Compendium review Unit one #2

Unit I Compendium Review

Topic two: Genetics
-Cell division-mitosis
-Role of DNA/genes in controlling cell metabolism
-Recombinant DNA technology (genetic engineering)
-Early fetal development
-Role of Genes/chromosomes in inheritance
-Cellular basis for cancer

Cell Division-mitosis
When cells divide the new cell is called a daughter cell and it is genetically identical to the original “parent cell.” They contain the same genes or DNA. Inside a cell there are 23 pairs of chromosomes. Each pair is made up of 2 separate chromosomes attached together by a centromere. During mitosis the chromosomes separate and link up with a sister chromatid and becomes duplicated. There are four phases of mitosis: prophase, metaphase, anaphase and telophase. The phases are all continues they do not stop between them they all flow together. In the prophase the cell prepares to divide. The duplicated centrosomes move to opposite ends of the nucleus. The nucleolus disappears. “Spindle fibers attach to the centromeres as the chromosomes continue to shorten and to thicken.” (Mader pg382) In metaphase the spindle takes over where the nucleolus use to be. The chromosomes align at the center of the spindle. In the anaphase the chromatids divide or separate with one going to each side of the spindle. During telophase two nucleuses reappear each receives their own chromosomes. After this phase cytokinesis takes place. This is when the cell divides into two new identical cells. Cells grow to replace damaged worn out cells or for growth.

Role of DNA/genes in controlling cell metabolism
The nucleus (where the DNA is) decides the order of amino acids in proteins. The proteins in a cell run the cells metabolism. Chromosomes are formed when the cell is dividing. Chromosomes are formed in the nucleus. When a new cell is being made DNA makes a copy of it’s self so that the new cell is identical to the old one. DNA is like the instruction book for the cell.


Recombinant DNA technology (genetic engineering)

With recombinant DNA technology scientists can take human recognition proteins insert them into a pig embryo; then when the cells multiply the pig grows up with all of its cells containing human recognition proteins. This would make the pig’s organs more compatible to humans for transplants. Genes can be cloned by putting one set of DNA into a new host cell. Then when the cell multiplies it will be genetically identical to the donor DNA. Plants can be genetically engineered to be resistant to bugs or herbicides. They can insert genes into animals fertilized eggs then put them back inside the animal to grow. This way they can alter the animal to be larger or stronger. They can inject alleles for a human disease into mice embryos so that they can study the mouse after it is born. Then they can test medications on the affected mice.

Early fetal development

Meiosis is the start of fetal development. When a fetus develops it receives 23 pairs of chromosomes. Half of each pair is from the mom and the other half is from the dad. After the egg is fertilized the cells continue to split and multiply. Eventually the cells will form a human being.

Role of Genes/chromosomes in inheritance
Humans inherit on one allele from each parent, for each characteristic. Alleles are in pairs. Alleles determine if you will have red hair like your dad or brown like your mom. Your mom and dad both give you either a recessive or a dominant allele for each trait. It takes one dominant allele to cause a trait or two recessive alleles. A person can be homozygous dominant for a trait this means that they will always pass on that dominant gene. Or a person could be homozygous recessive meaning they always pass on a recessive gene for that trait. The other possibility is heterozygous meaning they could pass on a dominant or recessive gene. When a child is formed the mother’s egg carriers the recessive or dominant gene. It meets with the sperm that also contains a dominant or recessive gene. This is how the pair of genes or alleles is created. So to explain further if your parents both have a dominant gene for big feet then the chances of their child getting big feet is 100%. If one parent is dominant and one is recessive the child will also receive big feet. But if one parent is recessive and the other is heterozygous they child could end up with the recessive trait (small feet.) So every detail about our body is decided by the genes or chromosomes we receive from our parent


Cellular basis for cancer
Cancer cells are abnormal they do not resemble any other type of cell. They do not serve a function like other cells in the body. The nuclei in cancer cells are abnormal they are larger than normal ones. They can also have abnormal numbers of chromosomes. Cancer cells do not die they just keep reproducing. Normal cells die after dividing 60-70 times. Normal cells connect to their neighbors and stop dividing. Cancer cells just keep multiplying and pile on top of each other. Cancer invades other areas and tissues. A tumor that is benign doesn’t invade other tissues because it is encapsulated. Since it is surrounded by a capsule it is prevented from invading other areas. Cancer is caused by a cell that develops a mutation. Then it begins to reproduce it’s self rapidly. Cancers are a lot of times hereditary meaning you can inherit the cancer gene from your parents or relatives in your family tree. Chemical s can cause cancer as well. These chemicals are called carcinogens. Radiation from x-rays, ultraviolet light from tanning or sun light can cause cancer. There are five times more cases of skin cancer a year than lung cancer. Tobacco is a major cause of cancer because of all the added chemicals in it. The chemicals are known mutagens. This means that they are known to mutate cells and cause cancer. Pesticides and chemicals like asbestos, radon and benzidine also increase the risk of getting cancer. There are also viruses that can cause cancer; like hepatitis B, C, and HPV.



Work Cited:
Madder, Sylvia S. “Human Biology” 10th ed. New York: McGraw-Hill, 2007.
Picture of blastocyte: http://www.paternityangel.com/Preg_info_zone/WeekByWeek/Weekly01.htm
Picture of Mitosis: http://www.enchantedlearning.com/subjects/animals/cell/mitosis/label/
Picture of Cancer cells: http://www.cancer-info.com/canpic.htm
Picture of pig organs: http://www.newbedford.k12.ma.us/srhigh/oliveira/organsgeneralb.html

Picture or eyes:http://www.dushkin.com/connectext/psy/ch02/eyes.mhtml

Picture of DNA:http://members.lycos.nl/TheDNApage/dnapix/lbdna24p.gif