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AP Biology
Chapter 13 Guided Reading Assignment

1.
Compare and contrast asexual and sexual reproduction.

Asexual reproduction: a single organism is the parent and passes copies of all its genes to its offspring.
  • For example, a single-celled eykaryotic organism can reproduce by mitotic cell division (DNA is copied and separated equally between 2 daughter cells. The offspring have exact copies of the parent's genome.

Sexual Reproduction: two parents have an offspring that have unique combination of genes inherited from the two parents. The offspring vary genetically from their siblings and both parents. They are variations; genetic variations are important.
external image ciliate.gif
-Fernanda R. Ashley A


2.
Define the following terms:

a.
Life cycle
Generation to generation sequence of all the different stages in the reproductive history of an organism, including: an organism from conception to the reproduction of own offspring.
cellcycle.gif

b.
Somatic cell
Include any cell other than a gamete; Human somatic cells has 46 chromosomes.
somatic.jpg

c.
Karyotype
The display of chromosomes in Homologous pairs starting with the longest chromosomes moving to the shortest.
karyotype.gif

d.
Homologous chromosomes
The two chromosomes that compose a pair of the same length, centromere position, and staining pattern.

Homologous_chromosomes.GIF

e.
Sex chromosomes
The X and Y chromosomes; they help determine the sex of an individual.
external image chromosomes.jpg

f.
Autosomes
All chromosomes other than the x and y chromosomes




autosome.gif


g.
Diploid cell
All cells within the body other than sex cell. These cells contain two copies of each chromosomes, one from the mother and one from the father.
diploid.jpg


h.
Haploid cell
A single complete set of chromosomes. (N=23 for humans)
external image chromosomes.gif

i.
Fertilization- The union of haploid gametes to produce a diploid zygote.

external image 06%20fertilization.jpg This picture shows sperm cells are trying to unionize with a egg cell.

j.
Zygote- The diploid product of the union of haploid gametes in conception. Or a fertilized egg.


external image images?q=tbn:ANd9GcR4ihBHJFehaTHWbZoRoRRVElGFDmOLrKV8lqtyn3bVGf8W1UXA&t=1


k.
Meiosis - A two-stage type of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell.

meiosis-big.gif This picture shows the two stages of meiotic division.
-Mike G.





3.
How are karyotypes prepared?

Karyotypes are prepared by isolated somatic cells, which are treated with a drugs to stimulate mitosis and then grown in culture for several days. Then the slide of cells is then stained in metaphase and viewed under a microscope with a special digital camera. In English, cells that do not include gametes are treated with a certain drug and left for a couple days to sit and grow. Then, the slide of cells that was growing is stained when the cells are in the process stage of metaphase. This staining allows for them to become visible under a microscope with a unique digital camera made just for karyotyping. This allows scientists to form karyotypes from looking at the chromosomes during metaphase in mitosis.

Karyotypes.gifBad_Karyotype.jpg

These are both examples of karyotypes. The karyotype on the left is a normal looking karyotype with no difficiencies. The karyotype on the right, however, has MULTIPLE difficiencies that probably isn't even possible to have...
Karyotype videos
Brett S.
- CHRIS A.


4.
Describe the three different types of life cycles.
----
Animals- gametes are the only haploid cells- meiosis occurs during the production of gametes- the diploid zygote divides by mitosis
Plants- The diploid stage is called the sporophyte- meiosis in the sporophyte produces haploid cells called spores- spore divides mitotically to generate a multicellular haploid stage called the gametophyte
Fungi- After gametes fuse and form a diploid zygote, meiosis occurs without a diploid offspring developing. Meiosis produces not gametes but haploid cells that then divide by mitosis and give rise to a haploid multicellular adult organism.



-Ryan H.



5.
What exactly is meant by alternation of generations?
----Alteration of generations is the switching between haploid and diploid cells generation to generation.
alteration_of_generation.jpg

The image above shows the switching between haploid and diploid cells. Mitosis and Meiosis are also involved, and the image does a good job of portraying their important role. 


This video explains the alteration of generation by using moss reproduction. It describes the process of alteration by showing the switch between haploid and diploid cells within the plant. This video also includes meiosis and mitosis, and the role each process serves for moss reproduction.


6.
Upload a diagram or video that describes the steps of meiosis.

external image meiosis.gif
^ This diagram above shows how Meiosis is conducted as well as the video --> This guy is sooo funny hahahaha!





7. What are the two broad goals of meiosis?
1. Produce haploid daughter cells.
2. Generate Variation
external image meiosis1.gif

8. Summarize the comparison of mitosis and meiosis. Upload pictures that highlight the differences.

external image 2_mitosis_meiosis.jpg
^^ This picture shows the differences between meiosis and mitosis. - Fernanda R.

9.Describe in detail the three sources of genetic variation in meiosis.

    1. Independently assorted chromosomes- In metaphase one, there are several ways homologous chromosome pairs are arranged. When they are lined up, there is a chance that one daughter cell will get the paternal chromosome and an equal chance that it will get the maternal one. This 50/50 split can occur with any homologous chromosome pair. The greater the number of chromosomes in a set (n), the more chances a daughter cell has to divide its paternal and maternal chromosomes equally among itself, and the more diverse the gamete population will become.
Random assortment creates different gametes
Random assortment creates different gametes

    1. Genetic Recombination (Crossover)- In Prophase I, a specific event occurs when the chromatids of both homologous chromosome pairs (one from each parent) bring their �arms� together and attach by a protein structure called the synaptonemal complex. The sister chromatid pairs come very close together. Now, one set of non-sister chromatid pairs (one from each original pair) is close enough to cross gene strands with its foreign neighbor. When the strands of chromosome cross, they break off and attach to their adjacent chromosomes, effectively changing the codons in that gene and those of the daughter cell that will receive that chromatid. These recombinant chromosomes are like hybrids, built up of pieces from both parents (like some sort of Frankenstein chromosome). This also increases the variety of potential gametes produced in meiosis.







3. Random Fertilization- Due to all the variations between individual gametes, there are many potential combinations that can occur to form a zygote. Take the human zygote. Each sperm or egg is one or 8 million potential gametes! Now match that with the probability of one sperm out of a few million wriggling its way through to the uterus, reaching the egg intact, and penetrating it successfully! There are so many outcomes; it is no wonder such broad genetic differences occur within humans. It�s impossible not to be the product of a random pairing, at least without artificial means of fertilization. More choices=greater genetic diversity=more likely to develop different traits than siblings/other members of species=favorable traits win out=Darwinism.