Unit 3 Cells and Photosynthesis Section 5 Meiosis Access Biology

Cells and Photosynthesis Vocabulary Cells Mitosis Meiosis Animal Cells and Structures Plant Cells and Structures Photosynthesis Cellular Respiration

Standards SC.912.L.16.17 Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their consequences for genetic variation. SC.912.L.16.Su.6 Recognize that cells reproduce by dividing. SC.912.L.16.Pa.6 Recognize that living things produce offspring (reproduce). SC.912.L.16.16 Describe the process of meiosis, including independent assortment and crossing over. Explain how reduction division results in the formation of haploid gametes or spores. SC.912.L.16.In.7 Recognize that cells reproduce by dividing to produce new cells that are identical (mitosis) or new cells that are different (meiosis). SC.912.L.18.Pa.3 Identify that food is a source of energy.

Essential Questions/Big Ideas What is meiosis? What are the different phases?

Learn more about Meiosis, click on image…

What is meiosis?

Meisosis Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells – sperm in males, eggs in females.

Watch as the cell prepares as it does for mitosis before the DNA condenses and matching pairs of chromosomes from the mother and father find each other

Stages of Meiosis Meiosis can be divided into eight stages. These are divided between the first time the cell divides (meiosis I) and the second time it divides (meiosis II) This Photo by Unknown Author is licensed under CC BY-SA

Stages of Meiosis

Animation of Meiosis, click image to play…

Meiosis I and II Interphase The DNA in the cell is copied resulting in two identical full sets of chromosomes. During interphase, microtubules extend from these centrosomes. Meiosis I and II Interphase

Meiosis I and II Prophase The copied chromosomes condense into X-shaped structures that can be easily seen under a microscope. The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on. Prophase I is where crossing over occurs and this the variation of genetic material. At the end of Prophase the membrane around the nucleus in the cell dissolves away, releasing the chromosomes.

Meiosis I and II Metaphase The chromosome pairs line up next to each other along the center (equator) of the cell. The meiotic spindle fibers attach to one chromosome of each pair.

Meiosis I and II Anaphase The pair of chromosomes are then pulled apart by the meiotic spindle, which pulls one chromosome to one pole of the cell and the other chromosome to the opposite pole.

Meiosis I and II Telophase, cytokinesis The chromosomes complete their move to the opposite poles of the cell. A membrane forms around each set of chromosomes to create two new nuclei.

Match the image and phase meiosis I prophase I metaphase I anaphase I telophase I meiosis II metaphase II prophase II telophase II anaphase II

Mitosis compared to Meiosis Click on image to play

What have you learned… Click on image to start link