Biology Test Review for Monday

Here it is...
Biology Review Test 5
Angus/Erickson
1. What is Cell Division?
1. Cell division is the process by which cells reproduce.
2. What is chromatin?
1. Chromatin is a mass of long, thin fibers composed of DNA and protein molecules.
2. It is basically coils of DNA wrapped around bead-like proteins
3. What are homologous chromosomes? What are sister chromatids?
1. Homologous chromosomes are chromosomes that are alike in length, centromere position, and gene loci (the same in size and genes that are coded for). They are equivalent but not identical
2. Sister chromatids are the two identical parts of a duplicated chromosome (each “line” of the x)
4. What is the cell cycle? What are the phases? What happens in them?
1. The cell cycle is an ordered sequence of events in a cell from the time that it is formed until it divides.
2. The parts are G1, S, G2, and M
i. In G1, normal cell function and growth occurs
ii. In S, the cell copies its genetic material (DNA in the form of chromosomes). The cell moves from unduplicated to duplicated, but not haploid to diploid. The cell continues to grow.
iii. In G2, the cell completes its growth and preparation for cell division
iv. In M, the cell divides. In mitosis, the nucleus and its contents are evenly distributed to form two daughter nuclei, and the cytoplasm is divided in cytokinesis
1. Thus, two genetically identical daughter cells are produced
3. However, some cells enter G0, a state in which a cell will not replicate (for example, some nerve cells)
5. What is the difference between haploid and diploid?
1. A cell is haploid when it has one of each type of chromosome. The haploid number is the number of different types of chromosomes
2. A cell is diploid when it has two of each type of chromosome (one from the mother and one from the father) The diploid number is always twice the haploid number in normal cells.
6. What are the two main types of cells in sexually reproducing organisms?
1. The two types of cells are somatic cells and gametes
i. Somatic cells are all cells not directly involved in reproduction
ii. Gamates are haploid cells used for reproduction
7. What is mitosis? What are the phases? What happens in each phase?
1. Mitosis is a cellular process in which the nucleus and its duplicated contents are evenly distributed to form two daughter nuclei
2. The phases are prophase, prometaphase, metaphase, anaphase, telophase
i. In prophase, the nucleus begins to break down, the chromatin begin to compress, the centrosomes begin to move to either end, and the spindle fibers begin to form
ii. In prometaphase, the nuclear envelope is almost completely destroyed. The spindle fibers begin to attach to the kinetochores, and the chromosomes begin to line up in the middle of the cell.
iii. In metaphase, the chromosomes are completely lined up, and the spindle fibers are fully formed and attached
iv. In anaphase, the spindle fibers simultaneously push the centrosomes apart and pull the chromosomes towards each centrosome, causing the chromosomes to split into daughter chromosomes
v. In telophase, the daughter nuclei begin to form around the chromosomes as the cell elongates and forms a cleavage furrow
vi. Then in cytokinesis the cell splits!
8. What is the difference between sexual and asexual reproduction?
1. Asexual reproduction produces an exact copy of the parent organism, allowing for very little variation (only by mutation)
2. Sexual reproduction produces genetically varied offspring by combing DNA from both parents
9. What is meiosis? What is the purpose of meiosis? What type of cell does it produce?
1. Meiosis is a process of cell division that produces haploid gametes in diploid organisms.
2. Meiosis has two purposes
i. To produce haploid gametes
ii. To increase genetic variation
3. Thus, it produces haploid gametes
10. How many divisions are there in meiosis?
1. Meiosis has two division, one to go from diploid to haploid and one to go from duplicated to unduplicated
11. What are the phases of meiosis? Be familiar with what occurs in each phase. Be able to draw or recognize each phase?
1. Prophase I- The chromatin compresses and homologues come together to form tetrads in a process called synapsis. This is where crossing over occurs. The centrosomes go to each side and the spindle fibers begin to form
2. Metaphase I- The chromosome tetrads pair up at the middle of the cell. The spindle fibers attach to centromeres. The homologues are still held together at the chiasmata but will go in different directions for the rest of meiosis
3. Anaphase I- The spindle fibers retract the chromosomes but only the tetrads split, not the chromosomes
4. Telophase I and Cytokinesis- The cell splits, forming two duplicated haploid cells
5. Prophase II- The centrosomes move to either side and the spindle fibers begin to form
6. Metaphase II- The chromosomes line up and the spindle fibers attach
7. Anaphase II- The chromosomes split and retract to either side, thus becoming unduplicated
8. Telophase II and Cytokinesis- The cell forms a cleavage furrow as the nucleus forms around the now unduplicated chromosomes. The cell splits and we now have (in sum) four haploid unduplicated gametes!
12. What is the key phase in meiosis and why?
1. The key phase in meiosis is Prophase I. This is where synapsis, one of the main sources of variation occurs. The swapping of genetic material between homologues allows for almost infinite variation. While the random assortment of homologues in Metaphase I is important as well, it only results in 2n variations.
13. What is the difference between spermatogenesis and oogenesis?
1. Spermatogenesis produces four fully functional gametes (the sperm) but because oogenesis has uneven division of the cytoplasm, it produces one functional egg and three polar bodies which only pass into The Force.
14. How does meiosis differ from mitosis? Give several differences?
1. Metaphase v. Metaphase I: In metaphase, the chromosomes align at the center, while in metaphase I, the tetrads align.
2. Mitosis goes from duplicated to unduplicated while Meiosis I goes from diploid to haploid
3. While there is only one duplication (during interphase), there are two divisions in Meiosis and one in Mitosis
15. What are the two sources of genetic variation in meiosis?
1. The crossing over between homologues
i. The pairing of homologues in Prophase I resulting in a tetrad allows for a nearly infinite combination of genetic material through genetic recombination
2. The random assortment of homologues
i. During Metaphase I the chromosomes pair up (because they are in tetrads), resulting in 2n possible combinations of chromosomes
16. What is nondisjunction?
1. Nondisjuction occurs when the chromosomes of a tetrad fail to separate from each other during Meiosis I or Meiosis II.
i. If it occurs in Meiosis I, the cells resulting have n+1, n+1, n-1, and n-1 chromosomes
ii. If it occurs in Meiosis II, the cells resulting have n+1, n-1, n, and n chromosomes
17. What is a karyotype? How is it obtained
1. A karyotype is a photographic inventory of an individual’s chromosomes
2. It is taken when scientists stimulate cells (typically lymphocytes) into forced mitosis. After several days, they are again arrested at metaphase, when the chromosomes are most highly condensed
18. What is the relationship between cancer and the cell cycle?
1. Cancer occurs when a cell doesn’t heed the normal signals that regulate the cell cycle (the cell cycle checkpoints). Cancer cells can divide infinitely as long as they have a supply of nutrients.
19. What are the differences between animal and plant cell division?
1. In an animal cell, the cell forms a cleavage furrow during anaphase as microfilaments contract around the cell membrane
2. However, since a plant cell cannot “contract” its cell wall, it must form a plate in between each daughter nucleus. The plate eventually joins with the outer cell wall, forming new cells

Vocab Terms
1. Cell Plate- A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.
2. Centriole- A structure in an animal composed of cylinders of microtubules arranged in a 9 and 0 pattern. An animal usually has a centrosome with a pair of centrioles involved in cell division.
3. Centromere- The region of a duplicated chromosome where two sister chromatids are joined and where spindle fibers attach during mitosis and meiosis. The centromere divides during anaphase and mitosis and anaphase II during meiosis.
4. Cleavage Furrow- A shallow groove in the cell surface near the middle of the cell, the first sign of cytokinesis in an animal cell
5. Cytokinesis- The division of the cytoplasm to form two separate daughter cells. Cytokinesis usually occurs during telophase of mitosis. Mitosis and cytokinesis make up the M phase of the cell cycle
6. Nucleosome- The bead-like unit of DNA packaging in a eukaryotic cell, consists of DNA wound around a protein core madae up of eight histone molecules
7. Replicated Chromosomes- A chromosome made up of two identical sister chromatids. (The x-looking thingy)
8. Unreplicated Chromsomes- A single chromosome not attached to anything. Looks like a line.
9. Sister Chromatids- The two identical unreplicated chromosomes that attach at a centromere to form a replicated chromosome
10. Kinetochore- The protein that reinforces the centromere in a replicated chromosome
11. Crossing Over- The exchange of segments between chromatids of homologous chromosomes during synapsis in prophase I of meiosis
12. Egg (ovum)- An unfertilized female gamete
13. Sperm- An unfertilized male gamete
14. Oocyte- A cell which a female produces at the early stages of her life. These undergo meiosis to form 3 polar bodies and an egg
15. Fertilization- The union of a sperm cell with the nucleus of an egg cell, resulting in a zygote
16. Zygote- A fertilized diploid cell resulting from the union of a sperm cell nucleus and an egg cell nucleus
17. Synapsis- A process by which two chromatids in a tetrad switch sequences of genetic material
18. Tetrad- A paired set of replicated homologous chromosomes. Tetrads form during Prophase I of meiosis
19. Chiasma(ta)- The microscopically point where crossing-over has occurred between chromatids of homologous chromosomes during prophase I of meiosis
20. Autosome- A chromosome not directly involved in determining the sex of an organism (in mammals, not x or y)
21. Sex chromosomes- The chromosomes that determine the sex of an organism (x and y in mammals)
22. Monosomy and Trisomy- The lack or addition (respectively) of a chromosome in an organism (often because of non-disjunction)
23. Down Syndrome- Trisomy 21. Results in heart and respiratory defects and varying degrees of mental retardation
24. Turner’s Syndrome- Occurs when a non-disjunction causes an organism to lack one of two X chromosomes (XO). Typically has very little result. Occurs in approximately 1 in 5000 people
25. Klinefelter’s Syndrome- XXY resulting from non-disjunction. Occurs in 1 in 2000, causes inhibited sexual development resulting in sterility.

just a quick correction. On number 24, Turner syndrome is the lack of one X not the absence of both.

Biology Test: Ch. 8

1) Cell division is the reproduction of a cell. In single celled organisms, it’s the reproduction of an entire organism, but in multicellular organisms, it allows them to reproduce asexually. Also, among sexually reproducing organisms, it is the basis of sperm and egg formation.

2) Chromatin is the combination of DNA and histone protein molecules. When a cell prepares to divide, the chromatin coils up forming distinct chromosomes. I don’t know what the second part of this question is.

3) Homologous chromosomes are chromosomes alike in size and genetic material, but not identical because one is from the mom and one is from the dad. Sister chromatids are identical, replicated chromosomes with identical copies of DNA.

4) The cell cycle is the ordered sequence of events from the time a cell is formed to the time it divides into two new cells. It can be divided into three subphases: G1 phase, S phase, and G2 phase. In G1 phase, the cell grows. In S phase, the cell copies its chromosomes, and in G2 phase, the cell grows more to prepare for division. All three of these happen during Interphase of the cell cycle. Apart from Interphase, the other main phase is the Mitotic phase, or M phase. During M phase, the cell undergoes Mitosis and Cytokenesis, in which the cell is divided into 2 identical daughter cells.

5) A diploid is a homologous pair of chromosomes, (2n), (one from mom and one from dad) while a haploid is a single chromosome, or the number of different types of chromosomes (n).

6) The typical cell in sexually reproducing organisms called a somatic cell; a cell not directly involved in reproduction. The other type of cell in sexually reproducing organisms is a gamete: a haploid cell that combines with a haploid cell form the other parent (egg and sperm) to form a diploid zygote.

7) Mitosis is the part of the M phase when the nucleus and its contents divide and are evenly distributed among the 2 daughter nuclei. Mitosis is represented by 5 stages: prophase, prometaphase, metaphase, anaphase, and telophase. Cytokinesis isn’t actually a part of mitosis, but it is a part of the M phase. In prophase, the chromatin condenses to form visible, replicated chromosomes. Also, the nuclear envelope begins to dissolve and the centrosomes begin to migrate towards opposite poles. In prometaphase, the spindle fibers emerge from the centrosomes and move towards the middle of the cell. The nuclear envelope begins to break and dissolve and the chromosomes start to line up in the center of the cell. In metaphase, the spindles are fully formed, with one end at the centrosome and the other in the middle attached to the kinetochore of the chromosomes or to the spindle fibers from the opposite side. The chromosomes line up along the metaphase plate in the center of the cell. In anaphase, spindle fibers attached to the kinetochores pull back towards the centrosome while at the places where spindle fibers connected to each other, those push away thus elongating the cell. Lastly, in telophase, the cell continues elongating and daughter chromosomes reach the poles and uncoil forming daughter nuclei and the nucleolus reforms. Then the nuclear envelope begins to form and that concludes mitosis with an equal division of the nucleus into two genetically identical daughter nuclei.

In asexual reproduction, genetically identical offspring are formed from a single parent. In sexual reproduction, offspring are not identical to either parent, since there are two, but generally resemble their parents.

9) Meiosis is a type of cell division (nuclear division) that produces haploid gametes in diploid organisms. Its purpose is to produce lots of variation in haploid gametes.

10) In meiosis there are two meiotic divisions: one to go from diploid to haploid, and another to go from replicated to unreplicated.

11) Meiosis consists of 2 consecutive cell divisions; meiosis I and meiosis II. Meiosis I consists of prophase I, metaphase I, anaphase I, and telophase I and cytokinesis. Meiosis II has all the same steps, but with II’s after them. I’m not going into detail on these because they’re all in the book and if you don’t more or less know them by now, then you’re screwed anyways.

12) The most important step of meiosis is prophase I in the crossing over between homologues. When 2 homologous chromosomes undergo synapsis at a chiasmata, this results in almost unlimited variation whereas metaphase I only allows for 2n variation.

13) I can’t find this one in the book but Jon has it on his review.

14) There are 2 divisions in meiosis while there is only one in mitosis. In meiosis, the end product is 4 unreplicated gametes (haploid cells) while in mitosis the end product is 2 unreplicated diploid cells. In meiosis there can be more variation than in mitosis and generally in mitosis variation is bad. In metaphase I the chromosomes pair up instead of line up while in metaphase the chromosomes line up and get pulled apart into unreplicated chromosomes.

15) Crossing over between homologues and random assortment of homologues between cells. They occur during prophase I and metaphase I and allow for almost unlimited variation.

16) Nondisjunction is when, during anaphase, a chromosome fails to split resulting in one daughter cell with an extra copy of a chromosome and another daughter cell missing a chromosome.

17) A karyotype is a photographic inventory of an individual’s chromosomes. I don’t really understand past that.

18) A cancer cell arises from when a cell doesn’t have the proper checkpoints in the cell cycle or when it doesn’t recognize them. If then one cancer cell divides and functions on its own well enough to survive, then it can keep replicating whether it causes harm to the organism or not.

19) In cytokinesis in the plant cell, vesicles pinch off of the golgi body and form a cell plate in the middle of the cell between the two nucleus’s which eventually enlarges and expands to the edges to form two new cell walls for each of the new daughter cells.

For the important terms, most of them are in the back of the book and jon has all of them too. I didn’t really read jon’s review while making this so hopefully this can be a supplement to his if we both left out parts of the answer.

Isn't the key phase Metaphase I since he had us do *****METAPHASE I******

I don't really see what you're saying, but i can clarify my reasoning further-
In prophase I, there is a pairing up of chromosomes to create tetrads- This has two results:

There is now a nearly infinite amount of variation
Because the tetrads remain during metaphase I, the chromosomes are paired up instead of lined up, causing 2^n variants.

Since both of these result from the synapsis during Prophase I, it seemed like that would be the most important step. Can you explain what you're saying?

well in my notes I have stars around Metaphase I and I thought he also drew them on the board and said "this is very important"

and isn't this where it changes from a diplod to haploid?

"does that make sense?"

kk he definitely said that... who is this?

Hunter...lol

I should have figured that out from the name...

i dont remember any stars or anything...i thought the same thing as jon for this one

Its Metaphase I because it is the step that allows us to go from diploid to haploid and he made us star it in our notes.

oh ok

Vista doesn't go well into the forums, but this is how it works:
1: Primary (numbers)
a: Secondary (letters)
i: thirdary (roman numerals)

This site is great for understanding the concept of diploid vs haploid, and it uses the same terminology that we use. I recommend glimpsing over it before the test tommorow- look at the mitosis section then meiosis.

http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells3.html
http://www.biology.arizona.edu/cell_bio/tutorials/meiosis/main.html

BIOLOGY TEST TOMMOROW!