1. DID YOU KNOW? Standard 7, Reproduction of Life TOPIC: MY GOAL:
Open to ISN page
Tues
Standard 7, Reproduction of Life
TOPIC:
MY GOAL:
DID YOU
KNOW?
I will understand the purpose of MEIosis
Formation of sperm takes about a week.
Formation of egg take about years!
Eggs do not go through meiosis 2 until AFTER fertilization!

2. MEIosis
Mitosis

3. Cells divide a SECOND time
MEIOSIS
2 pair of Xsomes
Replication occurs
CROSSING OVER occurs
Cells divide a SECOND time
End up w/ 4 SPERM or EGG w/1/2 # of Xomes as parent cell

4. Why MUST Meiosis take place?
YES!
NO! 23 46 + = 46 92 + =
Sperm + egg = ZYGOTE
n = 23
fetus
Baby
ADULT
2n = 46
n = 23

5. In female Ovary & in male Testis
MEIosis
In female Ovary & in male Testis
Interphase Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Cytokinesis Prophase 2 Metaphase 2 Anaphase 2 Telophase 2
4 strands
So why is there NOT a 2nd Interphase here with Replication?
Produces 4 egg or 4 sperm produced they do NOT continue to divide
2 strands

6. The Xsomes changing places results in a VaRieTy of traits!
ISN p.141
Crossing Over
Metaphase 1
The Xsomes changing places results in a VaRieTy of traits!
Tetrad Crossing Over
From Mom
From Dad

7. Overview of MEIosis Animation

8. Comparison Chart MITOSIS & MEIOSIS
2 cells prod. w/ same # of Xsomes & 1 cell becomes 2
Daughter cells genetically IDENTICAL
2 daughter cells DIPloid
Steps….
NO crossing over!
Creates more of the same cells
Asexual repro.
2 cells result
Cell divides ONCE
Xsome # the SAME
Prod. Somatic cells for growth & repair
# Xsomes cut in ½ & 1 cells becomes 4
Cells prod. genetically diFfErENt
4 HAPloid cells
Steps…
YES crossing over!
Creates Gametes (sex cells) (germ cells)
SEXual – sperm + EGG
4 cells result
Cell divides TWICE
Xsome # reduced by ½
Purpose is to prod. Sperm/Egg for possible future gen.

9. Comparison Chart ISN p.143

10. ISN p.142
Answer 1-7 using the choices below. Some answers are used more than once
Gametes (Egg & Sperm)
Somatic (Body) Cells, like skin, bone, stomach
Zygote
Produced by mitosis
Prod. by meiosis
Prod. by fertilization
Chromosome number in humans is 23
Xsome # in humans is 46
Has diploid # of 23?
Has a HAPloid # of 46?
Does MEIosis produce a zygote?
Text page:161 #2 & #3
Text page 197 #6 B A C A
B and C A
B and C NO

11. Be the change you wish to see in the world
Read over Standard 7 pages in your ISN several times….
There is a Quiz Monday!
HOMEWORK
Be the change you wish to see in the world 11 11