1. Tuesday January 29th, 2019 Interphase Prophase Metaphase Anaphase
Do Now
List the stage of mitosis the following onion cells are in:
Interphase
Prophase
Metaphase
Anaphase
Telophase

2. Interphase:
4, 5, 6, 8, 11,
12, 13, 14, 16,
19, 20, & 22
Prophase:
2, 15 & 21
Metaphase:
1, 10, & 17
Anaphase:
7 & 18
Telophase:
3 & 9

3. The cell division of love (and diversity) <3
Meiosis
The cell division of love (and diversity) <3
EQ: How does the sorting and recombination of genes in sexual reproduction result in variety of gene combinations?

4. Homologous Chromosomes vs. Sister Chromatids
two chromosomes (one from your father, one from your mother)
that have the same genes, length, & appearance
Divided during meiosis I
Sister Chromatids:
halves of the same chromosome
The duplicated sides that remain attached at the centromere
Divided during meiosis II
sister
chromatids
sister
chromatids
Label your diagram in your notes

5. Chromosomes
Autosomes: chromosomes that contain genes for characteristics NOT directly related to the sex of an organism
Chromosome pairs 1-22 in humans
Sex Chromosomes: directly control the development of sexual characteristics
Pair 23 – in mammals, the X and Y chromosomes determine gender
Female = X X
Male = X Y

6. Sex Chromosomes The X chromosome is the larger sex chromosome
Also contains genes that have nothing to do with sexual characteristics
The Y chromosome is the smallest chromosome
Carries the fewest genes
The genes on this chromosome direct the development of testes and other male traits

7. Karyotype

8. Types of Cells Somatic Cells: (body cells) Gametes: (sex cells)
Contain normal number of chromosomes (46)
Diploid (2 sets of each)
Ex. skin cells, liver cells
Mitosis
Gametes: (sex cells)
Contain half the number of chromosomes (23)
Haploid (1 set of each)
Ex. eggs (female) and sperm (male)
Meiosis

9. Gametes
(Sex Cells)
Somatic Cells
(Body Cells)

10. Gametes are haploids, Which means?
Sex cells have half the chromosomes as somatic cells.
Think/Pair/Share
How do you think they get to have half the number of chromosomes?

11. Benefits of Sexual Reproduction
Sexual Reproduction- two gametes fuse during fertilization and the offspring are a genetic mixture of both parents
Benefits of Sexual Reproduction
Allows genetic variation- differences in appearances that offspring show from their parents.
Ability to adapt to environmental changes

12. Fertilization is the fusion of an egg and sperm
Fertilization is the fusion of an egg and sperm - restores correct chromosome number
Somatic cells
Meiosis
Fertilization
Gametes

13. Steps of Meiosis Interphase I Meiosis I Prophase I : Crossing Over
G1, S, G2
Cell growth and DNA rep.
Meiosis I
Prophase I : Crossing Over
Metaphase I: Independent assortment
Anaphase I
Telophase I
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Students are not writing this page down.

14. Stop and Think What happens FIRST in both mitosis & meiosis?
Interphase
What happens during interphase?

15. Meiosis I – Overview
DNA rep during interphase

16. Meiosis 1 Main points: Interphase occurs = DNA replication
Crossing over occurs = exchange of genetic material
Homologous chromosomes separate
Results in 2 diploid daughter cells

17. Prophase I Homologous chromosomes pair up Nuclear membrane breaks down
Crossing over occurs – exchanging of segments
Creates new combinations

18. Metaphase I
Homologous chromosomes align along the cell equator or middle of the cell
each side has a chromosome from each parent
Independent assortment occurs – random alignments of homologous chromosomes
Adds to genetic variation

19. Independent Assortment

20. Anaphase I
The paired chromosomes split and move towards opposite poles
sister chromatids are still attached

21. Telophase I Spindle fibers fall apart Nuclear membrane reforms
2 nuclei

22. Cytokinesis Two diploid cells are produced
How many chromosomes are in a diploid cell? 46
What is cytokinesis?
Division of cell’s cytoplasm to create two new cells

23. Meiosis II
No DNA rep

24. Meiosis II Main Points: No interphase = no DNA replication
Sister chromatids separate
Results in 4 genetically different, haploid gametes (n)

25. Prophase II Centrioles more to opposites sides
Nuclear envelope breaks down

26. Metaphase II
Spindle fibers align chromosomes along the metaphase plate (middle)

27. Anaphase II
Sister chromatids are pulled apart towards opposite sides of the cell by centrioles

28. Telophase II
Spindle fibers fall apart
Nuclear membrane forms

29. Cytokinesis Produces 4 haploid gametes
Each gamete is genetically unique
What is cytokinesis?
Division of the cells cytoplasm to create two new cells

30. Putting it all together…
meiosis  fertilization  mitosis + development
gametes 46 23 46 23 46 46 46 46 46 23
meiosis 46 46
egg 46 46 23
zygote
fertilization
mitosis & development
mitosis
sperm

31. The value of meiosis 1 Consistency over time
meiosis keeps chromosome number same from generation to generation
Mom
from Mom
Consider the greater variation with 23 pairs of chromosomes = mixing and matching
Dad
offspring
from Dad

32. new gametes made by offspring
The value of meiosis 2
Change over time
meiosis introduces genetic variation
gametes of offspring do not have same genes as gametes from parents
new combinations of traits
new gametes made by offspring
Consider the greater variation with 23 pairs of chromosomes = mixing and matching
from Dad
variation
from Mom
offspring

33. Meiosis Results – reduction division
Four haploid daughter cells called gametes
Eggs
Sperm
Each cell is unique from one another (and parent)
***Move to before sexual reproduction
Why is it called a reduction division?
1 cell divides into 4 cells
The 4 new cells have a reduced number of chromosomes (haploid = half)

34. The whole Process

36. Gummy Worm Lab
Use the lab instructions as well as the diagram in the book and the diagram in your notes to model the process of Meiosis using the candy provided to you. This is an explorative lab. You are responsible for reading and checking yourself as you go.
Reminder:
Nuclear Envelope – String
Spindle Fibers – String Candy (Twizzler)
Centrioles – M&Ms
Chromosomes – Gummy Worms
Centromere – Tooth Pick
Cell – Paper Towel

37. Exit ticket
Clear desk of everything except DO NOW and something to write with

38. Mitosis and meiosis are processes involved in cellular reproduction
Mitosis and meiosis are processes involved in cellular reproduction. Which of the following describes and event that results from mitosis but NOT meiosis?
A. two stages of cell division
B. replication of cellular genetic material
C. daughter cells that are identical to the parent cell
D. four daughter cells that are produced from each parent cell

39. 2. Which type of reproduction leads to increased genetic variation on a population?
A. Parthenogenesis
B. asexual reproduction
C. Sexual reproduction
D. Vegetative reproduction

40. The diagram below shows homologous chromosomes during prophase I of meiosis. Which of the following correctly describes the process being illustrated? A. mutation in which the DNA content of the gene is altered B. segregation of sister chromatids C. condensation and segregation of alleles D. crossing-over in which alleles are exchanged

41. The diagram shows a cellular process that occurs in organisms
The diagram shows a cellular process that occurs in organisms. What is the name of this process? 
A. meiosis
B. mitosis
C. endocytosis
D. phagocytosis