Meiosis Lesson_2010.notebook

1

March 21, 2011

Sep 24­11:21 PM

Aim: Can all cells have 46 chromosomes?

Do Now: How many chromosomes do your body cells usually have?Homework: 809Read pages 46­47

Define the following vocabulary words (in notes and vocabulary section =]sexual reproductionspermegggametefertilizationzygote

diploidhaploidmeiosis

Mar 15­9:38 AM

Sep 24­11:33 PM

Sexual Reproduction

Sep 24­11:36 PM

Egg Sperm

Fertilized Egg

Zygote

Sep 26­1:13 PM

Aim: Why do sex cells have 23 chromosomes?

Do Now: What is a haploid cell?

Sep 29­8:42 AM

Aim: What is meiosis?

Do Now: What is a haploid cell?

What is a diploid cell?

Are sex cells haploid or diploid?Homework:

Read pp.47­ 49Copy the diagram of meiosis 1 and 2 on p. 48 & 49Copy & Answer question 2, 3 on p. 51

Meiosis Lesson_2010.notebook

2

March 21, 2011

Oct 1­11:39 PM

Aim: To model how meiosis makes sex cells

Do Now: Make a chart comparing & contrasting asexual and sexual reproduction

Homework: Study NotesTest Friday 3/25 Mitosis & Meiosis

Mar 18­10:23 AM

Mar 18­10:30 AM Mar 15­10:48 AM

Aim: What is "crossing over" in meiosis?

Do Now: What is the most important phase of meiosis?

Homework: Due Friday

Vocab: Homologous chromosomes, haploid, diploid, gamete, zygote, fertilization, autosomes

Read pp.247­249 p.249 #1­4

Read pp 250­254p.254 # 1­4

LE 1LE33/15/2011

Mar 15­11:04 AM Sep 29­8:54 AM

MeiosisPurpose: To generate genetic diversity

How is this done?Through "crossing over " of genetic material of chromosomes during reproduction of sex cells (gametes)

Crossing Over­ when genes change places on complementary chromosomes (also known as homologous chromosomes)

­Occurs in Prophase 1 stage of meiosis&

only in Sex Cells (Sperm & Egg cells!)

m

­the process by which sex cells are made

When and where does it happen?

LE 1 3/15/11

Meiosis Lesson_2010.notebook

3

March 21, 2011

Sep 29­12:32 PM Sep 29­1:06 PM

Process of Meiosis

Homologous Chromosomes: A pair of chromosomes having the same Gene sequences, each derived from one parent

Example: two chromosomes have genes coding for eye color: One may code for brown eyes, the other for blue. One of them may be dominant and the other recessive . An individual has genes for brown eyes and blue eyes, only one eye color is expressed

A gene is a piece of a chromosome that codes for a trait.Genes are made up of DNA

1. Homologous Chromosomes pair up2. These pairs duplicate & sometimes crossover, exchanging genes in the process3. The cell splits into two cells with 46 chromosomes each (End of Meiosis I)4. These cells continue to pull apart, forming 4 new daughter cells5. Each daughter cell has 23 chromosomes (End of Meiosis II). These are the newly formed sex cells­ sperm & eggs

Sep 29­2:04 PM Sep 29­2:04 PM

Oct 1­11:04 PM

Prophase I Crossing Over takes place

LE 1 3/15/11

Mar 15­9:48 AM

Meiosis Lesson_2010.notebook

4

March 21, 2011

Mar 15­9:48 AM

Stages of MeiosisMitosis­PMAT ­2 daughter cells

­occurs in somatic (body) cells

Meiosis: Meiosis I ­Prophase I

­Metaphase I­Anaphase I

­Telophase I(2 cells/ 46 chrom)

Meiosis IIP II

M II

A II

T II

mostimportant

4 daughter cells/ 23 chromosomes each(Division Reduction)

23 23 23 2346 46

LE 3 3/15/11

Sep 29­12:39 PM

During the first stage of meiosis, an unusual ­ and vitally important ­ event occurs: Crossing Over.

During Prophase of Meiosis I, homologous chromosomes in the cell:

• Pair up alongside each other lengthwise, and• Swap bits and pieces of their chromosomes, • shuffling the genome! • Crossing Over ONLY happens in Prophase of Meiosis I, and • results in: • NEW genetic combinations that did not exist before in the parent. • Soon after, the Homologues separate, never to see each other again....• the new chromosomes become part of eggs and sperm that will be .....• genetically unique to each other and to their parent!!

Crossing Over

Sep 24­11:42 PM Sep 24­11:43 PM

What cells cannot have 46 chromosomes?Egg and Sperm cells

Sep 24­11:47 PM

Meiosis ­ the process by which sex cells reproduce themselves

Sep 24­11:50 PM

http://www.stolaf.edu/people/giannini/flashanimat/celldivision/meiosis.swf

Meiosis Lesson_2010.notebook

5

March 21, 2011

Sep 24­11:50 PM

Prophase II

Sep 24­11:58 PM

Sep 24­11:59 PM

Meiosis II

Produces 4 egg cells or 4 sperm cellsEgg & Sperm Cells have 23 chromosomes each

Sep 25­12:23 AM

Mar 18­8:04 AM

Aim: What occurs if meisosis goes wrong?

Do Now: 1. An organism has 58 chromosomes in a somatic cell. ­ What is the diploid # of chromosomes ­ What is the haploid #? ­ How many chromosomes at the end the S1 phase?

LE1 & 3 Homework:Read pp. 256­ 257p. 258 # 1­4

Test on Chap 10 & 11 next Wednesday

Mar 18­8:04 AM

Aim: What occurs if meisosis goes wrong?

Do Now: 1. An organism has 58 chromosomes in a somatic cell. ­ What is the diploid # of chromosomes ­ What is the haploid #? ­ How many chromosomes at the end the S1 phase?

LE1 & 3 Homework:Read pp. 256­ 257p. 258 # 1­4

Test on Chap 10 & 11 next Wednesday

Meiosis Lesson_2010.notebook

6

March 21, 2011

Sep 25­12:25 AM

Meiosis is not flawless!It is estimated that from 10-20% of all human fertilized eggs contain chromosome abnormalitiesThese are the most common cause of pregnancy failure (35% of the cases).

Chromosome abnormalities:• arise from errors in meiosis, usally meiosis I; • occur more often (90%) during egg formation than during sperm formation; • become more frequent as a woman ages (egg cells are older!)• Aneuploidy­ the gain or loss of whole chromosomes is the most common chromosome abnormality. ­ caused by nondisjunction, the failure of chromosomes to correctly separate: either as homologues during meiosis I or sister chromatids during meiosis IIExamples: • Monosomy­ Zygotes missing one chromosome, cannot develop to birth (except for females with a single X chromosome). • Trisomy­ Three of the same chromosome is also lethal except for chromosomes 13, 18, and 21 ­(trisomy 21 is the cause of Down syndrome • Three or more X chromosomes are viable because all but one of them are inactivated.

Mar 18­8:18 AM

Aim: What is asexual & sexual reproduction of organisms?Do Now: Do all organisms need a partner to reproduce? Why do some organisms need a partner to reproduce?

Study for test Wednesday: Chap 10 & 11Friday 3/25

LE 1 3/21/2011LE 3

Mar 18­8:22 AM

Meisosis Mitosis Review1. Describe the purpose of mitosis __________________________________________________2. How many times does the cell divide during mitosis? _________________________________3. What kind of cells are produced at the end of mitosis? _________________________________4. What are sister chromatids? _____________________________________________________5. Briefly describe what happens during prophase ______________________________________6. Draw and label picture of what a cell looks like during prophase. Draw on the back of page.7. Briefly describe what happens during metaphase _____________________________________8. Draw and label a picture of what a cell looks like during metaphase. Draw on the back of page.9. Briefly describe what happens during anaphase _____________________________________10. Draw and label a picture of what a cell looks like during anaphase. Draw on the back of page.11. Briefly describe what happens during telophase _____________________________________12. Draw and label a picture of what a cell looks like during telophase. Draw on the back of page.13. Is cytokinesis part of mitosis ____________________________________________________14. Briefly describe what happens during cytokinesis ____________________________________15. Draw a picture of what a cell looks like during cytokinesis. Draw on the back of page.16. Describe the purpose of meiosis __________________________________________________17. How many times does the cell divide during Meiosis? _________________________________18. What kind of cells are produced at the end of meiosis? ________________________________19. Briefly describe the difference of prophase I & II. ____________________________________20. Draw and label a picture of prophase I & II. Draw on the back of page.21. Briefly describe the difference of metaphase I & II. ___________________________________22. Draw and label a picture of metaphase I & II. Draw on the back of page.23. Briefly describe the difference of anaphase I & II. ____________________________________24. Draw and label a picture of anaphase I & II. Draw on the back of page.25. Briefly describe the difference of telophase I & II. ____________________________________26. Draw and label a picture of telophase I & II. Draw on the back of page.27. What would happen to cell division if a chemical was put in the cell that did not allow for cell division to occur?

Mar 21­1:42 PM