#: __ Scientist’s Name: _________
Comp 4d ~ 2
Meiosis
4. Investigate, compare, and contrast cell structures, functions, &
methods of reproduction.
d. Compare and contrast the processes and results of mitosis
and meiosis. (DOK 2)
Comp 4d-2 - Meiosis
DaBook Section 9.2; Textbook Chapter 10-1 (page 270)
Before Meiosis
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Homologous chromosomes are attached to each other
o Homologous chromosomes:
___ copy themselves
Tetrad: __ chromosomes attached to each other
o
__ homologous chromosomes plus __ copies
A copy A
A
A
A
Copies itself
Original homologous
chromosomes
A copy
Tetrad
2 pairs of sister chromatids:
A chromosome and its copy
Meiosis
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Cell division that produces gametes with ___ the number of chromosomes as a body cell
Gametes that are produced are ___ for males and ___ for females
In humans, each sperm and egg cells has ___ chromosomes (which is half of 46, the normal
number of chromosomes)
Sexual reproduction: when haploid egg and sperm cells join together to form a diploid _
Sperm (23) + Egg (23) = __ (46 chromosomes)
Healthy zygotes cannot have more than ___ chromosomes
Once formed, zygotes undergo __ to grow and develop
Mistakes in Meiosis
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_________: when homologous chromosomes don’t separate from each other during meiosis
Result: homologous chromosomes move together into a new gamete giving that gamete ___
chromosomes, while the other new gamete is ___ chromosome
organisms with extra chromosomes _____
organisms with too few chromosomes _____
_______: when organisms have more than the normal number of chromosome sets
o instead of ___ chromosomes, they might have __ that number
o
lethal for __ but not __
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Steps of Meiosis
Meiosis I (__ new cells are formed)
Prophase I:
Metaphase I:
Anaphase I:
Telophase I:
Meiosis II (_ new cells are formed)
Prophase II:
Metaphase II:
Anaphase II:
Telophase II:
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Objectives:
1. Distinguish somatic cells & gametes.
2. Discuss the two types of sex cells.
3. Distinguish haploid & diploid cells.
4. Discuss chromosome numbers.
5. Define homologues, tetrads, chiasmata, synapsis, & nondisjunction.
6. Discuss advantages/disadvantages of meiosis.
7. Discuss the events of meiosis I & meiosis II.
8. Explain how genetic variation occurs.
9. Explain the Law of Independent Assortment.
10. Explain crossing over.
11. Explain trisomy & Down syndrome.
12. Discuss the two types of reproduction.
13. Explaining cloning.
14. Distinguish the types of asexual reproduction.
15. Discuss internal & external reproduction.
16. Explain how you could tell if an organism reproduces sexually or asexually.
17. Explain the process of alternation of generation.
18. How many times do cells divide during meiosis?
19. Explain what happens during Meiosis I to each of these structures:
a. chromosomes?
b. spindle?
c. nucleus?
d. nucleolus?
20. What is synapsis & when does it occur?
21. What is a tetrad?
22. How are genes aligned on homologous chromosomes?
23. Sketch and color a picture of chromosomes during crossing-over. (Figure 10-4, page 272)
24. What type of material is exchanged during crossing-over?
25. Crossing over results in genetic ____.
26. What is independent assortment & what result does it produce?
27. How many cells are formed at the end of Meiosis I & how many copies of chromosomes does
each cell have?
28. Is DNA copied before Meiosis II?
29. How many cells form at the end of Meiosis II and how many chromosomes do they contain?
30. In humans, meiosis occurs in the ____ and in the ____ producing cells called _____.
31. Define spermatogenesis & tell where it occurs.
32. Define oogenesis & tell where it occurs.
33. Mature egg cells are called _____.
34. Explain how only one egg cell is formed instead of four from meiosis.
35. What are the 3 other products of meiosis called?
36. Define asexual reproduction.
37. Name 2 types of asexual reproduction.
38. Name a type of asexual reproduction in unicellular organisms.
39. How do the offspring of asexual reproduction compare to their parents?
40. Define sexual reproduction.
41. How do offspring from sexual reproduction compare to their parents?
42. Is there ever a case in sexual reproduction where offspring can be genetically alike? Explain.
43. What is the evolutionary advantage of sexual reproduction?
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Use the diagram below to answer the following two questions.
44. The diagram shows a pair of chromosomes with different regions on the
labeled. Explain where crossing over could occur on this pair of
chromosomes.
45. When is crossing over most likely to occur?
Matching – Write the letter of the correct meiosis I phase on the line next to its description.
Answers may be used only once or not at all.
___
___
___
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46. crossover can occur frequently
47. homologous pairs are at opposite poles
48. proteins are synthesized
49. spindle fibers guide separated homologous
chromosome pairs toward opposite poles
___ 50. homologous pairs line up at the equator
A. anaphase I
B. interphase
C. metaphase I
D. prophase I
E. telophase
F. anaphase II
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Comparing Mitosis & Meiosis
Mitosis
Meiosis
Number of divisions
Number of Daughter cells
Genetically Identical
Chromosome Number of
Parent Cell
Where Occurs
When DNA replicates
Main Function
Name of Cell Produced
Diploid or Haploid
Daughter Cells
Synapsis of homologous
chromosomes
Involved in growth &
repair
Promotes genetic
variation
Occurs during asexual
reproduction
Also called reduction
division
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