunction Examples
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29. What is Monosomy?
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When a zygote gets only one copy of a chromosome (One from
one parent and none from the other)
30. What is the survival rate of most zygotes with monosomy?
What is the exception to this case?
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Most do not survive; The exception is Turner’s Syndrome –
females have only one X chromosome
31. What is Trisomy?
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When a zygote has three copies of a chromosome
(One from one parent and two from the other)
32. Describe two examples of conditions caused by
trisomy.
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Down Syndrome – Three chromosome 21
Klinefelter’s Syndrome – Two X chromosomes and
one Y (XXY)
33. What is a karyotype and how can it help diagnose
chromosomal disorders?
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A picture taken of paired chromosomes
during metaphase – you can see if any
chromosomes are missing or extra
34. By what process do cells become specialized in
structure and function? What happens during this
process?
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Differentiation
Specific parts of the DNA are activated; the parts of
the DNA that are activated determine the function and
specialized structure of a cell.
35. What kind of cells can go through differentiation?
What are the two types?
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–
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Stem cells
Embryonic cells, which have not yet differentiated into
various cell types, are called embryonic stem cells
Stem cells found in adult organisms, for instance in
bone marrow, are called adult stem cells.