Sex Cell Production

Meiosis 11-4

Sex cells = Gametes

Egg cell

+

Sperm cell

Where have they been mentioned before?

By the end of this you should know…..

1) What occurs during each stage of meiosis

2) The difference between meiosis and mitosis

Answer me this….

1) How many chromosomes do you have?

2) How many chromosomes do your parents have?

3) How many chromosomes do the egg cell and the sperm cell have?

4) How did they form?

Terms to know:

• Homologous chromosomes - the male AND female parent chromosomes containing the same information – found in diploid cells

• Which set of information is expressed in you? Mom or Dad?

Diploid cells - 2N

Are gametes diploid too?

• Haploid - contain a single set of information (N)

Gamete containing information from one parent

How do we know this?

What is in the circle?

And before that???

• The “father of genetics”, Gregor Mendel used pea plants to show us the same basic ideas that technology has proved to us today

Mendel Vocab you need to know…

Traits = a characteristic that is determined by your genetic information

Genes = sections of DNA that determine your traits

Alleles = the different versions of a gene

Mendel Vocab you need to know…

Traits = eye color

Gene that determines eye color is found here on your chromosome

Now that you are an expert on genetic

vocabulary…

Let’s talk meiosis!!!!!!!!!!!!

How does the process of meiosis produce haploid sex

cells?• 2 Divisions are involved

o Meiosis I - the chromosomes are replicated & homologous chromosomes separated into different cells

o Meiosis II - the sister chromatids are separated from each other

It looks like this…

Meiosis IProphase I*

Metaphase I*

Anaphase I

Telophase I

Cytokinesis

* = makes sex cells unique

In Prophase I…..

• Tetrads line up - chromosomes from mom and dad containing the same information (homologous pairs); contains 4 chromosomes

What happens then?

• Crossing over occurs - portions of homologous chromosomes are exchanged resulting in a new combination of alleles

And during Metaphase I???

• Independent Assortment - tetrads can line up in many different ways allowing for many different combinations of the parents traits to form in the sex cells

Independent Assortment

Meiosis I Review:• Are homologues present at the

end?• Do the cells contain one set or two

sets (one from Mom & one from Dad) of chromosomes at the end?

• So are they haploid or diploid?

Meiosis IINo INTERPHASE!!!

Prophase II

Metaphase II

Anaphase II

Telophase II

Cytokinesis

What other process does this look like?

Meiosis II Review

• What happened to the sister chromatids?

• Are the end cells haploid or diploid?

• Remind me…..why are they called unique?

Check these out….

• http://www.cellsalive.com/meiosis.htm• http://highered.mcgraw-hill.com/sites/

0072495855/student_view0/chapter28/animation__how_meiosis_works.html

Any differences? Egg vs. Sperm?

Meiosis Review:

• How many daughter cells are produced?

• Are they identical to the parents? Why or why not?

• Are the haploid or diploid?

Start your meiosis coloring

Classwork/Homework Meiosis Coloring:

• You will design a meiosis coloring sheet to use as a study guide

• Diploid cells (2n) have green cell membranes; haploid cells (n) have purple cell membranes

• One Side: Interphase & Meiosis I– Divide into 6 boxes (use one box as a key with color codes)– Use pencil first and then color in– Draw 3 homologous pairs (red for maternal chromosomes

and blue for paternal chromosomes)– Label: homologous chromosomes, tetrads, crossing over,

independent assortment, centrioles, spindle fibers, nucleus, sister chromatids

Classwork/Homework Meiosis Coloring:

• Backside: Meiosis II– Divide onto 4 boxes– Use pencil first and then color in– Keep the previous chromosome color and number– Label: centrioles, spindle fibers, nucleus, sister chromatids,

chromosomes

• If complete, they can be used for your meiosis quiz on _______________.