Meiosis (Sex Cell Reproduction) PDF

Meiosis (Sex Cell reproduction) Ms. Amilicia Science 7  Human Cells 💧 every cell in your body [EXCEPT SEX CELLS ], has a nucleus with… Joining of...

Meiosis (Sex Cell reproduction) Ms. Amilicia Science 7  Human Cells 💧 every cell in your body [EXCEPT SEX CELLS ], has a nucleus with… Joining of egg and sperm = fertilization * egg formed from fertilization is called the zygote  Diploid Cells 💧 your body forms TWO types of cells * body cells (mitosis cell division) * sex cells (meiosis cell division) * BODY CELLS OUTNUMBER SEX CELLS* --> Body cell has 46 chromosomes --> 23 pairs that are similar **WHEN CELLS HAVE PAIRS OF SIMILAR CHROMOSOMES = DIPLOID (2n) n= chromosome #  HAPLOID CELLS Sex cells DO NOT have pairs of chromosomes = HAPLOID Haploid n= single form (sperm cells & egg cells are haploid) * they only have half the number of chromosomes as body cells  Meiosis {sex cell division} produces 4 haploid (n) sex cells 💧 ensures that offspring will have the same diploid number as parent 💧 After two haploid sex cells combine = a diploid zygote develops Stages of Meiosis (Two part process)  Steps of Meiosis 💧 TWO divisions of the nucleus occur Meiosis I (crossing over occurs) & Meiosis II (similar to mitosis)  Crossing Over= Genetic Variation * Crossing over occurs between two non-sister chromatids. * results in an exchange of genetic material between the maternal and paternal chromosomes. * allows for genetic variation Crossing Over Video  End of Meiosis I * Two New Cells formed * Each new cell has one duplicated chromosome from each similar pair  End of Meiosis II 💧 cytoplasm divides 💧 produces four sex cells each with 23 unpaired chromosomes Somatic cells/ Gametes (Diploid 2n) (Haploid n) > 46 all together > 23 all together > 23 pairs (one set from > Female eggs= 22 + X each parent) * carry traits* > Male sperm = 22 + X or 22 + Y > 44 + XX(female) or 44 + XY(male)  Comparison Mitosis vs. Meiosis  Check for Understanding Human Somatic cells have _____ 46 number of chromosomes Human Sex cells have _____ 23 number of chromosomes Haploid means _______ half the number of chromosomes A fruit fly has 8 chromosomes in its body cell. How many do the 8 daughter cells contain after mitosis? _____ A fruit fly sex cell has ___ 4 chromosomes.  Checking for Understanding Why does crossing over occur during late Prophase 1/ early metaphase 1? Chromosome pairs are close together so genes can exchange ______________________________________________________ Why are there two divisions in meiosis? ____________________ Need to end up with half the number in daughter cells ______________________________________________________ Online Quizzes (Mitosis & Meiosis)