Bellwork: Identify which “PHASE” the cells are going through and DRAW that cell.

Standard: (B.6G) recognize the significance of meiosis in sexual reproduction Essential Question: What is meiosis and how is it different than mitosis?

Chromosomes

Chromosomes are coiled DNA located in the cell nucleus. An organism inherits one chromosome from each parent. How many parents do you have? So you have ____ sets of each chromosome. 2 copies of each chromosome = homologous chromosomes

A cell that contains 2 sets of homologous chromosomes is said to be diploid. 2N = diploid cell. Because N = number of chromosomes

Sexual Reproduction & Our Cells

On a cellular level, what happens during sex? Biologically speaking, what’s the point of sex?

Sexual reproduction combines DNA from 2 parents. Gametes are sex cells, also known as the sperm and the egg. When each parent forms gametes (egg, sperm) in their body, they can only have 1 set of chromosomes instead of 2. During fertilization, = 2 sets of chromosomes.

When gametes (sex cells) are formed, there must be a process that separates the two sets of genes so that each gamete ends up with just one set.

Because gametes contain only 1 set of chromosomes they are said to be haploid. N = haploid N= number of sets of chromosomes in the cell

Meiosis

Meiosis is a process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell. ** Meiosis is how gametes are produced**

Meiosis usually involves two divisions. By the end of meiosis, the 1 diploid cell that entered meiosis has become four haploid cells.

Results of Meiosis

In male animals, the haploid gametes produced by meiosis are called sperm. In female animals, the haploid gametes produced by meiosis are called eggs.

Mitosis vs. Meiosis

Mitosis results in two genetically identical diploid cells. Mitosis is used for growth. Meiosis results in four genetically different haploid cells. Meiosis is used for gamete production and increased genetic variation.

Debrief…answer the question for your color One: What is the purpose of mitosis and meiosis? Two: What are the steps/stages of mitosis? Three: What is cancer and how is it caused? Four: Describe how DNA changes during the cell cycle.