Science Content Standards Meiosis LN #16 Science Content Standards Genetics 2b. Students know only certain cells in a multicellular organism undergo meiosis. 2e. Students know why approximately half of an individual’s DNA sequence comes from each parent.

Genetics Heredity is passing traits from one generation to another. Genetics is the study of heredity and hereditary variation

What part of the cell carries genetic information? Chromosomes carry genetic information. They are located in the nucleus of cells. Chromosomes contain genes. Genes are a section of DNA that codes for different traits. Genes are passed from one generation to the next.

How many chromosomes are in human cells? Human body cells (somatic cells) have 46 chromosomes. Diploid means to have two of each kind of chromosome. (2n) Chromosomes exist in pairs. One pair coming from mom the other from dad. Homologous chromosomes are paired chromosomes. They contain genes for the same trait. Karyotype = a way to organize chromosomes based on size and type.

Sex cells are not like body cells. Sperm and egg cells are called gametes. Sperm and egg cells have half the number of chromosomes. Haploid mean to have one kind of each chromosome. (n) Gametes (sex cells) are produced by meiosis.

Meiosis Meiosis is a type of cell division where one body cell makes four gametes. Each gamete has half the number of chromosomes as a parent’s body cell. Meiosis only occurs in the reproductive organs (ovaries and testes in animals). Meiosis occurs in two parts, Meiosis I and Meiosis II. Each part contains steps that you might remember from Mitosis. Remember mitosis is the cellular division of body cells, where one cell makes an exact copy of itself.

The Steps of Meiosis I Meiosis I begins with a diploid cell and produces two cells.

The Steps of Meiosis II In meiosis II there are two cells undergoing the same process simultaneously. The end result of meiosis are 4 haploid cells.

Summary What will we be studying in the genetics unit? What are chromosomes and where are they located? How many chromosomes do humans have? Why do chromosomes exist in pairs? What is the difference between diploid and haploid? What is meiosis? What type of cells undergo meiosis?