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The production of SEX cells

Brooke Wilks

on 18 November 2016

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Transcript of Meiosis

Types of Reproduction
Organisms can reproduce in 2 ways
Sex Cells
Humans have 46 chromosomes (23 pairs) in each body cell.
Results of Meiosis
Meiosis is a....
Special form of cell division that creates haploid gametes
* 4 haploid cells (1n) each with a unique genetic make up.
*Body cells are called SOMATIC cells
How sex cells are made...
Asexual: When DNA is contributed by 1 parent
*Produces offspring that are genetically identical.(No variation)
Sexual reproduction: When DNA is contributed by 2 parents.
* Results in genetic variation in offspring
* Results in a new combination of genes
* Includes a special form of cell division called meiosis
* Somatic cells have 2 complete sets of chromosomes
*These are diploid cells (2n)
Sex cells are called gametes. (name male & female gametes)
Contain only one set of chromosomes (23)
These are called haploid (1n)
When they combine the result is 46 chromosomes
Non-disjunction: Failure of homologous chromosomes or sister chromatids to separate during division
Trisomy 21
Klinefelter XXY
Turner X_
2) The cell divides twice but DNA is only copied once
3) Meiosis results in cells with 1 set of chromosomes rather than 2
1) Starts with diploid cells
How many chromosomes do diploid cells have? how would abbreviate it?
Males: all 4 cells become sperm
Females: only 1 becomes an egg.
Eggs are so large they require more cytoplasm. 3 smaller cells with less cytoplasm will die. These are called polar bodies
Produces somatic cells
Daughter cells are diploid
Two daughter cells are produced
In metaphase chromosomes line up by themselves
One nuclear division
Produces cells for growth and repair
Daughter cells have 2 sets of chromosomes (pairs)
Daughter cells are genetically identical to the parent cell
All daughter cells are genetically identical
Produces Gametes (___ cells)
Daughter cells are haploid (_n)
4 daughter cells are produced
In metaphase I chromosomes line up in pairs
2 Nuclear divisions
Produces cells for reproduction
Daughter cells have only one copy of a pair the chromosome pairs
Daughter cells have half of the genes from the parent cells
Genetic diversity through crossing over and random separation
How this works!
There are 2 stages of meiosis
Meiosis I and meiosis II
Prophase I-
homologous chromosomes (tetrads) align

There are 4 sister chromatids

These chromatids connect and trade sections of their chromosomes.

Metaphase I-
Spindle fibers attach to centromeres
Homologous chromosomes align at the cellular equator
Anaphase I
homologous chromosomes pull apart and go to the poles of the cell
Meiosis II
Telophase I
Chromosomes arrive at the poles
Nuclear membrane reforms
Prophase II
More spindle fibers form
Centrioles go to the poles of the cell
Metaphase II
Chromosomes align at the cellular equator
Anaphase II
Chromatids separate and begin to move to the poles
Telophase II
Chromatids arrive at the poles
Nuclear membrane reforms
*This is called crossing over!
Cytoplasm divides
Proteins contract forming a cleavage furrow
Meiosis I
Cytokinesis: Cytoplasm divides and forms haploid sex cells
46 chromosomes


Imagine you are a plant and there is a drought. You are about to die. Discuss which type of reproduction would result in offspring that might survive better than you.

How will you remember what diploid means?

What does somatic mean?

What are some examples of somatic cells?
Stop and Talk
How will you remember what haploid means?

What is the difference between somatic cells and gametic cells? List ALL differences you can think of.
What are these called when they are in pairs?
What are these?
What pulls homologous chromosomes apart?
Answer the following questions
Why is one chromosome 2 different colors? hint: you may need to look at meiosis I notes.

Are these cells haploid or diploid? how do you know?
Write down the definition of diploid AND somatic in the needed vocabulary in your notes
Stop and Talk
Write down the definition of haploid AND gametic in the needed vocabulary in your notes
In mitosis duplicated chromosomes are split apart and the sister chromatids go to the poles.

How is meiosis one different from mitosis?
What stage is this?
How is meiosis II like mitosis?
How is it different?
Unit 8: Meiosis and Karyotype
Fun Fact Friday!

1. No bellwork for this unit
a. Unit is only 7 days and is split into 2 parts.

2. Part 1: Meiosis- Summative Quiz On Tuesday.

3. Part 2: Karyotypes and chromosome mutations- Formative quiz on Friday.
I will practice meiosis


Playing quizziz AND drawing stages of meiosis


1. Finish Video

2. Quiz Tomorrow (first thing!)

2nd hour

1) Mutations and Karyotype Notes


3rd and 4th
1) Karyotypes and Chromosome Mutation Notes
2) Vocab Word Wall
Agenda Pre-AP

1)Karyotypes and Chromosome mutations
Full transcript