1. Chapter 7 Meiosis Review

2. The Basics of Meiosis Animals and plants practice _______ reproduction, with parents passing chromosomes to their offspring. Because each child receives unique combinations of chromosomes from the _______, each child differs from the parents. sexual parents

3. The Basics of Meiosis (cont.) The chromosomes of each parent exist in pairs called homologues, or __________ chromosomes. The pairs are identical in size, shape, construction, and the ______ they contain. However the homologues within an organism may contain different versions, or _____, of those genes. homologous genes alleles

4. The Basics of Meiosis (cont.)

5. With 23 pairs of chromosomes, humans have a total of __ chromosomes. This total number of chromosomes is called the _______ number. 46 diploid

6. The Human Life Cycle The human life cycle involves two types of cell division. – ___________ Mitosis Meiosis

7. The Human Life Cycle (cont.) Mitosis is involved in the ________ of a child and repair of tissues. Meiosis is a special form of cell division associated with _______ reproduction. –Meiosis produces special reproductive cells called __________ (eggs and sperm in humans). –Gametes have only _____ set of chromosomes. growth sexual gametes 1

8. The Human Life Cycle (cont.) In males, meiosis is part of _______ production (spermatogenesis). In females, meiosis is part of ______ production (oogenesis). During fertilization, an egg and sperm unite to form a ________, restoring the chromosomes to 46 total. sperm egg zygote

9. Overview of Meiosis (cont.) During meiosis I, the _______________ chromosomes pair up to form sister chromatids of two homologous chromosomes. Later in meiosis I, the homologous pairs _________ to provide one member of each homologous pair to each daughter cell. After meiosis I, the daughter cells have half the number of ______________, but each chromosome consists of two sister chromatids. homologous separate chromosomes

10. Overview of Meiosis (cont.) During meiosis II, the sister chromatids are ____________. The two divisions of meiosis insure that the _________ produced by an individual have unique combinations of homologous chromosomes. separated gametes

11. Overview of Meiosis (cont.) A dyad is a chromosomes composed of two sister chromatids A tetrad is the pairing of homologous chromosomes

12. Crossing-Over While a homologous chromosomes pair up during meiosis I, the homologues may exchange genetic material by crossing- over during __________. Crossing-over recombines the alleles of the _____________ chromosomes, creating new combinations and increasing the genetic variability of the gametes. Prophase I homologous

13. Crossing-Over (cont.)

14. The Importance of Meiosis One reason meiosis is important is that it maintains the same number of ___________ in each new generation. Another reason meiosis is important is that it contributes new ___________ of alleles to each new generation. chromosomes combinations

15. The Phases of Meiosis The same four stages of mitosis occur during meiosis. The four stages occur _____, once during meiosis I and again during meiosis II. prophase metaphase anaphase telophase twice

16. The First Division – Meiosis I Significant events occur during prophase I of meiosis. –The spindle appears between the separating centromeres. –The h_________ chromosomes pair up as they condense. –C______-over between homologous chromosomes may occur. At metaphase I, the pairs of homologous chromosomes are attached to the spindle and are aligned at the spindle e________.

17. The First Division – Meiosis I (cont.) The homologous chromosomes are separated during a________ I. Anaphase I is the point at which the diploid cell becomes h_______. During telophase I, the nuclear m________ reforms around the now haploid nuclei.

18. The First Division – Meiosis I (cont.) Tetrad is the pairing of homologous chromosomes A dyad is a chromosomes composed of two chromatids

19. The Second Division – Meiosis II The events that occur during m______ II are essentially the same as those that occur during mitosis. As prophase II begins, a s_______ appears and the nuclear membrane and nucleolus disappear. During metaphase II the chromosomes made up of two chromatids line up at the spindle e_____.

20. The Second Division – Meiosis II (cont.) The sister chromatids of the chromosomes s_______ during anaphase II and begin migrating towards the poles. The spindle d_________ and the nuclear envelope reforms in telophase II. Cytokinesis occurs to complete the meiosis. In summary, a single diploid cell undergoes meiosis to produce ____ haploid gametes.

21. The Second Division – Meiosis II (cont.) A dyad is a chromosomes composed of two chromatids

22. Meiosis Compared to Mitosis Meiosis requires ___ nuclear divisions while mitosis requires only one. Meiosis produces ____ daughter nuclei while mitosis produces only two. Both meiosis and mitosis are typically followed by c_________.

23. Meiosis Compared to Mitosis (cont.) After meiosis, the daughter nuclei are haploid and contain h___ the chromosome number of the parent cell. Following mitosis, the daughter cells have the s____ chromosome number as the parent cell.

24. Meiosis Compared to Mitosis (cont.) The daughter cells of meiosis are g_________ dissimilar from the parent cell. The daughter cells of mitosis are genetically i_______ to the parent cell.

25. Meiosis Compared to Mitosis (cont.) A dyad is a chromosomes composed of two chromatids Tetrad is the pairing of homologous chromosomes

26. Occurrence Meiosis occurs only at specific times during the life cycle of sexually reproducing organisms. Meiosis in humans occurs only in the t_____ and o______. Mitosis is common and occurs throughout the b____.

27. Process There are several events that distinguish meiosis I from mitosis. Homologous chromosomes pair up during m_______ and crossing-over can occur during prophase I. This does not occur during mitosis.

28. Process The homologous p____ of chromosomes align at the spindle equator during metaphase I of meiosis. In mitosis, the chromosomes align during metaphase. During anaphase I, the homologous chromosomes s________ while in anaphase of mitosis, the sister chromatids separate.

29. Process (cont.) A dyad is a chromosomes composed of two chromatids Tetrad is the pairing of homologous chromosomes

30. Process (cont.) The events of meiosis II are the same as mitosis.

31. Process (cont.) A dyad is a chromosomes composed of two chromatids Tetrad is the pairing of homologous chromosomes