--Cell division: Mitosis
--Mitosis vs. Meiosis
--Cancer
--Genetic Inheritance: Simple and Complex
--Sex-Linked Inheritance
--Genomics and DNA Technology
**Cell division: Mitosis**
A cell cycle has two parts: interphase and mitosis. Interphase consists of G1 (cell doubles its organelles), S (DNA replication occurs), and G2 (the cell synthesizes the proteins needed in preparation for cell division). Mitosis consists of prophase, metaphase, anaphase, telophase. Then, nuclear division and cytokinesis occur.
Mitosis is the usual method of cell division, characterized typically by the resolving of the chromatin of the nucleus into a threadlike form, which condenses into chromosomes, each of which separates longitudinally into two parts, one part of each chromosome being retained in each of two new cells resulting from the original cell. (Mitosis).
*Apoptosis - programmed cell death - gets rid of cells dividing that should not be dividing.
According to Mader on pg. 382-383 in early prophase, the centrosomes duplicates and the chromatin combines to form chromosomes. In prophase the nucleolus disappears and the now duplicated chromosomes can be seen. The centrosomes begin to move away from each other and the spindle begins to form. In early metaphase, attached to spindle fibers are each chromatid. Metaphase is where the centromere of the duplicated chromosomes make a line in the center of the cell, around the spindle. During anaphase, the chromatids break apart and become daughter chromosomes moving in the direction of the spindle poles. Telophase is where is all comes together. The daughter cells are forming as nuclear envelopes and nucleoli reappear and chromosomes once again become unnoticed as chromatin.
**Mitosis vs. Meiosis**
Mitosis/Meiosis I/Meiosis II
Prophase/Prophase I/Prophase II
No pairing/Pairing of homologous chromosomes/No pairing
Metaphase/Metaphase I/Metaphase II
Duplicated chromosomes at equator/Homologous duplicated chromosomes at equator/Haploid number of duplicated chromosomes at equator
Anaphase/Anaphase I/Anaphase II
Sister chromatids separate, becoming daughter chromosomes that move to the poles/Homologous chromosomes separate/Sister chromatids separate, becoming daughter chromosomes that move to the poles
Telophase/TelophaseI/TelophaseII
Two daughter cells, identical to the parent cell/Two haploid daughter cells/Four haploid daughter cells
Meiosis produces half the number of daughter cells than that of mitosis. Since the homologous chromosome pairs separate during anaphase I, the daughter cells are said to be haploid.
**Cancer**
Cancer Cells Lack Differentiation: They don't help the body function and they don't look like the other cells.
Cancer Cells Have Abnormal Nuclei: Enlarged and may have abnormal number of chromosomes. The chromosomes may have parts that are duplicated and parts that have been deleted. Extra copies is commonly found. They do not perform apoptosis.
Cancer Cells Have Unlimited Replicative Potential: Cells normally divide 60-70 times before they die but cancer cells don't die and can continue to divide. The breaking apart of the binding of chromosomes, telomeres causes a cell to undergo apopstosis. Telomerase rebuilds the telomeres in cancer cells, keeping them alive.
Cancer Cells Form Tumors: Cancer cells pile on top of one another and grow in layers creating a tumor. Benign tumors won't invade adjacent tissue. Cancer in siu, however doesn't necessarily have a capsule around it.
Cancer Cells Have No Need for Growth Factors: Do not respond to inhibitory growth factors.
Cancer Cells Gradually Become Abnormal: (Mader, 405) Carcinogenesis:
1. Initiation: a single cell mutates, causing it to start dividing constantly.
2. Promotion: a tumor develops and those cells continuously divide as they take on mutations.
3. Progression: one cell mutates, giving it an advantage over the rest. Usually this repeats several times to where there is a cell that is able to invade surrounding tissues.
Cancer Cells Undergo Angiogenesis and Metastasis: Angiogenesis- formulation of new blood vessels; provides the tumor cells with oxygen and nutrients needed to survive. Metastasis- new tumors form far away from the primary tumor. (1 in 10,000 cancer cells do this successfully).
Leading cancer killer for males in 1993? Lung and bronchus- 92,493 deaths. Females in 1993? Lung and bronchus- 56,234 deaths.
Standard therapies: surgery, radiation (focuses on one part of the body), chemotherapy (catch cancer cells, treats the entire body), immunotherapy (use of Melacine, genetically engineered cells, monoclonal antibodies) , p53 gene therapy (19 hours to trigger apoptosis), and others.
**Genetic Inheritance: **
One trait Crosses: Create a Punnett Square using all the possibilities. Two monohybrids create a 3:1 ratio of expected offspring. A monohybrid and a recessive are expected to create a 1:1 ratio of offspring.
Two trait Crosses: If two dihybrids cross (MmNn x MmNn) there is a 9:3:3:1 ratio expected of the offspring. If there is a dihybrid and recessive, they are expected to have offspring with a ratio of 1:1:1:1.
Dominant traits vs. Recessive traits
Multiple alleles provide that every thing has two out of three possible alleles. "IA" and "IB," which are both expressed and serve as codominance. The third, "i" is not expressed.
The X chromosomes carry genes that may be unrelated to the gender of the individual. For instance: XBXb x XBY produces all daughters being normal but with a 50% chance of being a carrier, while the sons have a 50% chance of being color-blind. Now, XBXB x XbY makes it so that all the children will be normal, though all the duaghters will be carriers of the color-blind factor.
**Genomics and DNA technology**
www2.carthage.edu
Thanks to the Human Genome Project, we now know the 3 billion bases of our own genome. (Sperm DNA and white cells from the blood of female donors: European, African American, and Asian)
"...genome size is not proportionate to the number of genes and does not correlate to complexity of the organism." (Mader, 454)
Laboratories can analyze up to 2 million bases in a day.
25,000 genes function in our cells.
There are gene deserts, known as the 82 regions, 3% of the genome, where DNA doesn't have any identifiable genes.
Chromosome 22 in chimps compares to humans.
We are 99% alike with chimpanzees in base sequence.
All vertebrates have very similar genomes.
Humans are 88% alike to a mouse.
Ex vivo is gene therapy performed on the outside of the body and in vivo is performed inside the body.
Ex vivo: treating children who have severe combined immunodeficiency (SCID)
In vivo: cystic fibrosis patients
It's believed that with genetic modification people will be able to live longer, healthier lives with new medicines available, and that you may even be able to pick your child.
*DNA technology may even cure cancer one day.
Recombinant DNA (DNA from two or more sources) makes it possible for genes to be cloned which may be used for a new and different purpose. For example, transgenic bacteria is grown to produce medicines. Transgenic animals and plants have increased the world's food supply which has, in turn, made it possible for us to thrive and continue on with our increasing population. Due to a growth gene insertion, certain salmon weigh more and reproduce a lot faster. Also, plants are being injected with pest inhibitors that keep bugs from eating them. This issue arises because some argue that by keeping the bugs away we are taking away their food supply, thus, they are reducing in numbers themselves. Sounds good, but the tables turn when one realizes that those bugs ate other bugs and now those bugs are thriving due to the loss of one.
*Works-Cited*
"mitosis." Dictionary.com Unabridged (v 1.1). Random House, Inc. 13 Jun. 2007.
Picture representing mitosis:
Picture representing mitosis vs. meiosis:
Picture representing cancer treatment:
Picture representing simple and complex genetic inheritance:
Picture representing sex-linked genetic inheritance:
Picture representing genomics:
www2.carthage.edu
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