Meiosis and its role in sexual reproduction Themes: Organization Unity and Diversity

Meiosis Learning Objectives: See how meiosis and sexual reproduction can increase genetic variation (shuffle mutations). Describe how the process of meiosis produces haploid cells. Compare meiosis to mitosis. Follow-up Activity: Karyotype—Determine how chromosomes are organized and what we can determine from looking at homologous pairs.

Meiosis Cell Division that results in daughter cells receiving half the number of chromosomes (reduction division) Somatic cell (body cell) – Diploid (2N) Gametes (sperm/ovum)- Haploid (n) * If any of these issues caused a schedule delay or need to be discussed further, include details in next slide.

3 ways meiosis allows for genetic change Meiosis shuffles mutation through: Independent assortment of chromosomes Crossing over Random fertilization

Independent assortment

Crossing over

Random Fertilization

Animations on Meiosis We’ll use this video to stop and identify the organization of the process. How many time does interphase occur? What happens during meiosis I? What happens during meiosis II? Describe the result of meiosis?

Meiosis Two phases : Meiosis I and Meiosis II Meiosis I Goal of this phase is to create variation by crossing over between homologous chromosomes. Sister chromatids are not separated during anaphase, but whole homologous chromosomes are separated.

Meiosis No DNA replication between Meiosis I and Meiosis II Meiosis II Sister chromatids of each homologous chromosome gets separated. 4 daughter nuclei is formed.

Haploid vs. Diploid Different organisms have a different number of chromosomes that make up one set - (n) Organism Body Cell Gamete Human 23 Sweet Pea 7 Fruitfly 4 How come we have 46 chromosomes in our body cells if the gametes (sperm and egg cells have only 23)

Homologous Chromosomes Chromosomes identical in size and staining patterns and have the same genes One is inherited from father and one from the mother.

In the human body, this process forms sperm and egg (more detail next class!)

Sexual reproduction causes the cells to become Diploid again

Exit Slip Funny square dancing video:http://www.youtube.com/watch?v=JKXAdwCibsA&feature=endscreen&NR=1 Watch the video and answer the exit slip questions.