Nondisjunction

Tuesday February 26^th

At the end of meiosis we have created 4 haploid gametes, in males these are known as Sperm in females these are known as Eggs

If a female gamete and a male gamete combined, how many chromosomes would the resulting cell have? 46 which would be haploid or diploid?

During meiosis 1 homologous chromosomes separate from each other.  If this did not happen with one of the pairs and then meiosis went on as normal what would the resulting gametes look like?

The result would be two of the gametes having an extra chromosome and the other two gametes missing a chromosome.  

After going through the daily questions and using your magnetic chromosomes, we moved into notes on this specific abnormality known as nondisjunction - For an online tutorial on this check out the following link http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/

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!

Meiosis Day 2

Thursday February 21^st

During meiosis 1, what pairs up in the nucleus? Homologous Chromosomes (It is important that you know it's the homologous chromosomes and not JUST chromosomes.  Chromosomes line up during Mitosis - but during meiosis this first step of homologous chromosomes pairing is VERY important!!!)

During this time, the legs of chromosomes can swap DNA in a process known as Crossing Over. (keep in mind, this is not what we would call a mutation because it is swapping DNA from the same section of a chromosome.  It just results in some of your moms dna being found on your dads chromosome.)

In order for meiosis to create four, genetcially different gametes, DNA replication must occur.  Which of these best describes when DNA replication would occur during meiosis?

A.  Interphase of meiosis I                 

B.  Anaphase I in meiosis I      

C. Interphase in meiosis II  

D.  Anaphase II in meiosis II

DNA replication will ALWAYS occur before mitosis OR meiosis begins

Which statement BEST describes the relationship between an allele and a gene?

A.  An allele is a variation of a gene that can be expressed as a phenotype.

B.  An allele is the part of a gene that attaches to messenger RNA molecules

C.  An allele is a segment of a DNA molecule that controls replication of a gene

D.  An allele is the primary protein made by a gene found in a developing embryo.

We spent the rest of the period walking through meiosis I and II using our magnet boards and clay models.

Prophase 1 - Homologous chromosomes pair up with each other

then you guys made some of your own
chromosomes with clay so I could show you
crossing over

Sometimes the legs of homologous chromosomes will "cross over"
each other

The DNA is swapped on those sections so know the sister
chromatids are no longer identical

During Metaphase 1 these homologous chromosomes
will line up in the middle of the cell

During AnaphaseI then these homologous chromosomes Pull
apart from each other.

During Telophase I the nuclear envelop closes back in and
now you have two cell with different combinations of
the mothers and fathers DNA

 Meiosis II involved cutting apart the chromosomes which is what we spent the rest of the period doing.  Catch more pics of meisosis II tomorrow! (AFTER our DQQ!!)

Meiosis 1 day 1

Wednesday February 20^th

1.The allele for having a widows peak (W) is dominant over the allele for having a straight hairline(w).  If someone had the following genotype, Ww, what kind of hair line do they have?
They would have a widows peak.  What I gave you was a Genotype (which is the set of alleles for a trait)  Since there is a dominant allele (W) then it doesn't matter what the second allele is, because it is dominant, that is what is expressed.  When you told me that they would have a widows peak, you were telling me there Phenotype.  These were all new terms that we discussed yesterday.  I then had you look at your magnet boards at homologous chromosomes and you told me the genotypes of different genes.  This then led to the second question.

2. Which allele will they be more likely to pass on to their offspring?
there will be an equal chance of passing either the Dominant (W) or the recessive (w) on to their offspring.  These alleles are randomly segregated during meiosis. 

3.  During what process will this be determined?
Meiosis.   We will continue to use these magnet boards to see how the alleles get distributed among gametes. 

KQOD.  Which statement best explains why large changes in pH can affect the functions of plant enzymes?

Large changes in pH increase the rate of cellular chemical reactions

B.  Large changes in pH provide the energy necessary to activate an enzyme

C.  Large changes in pH can denature an enzyme causing a change in its shape

D.  Large changes in pH cn cause an enzye to react with a different substrate
This question was not only about the function of enzymes, but how pH and temperature affect enzyme activity.  Many of you picked A or B - these both describe the FUNCTION of enzymes - but the question was about how large changes in pH will affect the enzyme.  Large changes in pH or temperature will change the shape of an enzyme.  Recall that we learned enzymes are proteins and they are dependent on the shape.
After these we started into the first part of meiosis.  Using our magnet boards we put the cell at least into prophase 1 and metaphase 1.  We also discussed all the different factors that contribute to genetic diversity at this point.

During Prophase 1homologous chromosomes
pair up

During Metaphase 1 the homologous chromosomes line up in the center of the cell independently.  (not all of your
moms on one side and your dads on the other.)

Today's daily questions and notes

Tuesday February 19th

A mosquito has 16 chromosomes in each somatic cell, how many chromosomes would be found in a mosquito’s gametes?
8 - Recall that gametes are HAPLOID cells and Somatic cells (normal body cells) are DIPLOID.  Haploid cells contain only ONE set of chromosomes while Diploid cells contain two sets (one from each parent).  If you are given the number of diploid chromosomes, you would divide that by 2 in order to determine the number of chromosomes in an organisms gametes.
The next question uses the same logic only in reverse. A frog’s haploid cells contain 13 chromosomes, how many chromosomes would be found in its somatic cells?
26

Which of the following explains why asexually reproducing organisms are more likely to go extinct when their environment changes?

1.  They reproduce without DNA

2.  They only reproduce in small numbers

3.  They lack a variety of genetic combinations.
 Remember, in asexuallly reproducing organisms all the offspring are genetically identical to the parent.  Because of this lack of variation if an environmental change wipes out one, it will wipe them ALL out!!

4.  They are easier for predators to capture

Keystone QOD

Which feature is common to all prokaryotic and eukaryotic organisms?

1.  Endoplasmic reticulum that stores fat reserves

2.  Ribosomes that produce complex carbohydrates (This was ALMOST correct, prokaryotic and eukaryotic cells both have Ribosomes. What made this answer incorrect was that ribosomes do not produce complex carbohydrates, they produce proteins.)

3.  Nucleic acids that code for genetic characteristics

4.  Mitochondria that are sites for cellular respiration

Today's notes got us a little closer to the steps of meiosis - Stay tuned for that!!

Strawberry DNA Extraction Lab

Thursday we had the chance to do some "fun" science and extracted DNA from strawberries. Here are some pics and descriptions of what we did.

First we need some strawberries



Then we went through Strawberry DESTRUCTION!!!

We added DNA Extraction Buffer then demolished it again




Let it go through a filter into the test tube



Next was adding Rubbing alcohol to separate out the DNA

The DNA is the white "stringy" stuff that you see in the
alcohol portion of the test tube

Then we tried carefully to spool some of that DNA out
of the test tube! 



A days worth of DNA!

Last weeks Daily Questions and Notes

Well, the last time i have posted was over a WEEK ago!  Sorry about that guys!!  Here were the daily questions from last week and the notes we made it through.  Thursday we had our "real science" day and extracted DNA from strawberries.  Check out the next post with pics from that!!

Monday February 11^th

Each one of the somatic cells (our body cells) has how many chromosomes?

 46

Where did those chromosomes come from.

 23 from your mother, 23 from your father.

We will be working with these chromosome models through this chapter.
In this "cell" there are 46 chromosomes.  All the blue ones are the 23 that we received from our fathers and the 23 red ones are those we received from our mothers.

What two cells (from your parents) came together in order to give you the unique combination of DNA that you have?

 Egg and Sperm

How many chromosomes did each of THOSE cells HAVE to have?

23

                                         Tuesday February 12^th 

In asexual reproduction, how many parents contribute genetic information to the offspring?

One

How are the offspring related to the parent?

They are genetically identical (Clones)

In Sexual reproduction how many parents contribute genetic information to the offspring?

Two

How are the offspring related to the parents?

They are a combination of both parents DNA

Sexually reproducing organisms have sets of chromosomes known as Homologous chromosomes.

Wednesday February 13^th

*Which type of reproduction provides more genetic diversity sexual or asexual reproduction?
Sexual.  In sexual reproduction there are two parents that contribute DNA to the offspring.  Because of this all the offspring will be slightly different (with the exception of identical twins) and the offpsring will all be a different combination of their parents DNA.

*Sexual reproducing organisms contain cells that have TWO sets of Chromosomes (homologous Chromosomes).  What is the name of these types of CELLS? Diploid.  Di= 2

*How many sets of chromosomes are found in our sex cells? One - they are HAPLOID

Keystone QOD
Increased exercise can lead to an increased number of mitochondria in the skeletal muscle cells.  Which of the following BEST describes the aspect of increased exercise that leads to this change?

A.  Increased requirement of energy for immediate use

B.  decreased supply of energy in long-term storage form

C.   decreased time span for maintenance of recently stored energy

D.  increased volume requirements for storing energy in stable form.
This question was really about the role of mitochondria.  Remember, mitochondria are the organelles in our cells that produce ATP (our molecule of energy)  So the question really was assessing if you know the role of the mitochondria.

Notes From last week