Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
MEIOSIS Chapter 11 REVIEW Cell has issues when it grows larger in size Not enough DNA Nutrients and wastes cannot pass the cell membrane Cell solves these problems through the process of cell division Mitosis – the portion of cell division where the nucleus divides MITOSIS Almost every cell of the body uses mitosis to divide the nucleus Somatic cells – cells that are not sex cells/gametes Exs) liver cell, bone cell, brain cell etc. AS LONG AS IT IS NOT SPERM OR EGGS IT USES MITOSIS Cell grows (G1), synthesizes DNA (S), makes molecules and organelles (G2) and then is ready for cell division (mitosis and cytokinesis) STAGES OF MITOSIS 1. Prophase – chromatin condenses into chromosomes and nuclear envelope breaks down, centrioles move and spindle fibers form 2. Metaphase – chromosomes line up in middle of cell and spindle fibers attach to centromere PROPHASE STAGES OF MITOSIS 3. Anaphase – spindle fibers pull at centromere and separate sister chromatids pulling them to opposite ends of the cell 4. Telophase – chromosomes break down into chromatin and nuclear envelope reforms THE END OF MITOSIS After telophase, the cells cytoplasm splits by the process of cytokinesis As a result we are left with… 2 IDENTICAL DAUGHTER CELLS THE NEW STUFF… There are many studies into the process that makes each one of us different Gregor Mendel – a monk born in 1822 who did many studies in the field of genetics Genetics – the study of heredity Why is it that we have traits (eye color, hair color, etc.) similar to our parents, yet we are not all alike? GENETICS Mendel recognized that the offspring of “parents” were similar and began to investigate why this happens He came to the conclusion that the parent organisms must pass on traits in their genetic material These traits are located on their genes (DNA) MENDEL’S PREDICTIONS Mendel was correct about the passing of traits and the idea of genes He wasn’t sure how these events happened but knew 1. 2. An organism must inherit a single copy of every gene from both its “parents” When and organism produces its own cells to pass to offspring, there are 2 sets that must separate from each other so that each cell contains just 1 set of genes STOP! WHAT DOES THIS MEAN?!?! Gametes – the sex cells of an organism Sperm and eggs Mitosis deals with non-gametes (somatic cells) Remember, in mitosis we result in genetically identical cells WE DO NOT WANT GENETICALLY IDENTICAL OFFSPRING!!! TRANSLATION OF MENDEL’S IDEA #2 When and organism produces its own cells to pass to offspring, there are 2 sets that must separate from each other so that each cell contains just 1 set of genes Every cell of the human body contains a specific number of chromosomes (46) In order for offspring to maintain that number of 46 and not end up with duplicate (92), the parent gamete (sex cell) must half their number of chromosomes End result > 23 (mom) + 23 (dad) = 46 offspring chromosomes TRANSLATION OF MENDEL’S IDEA #1 An organism must inherit a single copy of every gene from both its “parents” Remember, each of the 46 chromosomes needs to halved by the parents (to make 23) Parents will only contribute each of those 23 genes one time to their offspring (parents do not want to give multiple copies of the same gene) So, again 23 + 23 = 46 chromosomes total CHROMOSOMES AND GAMETES Remember… Chromosomes – the structures in the cell that carry the genetic material (genes) from the parent cell to the daughter cell Gametes – sex cells or germ cells (sperm and egg) CHROMOSOMES There are many chromosomes in the body that carry information for many different “things” Examples – eye color, hair color, height, 2nd toe length, etc… (everything that makes you, you!) When 2 cells come together from 2 parents, the matching chromosomes must come in contact These matching chromosomes are called homologus Homologous Chromosomes – same chromosome types between mother and father cells CHROMOSOME NUMBERS Haploid – a cell that contains a single set of chromosomes Remember “hap” sounds like half Is usually represented as N Diploid – a cell that contains both sets of homologous chromosomes Remember “di” means 2 (kinda like “bi” – bicycle) Is usually represented as 2N Since the somatic cells of the body are diploid we need the sex cells to be haploid so offspring do not have more chromosomes than necessary WHAT DO DIPLOID/HAPLOID NUMBERS MEAN? Diploid Barbie 2N = 46 chromosomes Diploid Ken 2N = 46 chromosomes Haploid Ken Cell N = 23 chromosomes Haploid Barbie Cell N = 23 + chromosomes Sperm cell Egg cell Equals Diploid Baby 2N = 46 chromosomes HOW ARE HAPLOID GAMETES PRODUCED? Meiosis a process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell Involves 2 distinct divisions 1. 2. Meiosis 1 Meiosis 2 Starts with 1 diploid cell and results in 4 haploid daughter cells that are GENETICALLY DIFFERENT from the parent cell MEIOSIS 1 Prior to meiosis 1, each chromosome is replicated Same as S phase of interphase prior to mitosis Meiosis 1 starts with the cell beginning to divide very similarly to mitosis Unlike mitosis, meiosis 1 has homologous pairing in each step Homologous Pairing – the same chromosome types from mom and dad come together (eye color, hair color, etc.) PROPHASE 1 Homologous chromosomes pair and form a tetrad Since 1 chromosome is made of 2 chromatids, there are 4 chromatids in a tetrad While in their tetrad, homologous chromosomes are able to trade/swap information in a process called crossing over this process results in the exchange of traits (alleles) between the same chromosomes therefore creating new trait combinations One reason why you are different from your parents! REMAINDER OF MEIOSIS 1 Meiosis utilizes the remainder of the cycles as mitosis did separating homologous chromosomes instead of sister chromatids Metaphase 1 – spindle fibers attach to homologous chromosomes Anaphase 1 – spindle fibers separate homologous chromosomes REMAINDER OF MEIOSIS 1 Telophase 1/Cytokinesis – the nuclear envelope reforms around chromosomes and the cytoplasm splits As a result of Meiosis 1, 2 daughter cells are produced that have half the number of genetically different chromosomes MEIOSIS 2 After Meiosis 1, the 2 cells produced proceed to meiosis 2 (there is no chromosome replication) Each of the daughter cells move through Meiosis 2 much in the same way Mitosis occurs Prophase 2 – the centriole move to opposite ends of the cell, the nuclear envelope breaks down Metaphase 2 – chromosomes line up in the middle of the cell and spindle fibers attach to the centromere MEIOSIS 2 Anaphase 2 – the spindle fibers pull on the centromere and split the sister chromatids Telophase 2 & Cytokinesis – the nuclear envelope forms and the cell cytoplasm splits 4 genetically DIFFERENT cells result GAMETE FORMATION The male gamete that is produced is called a sperm (spermatocyte) There are 4 sperm cells that are produced as a result of meiosis The female gamete that is produced is called an egg (oocyte) There is 1 egg cell produced as a result of meiosis The 3 other cells produced are called polar bodies Polar Bodies are not used in reproduction and are considered to be the trash bags of the egg, but can be useful in genetic testing COMPARING MITOSIS AND MEIOSIS Sloppy Copy Mitosis/Meiosis Picture Fold paper down middle Draw Mitosis on left side starting with interphase and ending with cytokinesis beginning with 4 chromosomes (X’s) Draw Meiosis on right side starting with interphase and ending with cytokinesis 2 beginning with 4 chromosomes (X’s) Mitosis/Meiosis Compare/Contrast Graphic Organizer 3 ways they are similar 3 ways they are different