Warm-Up Questions 1. What are the stages of mitosis in order? 2. The diagram represents a cell process. Which statement regarding this process is true? A. Cell B contains the same genetic information that cells A and C contain B. Cell C has DNA that is only 50% identical to cell B C. Cell A has DNA that is only 75% identical to cell C D. Cells A, B, and C contain completely different genetic information 3. How many chromosomes do most human cells have?
Warm-Up Questions: Check your answers 1. What are the stages of mitosis in order? Prophase, Metaphase, Anaphase, and Telophase 2. The diagram represents a cell process. Which statement regarding this process is true? A. Cell B contains the same genetic information that cells A and C contain B. Cell C has DNA that is only 50% identical to cell B A C. Cell A has DNA that is only 75% identical to cell C D. Cells A, B, and C contain completely different genetic information 3. How many chromosomes do most human cells have? 46 total chromosomes
FYI: 1. The Cell Division test is on Friday! 2. The midterm is next Tuesday!
Meiosis & Sexual Reproduction 2006-2007
Cell division / Asexual reproduction Mitosis (asexual reproduction) produces cells with same information identical daughter cells exact copies clones same number of chromosomes same genetic information -used by single cell organisms and somatic (body) cells like bacteria or skin cells Aaaargh! I m seeing double!
How about more complex organisms? 1. Mitosis is good for simple organisms, but what if a complex multicellular organism (like us) wants to reproduce? joining of egg + sperm (fertilization) 2. Do we make egg & sperm by mitosis? No! What if we did, then. 46 + 46 92 egg sperm zygote Doesn t work!
3. Meiosis makes sperm & eggs 4. In humans: 46 homologous chromosomes to 23 single chromosomes (half the number of chromosomes) 46 23 meiosis egg 46 23 diploid sperm haploid
5. What are Paired/ Homologous chromosomes? Homologous chromosomes both chromosomes of a pair carry matching genes control same inherited characters 6. homologous = same information diploid 2n 2n = 4 eye color (brown?) eye color (blue?) homologous chromosomes double stranded homologous chromosomes
7. Egg cells and sperm cells are called haploid because they only have a single set of chromosomes.
8. Diploid vs. Haploid Cell Diploid full set of chromosomes (2n) mitosis all cells but gametes (sex cells) Haploid half set of chromosomes (n) meiosis gametes only
9. How do we create haploid cells? Meiosis = reduction division 10. Meiosis A. special cell division in sexually reproducing organisms B. reduce number of chromosomes 2n 1n diploid haploid half C. makes gametes sperm, eggs
What actually happens during meiosis?
11. How do we make sperm & eggs? Must reduce 46 chromosomes 23 must half the number of chromosomes haploid 46 46 23 egg meiosis 46 23 23 23 zygote fertilization sperm gametes
12. Meiosis I (very similar to mitosis) Copy DNA and crossing over occurs Chromosomes Line Up Cell Divides
12. Meiosis II (2): Kind of like meiosis I, except the DNA doesn t replicate before Chromosomes Line Up Cell Divides
12. It looks like this when it s combined
13. Meiosis Summary: Interphase: Before meiosis begins, genetic material is duplicated. First division of meiosis (Meiosis I) Prophase 1: DNA condenses into chromosomes. Crossing-over can occur during the latter part of this stage. Metaphase 1: Homologous chromosomes align in the middle (Meta=middle) Anaphase 1: Homologous pairs separate and move towards the poles. Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the homologous pair. Second division of meiosis: Gamete formation (Meiosis II) Prophase 2: DNA does not replicate. Metaphase 2: Chromosomes align at the equatorial plate (in the middle). Anaphase 2: Sister chromatids migrate separately to each pole. Telophase 2: Cell division is complete. Four haploid daughter cells are obtained.
How does meiosis lead to a new organism?
14. How does meiosis lead to a new organism? meiosis fertilization mitosis + development gametes 46 23 meiosis 46 egg 46 23 sperm 23 23 fertilization 46 46 46 46 46 46 46 46 zygote mitosis mitosis & development
15. Cycle of Life: (when do the different types of cell division happen during our lives?)
Fertilization
What do these 46 human chromosomes look like in real life? 16. Karyotypes are used to see the number and appearance of the chromosomes an organism has
Random Fact: The sperm cell (male sex cell) determines the sex of the offspring. The 23 rd chromosomes (X or Y) is the genetic difference between men and women.
Karyotype: Human Female (Female because it Notice: There are 23 pairs of chromosomes 23x2=46 total has two X chromosomes, no Y)
Karyotype: Human Male (Male because it has X and Y chromosomes) Notice: There are 23 pairs of chromosomes 23x2=46 total
17. How does meiosis increase genetic 1. 2. variation? 3.
How does meiosis create genetic variation?
18. Advantages of Meiosis- it increases genetic variation No two offspring (except identical twins) are the same, giving the species a better chance of surviving.
19. Disadvantage of Meiosisorganisms cannot reproduce by themselves, and it takes more time and energy to reproduce/ find a partner to reproduce with.
Congrats! You finished the notes! Now, please flip your note paper to the back: 1) get a textbook and answer the guided reading questions. 2) Use the last two slides (scroll down) to help you answer the other review questions on the paper.
Meiosis & mitosis Meiosis to make gametes sperm & egg Mitosis to make copies of cells growth repair development
Reproduction Review: Sexual Reproduction 2 parents - male and female involves gametes - sperm and egg offspring genetically different can be internal or external fertilization MEIOSIS Asexual Reproduction 1 parent offspring produced by a part or division of the parent CLONES - offspring genetically identical MITOSIS