HAPPY NEW YEAR!! Please grab the paper from the entry table. You will also need scissors, glue and your journal. PHONES IN THE POCKETS PLEASE
Why do you and your siblings look different?
How did the difference in our DNA occur? If we share the same parents?
Let’s review How do we go from one single cell to an multi-cell organism?
Let’s review: The cell cycle (cell division) Mitosis
Mitosis only creates cells to help our body grow In these cells they have identical DNA
What is Meiosis? Form of cell division in which the number of chromosomes is reduced by half (haploid) to produce sex cells (gametes) used in fertilization. Results in variability of genetic information Eggs or sperm
There are 2 category of cells in our body: somatic and sex cells Somatic Cells(body cells) Any cells that helps in the growth of an organism Is diploid (2n) Example: skin, muscle, blood cells Sex Cells (Gametes) Eggs and Sperm Reproductive cells of an organism Is haploid (n)
Mitosis vs. Meiosis With your partner create a t-chart in your notebook and come up with as many differences between Mitosis and Meiosis (use the diagram to help you)
Mitosis Vs. Meiosis (If you don’t have this information copy it into your notebook) Division of somatic/body cells 1 division = 2 cells Daughter cells identical Diploid cells (2N) =46 Chromosome # identical to parent cell Used for growth and repair Meiosis Division of gametes (sex cells—eggs or sperm) 2 divisions = 4 cells Daughter cells different (crossing over; independent assortment) Haploid cells (N)=23 Chromosome # half of parent cell Used for reproduction
How is Meiosis Different? There are 2 divisions in meiosis Meiosis I and meiosis II The result is 4 daughter cells instead of 2 In meiosis II, the DNA is not replicated again (No interphase) The ending number of chromosomes is 23 in humans (egg has 23 and sperm has 23). This is haploid (n).
How many chromosomes? 38 46 20 200 78
Why do you think sperm and egg are haploid? (have 23 chromosomes)
Meiosis clip https://www. youtube. com/watch Meiosis clip https://www.youtube.com/watch?v=toWK0fIyFlY Stop here Monday.
Tuesday, January 3, 2017 Please grab the papers from the entry table. These are going to be vocabulary flashcards for this unit. Grab some scissors and begin cutting the flashcards. Be ready when the bell rings. PHONES IN THE POCKETS
Use your notes from yesterday to write the definitions of the following words (write the definition on the back of the card). Somatic Cells Sex Cells Gametes Haploid Diploid Daughter Cells
Oogenesis & Spermatogenesis After meiosis the cells have a few more steps before they are eggs & sperm Spermatogenesis: 4 sperms are created after the cell is modified to have flagella Oogenesis: eggs need more cytoplasm and organelles so the cytoplasm of 3 of the cells is absorbed by 1. This results in 1 large egg cell and 3 polar bodies that get reabsorbed by the body.
Spermatogenesis and Oogenesis
Homologous chromosomes Chromosomes that share the same gene location for a particular trait
Tetrad - Structure containing 4 chromatids that form during meiosis.
Crossing over Homologous chromosomes exchange portions of their chromatids. Results in new combinations of genes and different chromatids Happens in PROPHASE
Homologous chromosomes
How does meiosis promote genetic variation? Independent Assortment - Each chromosome is randomly sorted independently of other chromosomes A human who has 46 chromosomes, there are around 8 million possible combinations for a sperm or egg cell.
How does meiosis promote genetic variation? Crossing Over – pairs of homologous chromosomes swap the same segment of genes, forming a chromosome that has some of mom’s and some of dad’s DNA combined.
How does meiosis promote genetic variation? Random Fertilization – the fertilization of an egg and sperm is completely random
Zygote A diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.
Sexual Reproduction Reproduction that involves the exchange of genetic material between two organisms Meiosis
Asexual Reproduction A method of reproduction where a single parent gives rise to two genetically identical offspring, w/o the use of gametes. Mitosis
With your table group, quiz each other using your flashcards With your table group, quiz each other using your flashcards. You will have a quiz on Friday!!! STOP HERE TUESDAY
Wednesday, January 4, 2017 Please grab the papers at the entry table. You will also need scissors, glue, colored pencils and your journal. Please be ready to go when the bell rings. PHONES IN THE POCKETS
Can you determine which children belong to which couple Can you determine which children belong to which couple? Genetic variation is important in creating individuals! From Pearson Education
Answer: The first and last picture belong to couple 1 Answer: The first and last picture belong to couple 1. The middle pictures belong to couple 2.
Steps in Meiosis Meiosis I: Prophase I Metaphase I Anaphase I Telophase I Meiosis II: Prophase II Metaphase II Anaphase II Telophase II
Prophase I DNA condenses and chromosomes become visible. Crossing over occurs Tetrad
Metaphase I Homologous chromosomes line up along the metaphase plate(equator).
Anaphase I Spindle fibers move homologous chromosomes to opposite sides of the cell.
Telophase I & Cytokinesis Nuclear membrane reforms and cytokinesis occurs Result is two diploid daughter cells.
Prophase II Nuclear membrane breaks apart. Spindle fibers form
Metaphase II Chromosomes line up along the equator, not in homologous pairs.
Anaphase II Chromatids separate
Telophase II Nuclear membrane reforms; cytoplasm divides Result is 4 haploid cells.
Practice Questions
Practice Question What inference can be made from the diagram shown? A. The sperm will have double the amount of chromosomes as the parent cell. B. None of the cells made copies of their chromosomes C. The sperm will have half the number of chromosomes as the parent cell.
The diagram above shows the process of meiosis The diagram above shows the process of meiosis. The segregation that occurs during meiosis results in a — A decrease in the total number of cells per organism B reduction in the number of chromosomes per cell C group of genetically identical cells
Compare to mitosis, Meiosis will result in A. 2 Daughter cells B. 4 Daughter Cells C. Less number of daughter cells than mitosis
What is the name of this process? Mitosis DNA replication Crossing over
Which of the following is NOT a result of Crossing over? Both chromosomes with identical genes New combination of genes in each chromosome Genetic variability
Which process of Meiosis is represented by “X”? Mitosis Meiosis I Meiosis II