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Chapter 16 Blog: Simple Patterns of Inheritance (John T aka Yianni)

Page history last edited by John Tamanas 13 years, 5 months ago

On this page you are required to add two items (link to a website, video, animation, student-created slide show, student-created PowerPoint presentation) and one journal article pertaining to a topic in this chapter.  A one-paragraph summary must accompany each item describing the main idea and how it applies to the lecture topic.  Please see the PBWorks help guide for assistance embedding video and other items directly in the page.  I will also produce a how-to video on using tables to wrap text around items and other useful tips.  Please see the syllabus for organization and grading details.


A.  Daily Blog aka Chapter Summarization


     About 150 years an Austrian-Augustinian Monk/Scientist by the name of Gregor Mendel was a pretty big deal. He practically discovered genetics. Mendel's experimental system was off the chain. He used pea plants that allowed for rapid reproduction of a macrosized organism with obvious traits. In addition, he used traits that assorted independently from each other. (This means that the the segregation of one gene does not affect the segregation of another.) For his experiments Mendel focused on a single characteristic being inherited. This is called a monohybrid cross. After a bunch (and I mean a bunch) of hybridizations, Mendel concluded that genes are made up of alleles. Alleles are basically two different forms of a gene, dominant and recessive, and genes are made up of two alleles in diploid cells. There is one allele per set of chromosomes. This means that gametes only have one allele in their DNA because the alleles separate during meiosis. This is called Mendel's principle of segregation. Mendel then went on to use dihybrid crosses. The Principle of Independent assortment was then created by analyzing the offspring. Mendel concluded that alleles of different genes are inherited independently from one another. These experiments and discoveries then lead to the Chromosome Theory of Inheritance. This theory has 5 main principles: genes are found on chromosomes, chromosomes are replicated and passed from parent to offspring, the nucleus of a diploid cell contains two sets of chromosomes, one member of each chromosome pair segregates during meiosis, and gametes are haploid cells that combine to form a diploid cell during fertilization. The Chromosome Theory of Inheritance helps physically explain Mendel's theory of independent assortment. It shows us that chromosomes randomly align on the metaphase plate during meiosis. This theory of inheritance allows us to study pedigrees to see the inheritance of genes in families.


     In a pedigree members of the family are represented as squares or circles for males and females, respectively. Shapes that are fully shaded represent people with the phenotype being traced, people shaded in means that they do not exhibit the phenotype but are heterozygous for the gene. Using simple Mendelian genetics and some knowledge about the genes, you can figure out what traits you have, and possibly your genotype. If you have a pedigree, and need to figure out some details about a certain gene from it, you can! For instance, if there isn't a carrier, but there are people affected by the gene, then that means the gene is expressed by the dominant allele. 


     Speaking of sex chromosomes, different animals have different methods of determining sex. Mammals have the X-Y system. Meh, that's boring. Certain insects have the X-O system. This means that sex is determined by the amount sex chromosomes, not the kind. Birds have the Z-W system. This system is pretty much the opposite of the X-Y system. Lastly, there is the haplodiploid system. This system determines sex by the amount of chromosomes in the animals' body. This is found in bees. Sex chromosomes were also studied in flies. This study led to the discovery of X-linked chromosome heredity. This means that if a gene is found exclusively on the X chromosome, a recessive allele can be expressed, even if there is only one copy. This further helped with the Chromosome theory gain "credibility".


     Unfortunately, Mendel kinda lied to us. If we were to interpret his results we would result in an oversimplification of genetics. There are several other factors. Genes could be X-linked (discussed previously), have incomplete dominance(Protein is made from the dominant allele, but not enough to have its phenotype), have codominance (Both dominant and recessive proteins are made and therefore expressed), and lastly sex-influenced inheritance is a factor (Sex hormones affect the molecular expression of genes). Another thing that makes the phenotype different is the environment. Certain environmental conditions cause certain genes to be expressed more. This could result in a taller plant, for example. Lastly, genetics is a science with a heavy math background. Geneticists use what they know from their studies to determine the probablity of certain genotypes being passed down from parent to offspring. Geneticists use the rules of addition and multiplication to aid in their statistical analyses. We're amazing statisticians, though, so I don't need to go into that.




B.  Useful Materials



This is a really basic introduction to genes. It gives us examples like punnet squares, asexual and sexual reproductions, and chromosomes. Oh and it happens to be a rap. http://www.youtube.com/watch?v=8hKBHUaPo3I this rap goes into a little more detail, and it's A LOT better. 



This article talks about the lack of research in Mendelian diseases. I'm guessing rectal carcinoma (butt cancer), is one of these. These scientists took rectal carcinoma cells replicated them until they had 64 clones. They discovered 9 over-expressed genes in the cells. I think this could be a useful way to do research on Mendelian diseases. 


This video is pretty much a review from last chapter and this chapter and evolution. Yay youtube!

Comments (1)

Derek Weber said

at 2:47 am on Apr 2, 2011

The second song was tight son.

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