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Presentation on theme: "MEIOSIS Q2 WK3 D2."— Presentation transcript:


2 One parent cell produces four daughter cells.
Meiosis Meiosis is the type of cell division by which germ cells (eggs and sperm) are produced. One parent cell produces four daughter cells. Daughter cells have half the number of chromosomes found in the parent cell

3 There are 2 parts to Meiosis:
During meiosis, DNA replicates once, but the nucleus divides twice. There are 2 parts to Meiosis: Meiosis 1 Meiosis 2 The 4 new daughter cells have variation of the parent DNA; this is genetic variation

4 Meiosis Terminology Karyotype: Arranging of chromosomes from largest to smallest; pairing up the homologous chromosomes Autosomes: All non-sex chromosomes; (#1-22 for humans) Sex Chromosomes: Chromosomes that determine the sex of an organism (#23 for humans) Set (n): # of different chromosomes. REMEMBER: Haploid = 1set, Diploid= 2 sets

5 Amniocentesis

6 Karyotype of a human Is this person male or female?
How many sex chromosomes are present? How many autosome chromosomes are present? How many homologous pairs of chromosomes are present?

7 Background on Meiosis Meiosis involves 2 divisions of the nucleus
Meiosis STARTS with HOMOLOGOUS CHROMOSOMES Homologous Chromosomes: They are similar in shape, size & genetic content

8 Meiosis 1: 1st Division of Meiosis
Prophase I: Chromosomes condense, nuclear envelope breaks, homologous chromosomes pair at ends. ***Cross-Over: Part of chromatid on 1 homologous chromosome exchanges with the other chromosome*** This is Genetic variation DRAW ME 

9 Meiosis 1: 1st Division of Meiosis
Metaphase I: Homologous chromosomes move to center of the cell by the spindle fibers. Anaphase I: Homologous chromosomes separate and move to opposite poles, BUT sister chromatids stay together. A set of chromosomes moves to each pole Telophase I: The spindle fibers disappear, cells begin to cleave; still, two sets of chromosomes are at opposite poles

10 Meiosis 1

11 End of Meiosis I Once Meiosis I is complete, cytokinesis occurs and the cell splits into 2 haploid cells. These 2 cells enter Meiosis II

12 Meiosis I: STOP & THINK 1. What is the purpose of Meiosis? 2. Describe genetic variation 3. Explain purpose of karyotyping 4. Explain cross-over 5. What major event occurs in Anaphase I ? 6. Are the daughter cells haploid or diploid? Explain

13 Any questions on Meiosis I ?????

14 Meiosis I: Video

15 Meiosis II Prophase II: A new spindle forms around the chromosomes (no longer HOMOLOGOUS CHROMOSOMES) Metaphase II: Chromosomes line up at center & spindle fibers attach to centromere Anaphase II: Centromeres split, chromatids move to opposite poles of cell Telophase II: Nuclear envelope forms around each set of chromosomes & spindles retracts, cell begins cytokinesis

16 Result of Meiosis II 4 HAPLOID cells form as a result of Meiosis II
Haploid = cell containing 1 set of chromosomes

17 Meiosis II: 2nd division of Meiosis

18 Prophase II

19 Metaphase II

20 Telophase II

21 Meiosis I & II Venn Diagram

22 Meiosis Booklet  1. Everyone needs 3 sheets of blank paper 2
Meiosis Booklet  1. Everyone needs 3 sheets of blank paper 2. Fold each one hotdog style 3. Cut straight up the fold (You should have 6 long sheets, only use 5) 4. Label each square with the phases of meiosis the same as the mitosis booklet

23 Meiosis Review Questions 
What type of cells are used in Meiosis? Give examples of these cells. 2. Meiosis is used in sexual reproduction. Explain the process of “cross-over” 3. Draw homologous chromosomes going through cross-over. 4.Meiosis is divided into two parts, why? 5. Define “Haploid” 6. Compare and Contrast Meiosis to Mitosis. In your notebook! 

24 Mitosis & Meiosis Comparison Worksheet 

25 Meiosis & Genetic Variation
Nov. 5th, 2013 Q2 WK4 D2 Meiosis & Genetic Variation

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