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)
o
Somatic cell (body cell) – Diploid (2N)
o
Gametes (sperm/ovum)- Haploid (n)
3 ways meiosis allows for genetic change
•
Meiosis shuffles mutation through:
o
Independent assortment of chromosomes
o
Crossing over
o
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=e
ndscreen&NR=1
•
Watch the video and answer the exit slip questions.