Meiosis I and II - Formation of Egg and Sperm

Friday we had our DQQ and then I let you guys watch some podcasts on weird science that deals with this chapter.  (Like conjoined twins, 6 legged cows, 2 faced pigs and 2 headed snakes)
Today on the other hand... back to routine

Monday February 25^th

*Meiosis II is similar to mitosis in the fact that during metaphase and anaphase Sister Chromatids line up and separate from each other.

*At the end of meiosis II we now have 4 cells that are considered Haploid because each has One set of DNA

*True or False: Each of the resulting cells are identical.

Which statement BEST describes how endocytosis differs from diffusion?

A. Unlike diffusion, endocytosis requires energy

B Unlike diffusion, endocytosis focuses on small particles

C. Unlike diffusion, endocytosis allows substances to enter a cell

D. Unlike diffusion, endocytosis relies on the structure of a cell wall.

After this we walked through meiosis I and II using the magnet boards.  See the pics and descriptions below.

We would first start with a cell with unreplicated DNA

During the S phase of interphase
the DNA would replicate. Now all the
chromosomes are duplicated with identical
sister chromatids

During phrophase 1 the homologous chromosomes pair up with each other (blue from dad, red from mom)

And crossing over may occur. During crossing over the DNA from one chromosomes may "swap" with the DNA of its homolog.

Making for chromosomes with combinations of both maternal and paternal DNA

During Metaphase I Homologous
Chromosomes line up at the equator (middle)

Durin Anaphase I these Homologous
chromosomes then pull apart from each other

Now we have TWO cells with a different combination
of the father and mothers DNA

During Metaphase, each cell will now have
the sister chromatids move the middle of each
cell.

During anaphase those sister chromatids will now pull apart from each other.

At the end of Telophase II we have four
genetically different gametes with ONE set
of chromosomes each.  Each of these
has a different combination of the person's maternal
and paternal DNA

We then wrote down some differences between sperm and egg production.

Here were some ways I showed you the difference between egg and sperm development

When eggs form, three small polar bodies are created which will
die off and only One will become an egg.  It needs to be much larger
because it will carry all the cytoplasm an organelles for the zygote

Sperm on the other hand split evenly during meiosis I and II
creating 4 fairly small cells which will then develop
tails in order to "swim" towards the egg.

During fertilization, a sperm will break through the cell
membrane of an egg resulting in a diploid gamete.

Finally, I had you watch the following video on Ligers which we will discuss a little more how this can happen and how it relates to what we are talking about now!