Bellringer What is happening in metaphase? What is happening in anaphase? How many cells are created in mitosis? What about meiosis? Where in the human body does meiosis occur?
Test on the 16th (B) and 13th (A) Meiosis Test on the 16th (B) and 13th (A)
Stages 2 divisions to make 4 genetically different cells from one cell First Divisionmeiosis I Prophase I Metaphase I Anaphase I Telophase I Cytokinesis I
Prophase II Metaphase II Anaphase II Telophase II Cytokenesis II Second Division Prophase II Metaphase II Anaphase II Telophase II Cytokenesis II
Meiosis I The homologous chromosomes begin to pair up-called synapsis The pairs in meiosis I are called tetrads The goal of meiosis I is to break apart tetrads Meiosis II Chromatids separate and migrate to polls Chromatids arrive at polls, and cell divides The result is four cells with half the number of chromosomes as the starting cell
Animations Mitosis animation mitosis.htm Meiosis animation meiosis.htm
Make a Venn Diagram Mitosis Meiosis Both
Characteristics of Meiosis
Vocabulary Somatic Cells “body cells” non-sex cells Germ cells Cells in reproductive organs cells Gamete sex cells (sperm and egg) Autosomes non sex chromosomes (the other 22 pairs) Sex chromosomes- chromosomes which determine male and female X and Y (one pair)
Genetic Recombination Mixing of genetic information between chromosomes of the same organism or between two different organisms Causes diversity in offspring Can be done by man or natural When done by man, called genetic engineering when scientists transplant genetic material from one organism to another. When natural crossing over
Crossing Over When a gene or piece of DNA switches places with a gene or piece of DNA from a homologous chromosome In other words, material from each parent can be switched between homologous chromosomes If this occurs, genetic information can be exchanged Prophase I of Meiosis I Increases genetic diversity
Crossing over
Independent Assortment Alleles of different genes assort independently of one another during gamete formation metaphase of meiosis I the gamete can end up with any combination of paternal or maternal chromosomes Increases genetic diversity In humans there are 223 different combinations
Independent Assortment
Law of Segregation when any individual produces gametes, the alleles separate so that each gamete receives only one copy. A gamete will receive one allele or the other. In meiosis the moms and dads chromosomes get separated and the alleles with the traits of a character are segregated into two different gametes.
Random Fertilization Men produce millions of sperm, and each sperm has an equal chance of fertilizing the egg Women produce multiple eggs per month, but only one is used for fertilization. The rest are used as polar bodies Resulting is a randomly produced zygote with random alleles from each parent.
Haploid (n) Haploid a cell that has only one set of chromosomes This means that the cell will have 23 chromosomes Sex cells are haploid cells A male haploid sperm cell and a female haploid egg cell will come together to make a diploid zygote (one celled embryo)
Diploid (2n) Diploid a cell or organism that has two sets of chromosomes Diploid cells have 46 chromosomes One from mom and one from dad Two haploid cells come together and make a diploid organism A diploid cell would be your somatic cells. Which are…?
Spermatogenesis The process of creating sperm Male meiosis Every one meiosis cycle produces 4 sperm Males do this constantly with little regulation
Oogenesis Female meiosis Process of making egg cells Only one egg cell per meiosis cycle Only one meiosis cycle per month The other four cells, called polar bodies, are going to become food for the potential fertilized egg In other words, three out of the four cells do not become eggs, they become polar bodies Ovum the mature egg once it has grown. It is ready to be fertilized by a sperm
Concept Four Square Draw a picture to represent the concept Describe in your own words the major concept of choice Draw a picture to represent the concept Tell me how it is different than another concept we covered today Why did we learn about the concept? (your answer can’t be because its on the test) Concept