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Reproduction & Embryology

Reproduction & Embryology. Where do your genes come from?. Diploid and Haploid Cells. How many chromosomes (represented by lines) are found in the human diploid cell? 46 How many chromosomes are found in the human haploid cell? 23

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Reproduction & Embryology

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  1. Reproduction & Embryology Where do your genes come from?

  2. Diploid and Haploid Cells

  3. How many chromosomes (represented by lines) are found in the human diploid cell? 46 How many chromosomes are found in the human haploid cell? 23 Notice that the chromosomes in the diploid cell are in pairs. How many pairs of chromosomes are in the diploid cell? 23 How many pairs of chromosomes are in the haploid cell? 0 What do you think the human body needs haploid cells for? Reproduction Diploid cells, also called somatic cells, are found throughout the body. Haploid cells, also called gametes, are not. Why do you think haploid cells are not found throughout the body? Haploid cells do not have all the DNA and therefore can not function like somatic cells Diploid and Haploid Cells

  4. Diploid and Haploid Cells

  5. Homologous Chromosomes

  6. Homologous Chromosomes

  7. Homologous Chromosomes • Notice how the pairs of chromosomes are arranged in this picture. Briefly describe how they are arranged. Chromosomes are lined up from biggest to smallest (except the last pair). Each pair contains one pick (maternal) and blue (paternal) chromosome. The pairs are homologous. • What is special about the last pair of chromosomes? X and Y are the sex chromosomes – they determine the sex of the individual • What do pairs of chromosomes have in common? Each pair is homologous – meaning it is the same size, shape and carries the same genes.

  8. Homologous Chromosomes • Chromosomes that are the same size, shape and carry the same genes

  9. What are the two types of division shown?   Mitosis and meiosis Which type of division produces Diploid cells? Mitosis Haploid cells? (egg and sperm)  meiosis Which type of cell division, mitosis or meiosis, do you think is normally used to produce new cells for: Growing from a baby to an adult mitosis Healing a wound mitosis Making egg and sperm meiosis

  10. Different Methods of Division

  11. Fertilization

  12. Based on Figure 4, what process creates the egg and sperm? meiosis • Based on Figure 4, what is fertilization? Uniting of the sperm and egg • Fertilization results in a zygote. A zygote is a single cell, yet a baby is millions of cells. What process creates those millions of cells? mitosis • How does meiosis and fertilization creates unique individuals? • Meiosis creates unique sperm and eggs • Fertilization randomly combines them • How does meiosis and fertilization ensure that the amount of genetic information in the zygote is the same as in each body cell of the parents? • Meiosis creates haploid cells • Fertilization combines two haploid cells

  13. Diploid and Haploid Cells

  14. Reproduction & Embryology Where do your genes come from?

  15. The cell cycle remains the same except… G1 Division: meiosis& cytokinesis S G2

  16. Meiosis instead of Mitosis Occurs • Meiosis is a different way to divide the nucleus – it divides it in half literally – creating nuclei with 23 chromosomes instead of 46!

  17. Prophase I • Prophase I is the longest and most complex phase. • All of the events that occurred during prophase of mitosis occur + • Homologous chromosomes come together to form a SYNAPSE (TETRAD). • CROSSING-OVER occurs.

  18. Prophase I Crossing Over Mixed Up DNA!

  19. Metaphase I • Homologous chromosomes line up randomly at the center of the cell. We call this independent assortment.

  20. Metaphase I

  21. Anaphase I • During anaphase the homologous chromosomes in the center of the cell divide.

  22. Telophase I / Cytokinesis • Telophase I two nuclei form and cytokinesis occurs resulting in 2 haploid daughter cells.

  23. Meiosis II • Meiosis II comes directly after cytokinesis. No growth (interphase) takes place. • Meiosis II is broken into 4 events: • prophase II • metaphase II • anaphase II • telophase II. • The steps of Meiosis II are identical to mitosis.

  24. Prophase II • Prophase II is the same as prophase in mitosis.

  25. Metaphase II • Metaphase II is the same as metaphase in mitosis.

  26. Anaphase II • Anaphase II is the same as anaphase in mitosis. Notice that the sister chromatids separate.

  27. Telophase II • Telophase II is the same as telophase in mitosis. • TelophaseII

  28. What is the goal of meiosis? • Meiosis 1 • Goals – reduce the chromosome number & mix up the DNA • Meiosis 2 • Goals – separate sister chromatids and form 4 cells

  29. What 2 important things are accomplished through meiosis 1? • reduce the chromosome number & mix up the DNA

  30. What 2 important processes help mix up the DNA in meiosis 1? • Crossing over (during prophase I) • Independent Assortment (during Metaphase I) 

  31. What is major difference between metaphase 1 and 2? • Metaphase I – homologous pairs line up • Metaphase II – individual chromosomes line up

  32. What is the major difference between anaphase 1 and 2? • Anaphase I – homologous chromosomes separate • Anaphase II – sister chromatids separate

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