Meiosis Review

Chapter 11

1. The chromosomes in the body cells of most animals and plants occur in _________. PairsOne chromosome in the pair came from the _____ parent and one came from the _________ parent.

male; female2. 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 traits3. Cells with two of each kind of chromosome are called

______________. The symbol for this is _____.

Diploid; 2n4. 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; n5. Two haploid cells unite during __________ resulting in a

__________ cell called a ___________.Fertilization; diploid; zygote

6. Humans have _____ pairs of chromosomes (____ total chromosomes). 23; 46Humans 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.

– 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.

– 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.

– 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.

– 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.

– 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.

– Nuclei reform– Spindle breaks down– Chromosomes uncoil– Cytoplasm divides into four

haploid cells

21. Is there an Interphase between Meiosis I and Meiosis II?

– No

22. Describe crossing over and when it takes place?

– 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.

– 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?

– 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?

– 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

29. What is Monosomy?– 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?

– Most do not survive; The exception is Turner’s Syndrome – females have only one X chromosome

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31. What is Trisomy?– 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.

– 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?

– 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?

– 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?

– 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.