MUTATIONS

Hi guys, as you know I'll be your temporary Biology teacher for a while, until the school find and hire an English-speaking teacher. 
Eventhough I don’t  mastered the language, I have the ability to design exercises, assignments and tests in English and also to evaluate them. 
I'll use videos in English which I have sought and chosen among several in order that you can learn scientific terminology in both, Spanish and English lenguages, so you will be able to present the IB exams in the language of your choice

Mutations

Mutations are random changes in the base sequence of a gene.  Mutations can occur naturally, due to errors in gene transcription or during DNA replication.

Although most of these mutations are repaired, and when they don’t, often have negative effects on the organisms, mutations are in fact a source of genetic variation for the evolution, since the new alleles that are formed can represent eventualy an adaptive advantage for the specie.

High energy radiation and mutagenic  chemicals  increase the rate of mutation, and can cause changes in alleles that have been selected over millions of years, so that, these changes are detrimental in most cases. In addition, mutations in genes that control cell division can cause cancer, because the cell begins to divide uncontrollably until it forms a tumor.

Look at the videos I put down here, so you can understand how the different types of mutations occur and how they affect or change the information contained in the DNA.

HOMEWORK:

Analize the information given on page 46 of your Biology book and:

1. Resume and comment the 5 points about the effects caused by the nuclear accident at Chernobyl.  
2. Discuss whether the evidence from registered cases of people dying of cancer or leukemia, and malformations observed in children who were fetuses when the atomic bombs were detonated, is sufficient enough to confirm the hypothesis that the radiation is directly related with the presence of these diseases on people who were exposed to it. 
3. The next excercise was taken from the thick book, your task is:

• Analyze the following graph and answer:  "When would you expect the cases of thyroid cancer in young adults to start to drop, based on the data in the graph?

Sickle-Cell anemia
We will now review the case of a disease caused by a point mutation, a change of a single base in the sequence of a gene.

To understand this, we will review the concepts of gene and allele. As we see before, gene is a particular base sequence that codes for a specific characteristic. That gene will always be located on the same chromosome and at the same site within that chromosome (locus). 

From this it follows that on each chromosome there are several genes, therefore there are many more genes than chromosomes in any organism (see the data on page 47 of your study guide book) and there is a certain relationship between the complexity of the organism and the number of genes, this is true for the case of prokaryotes and animals, in plants this relationship is not, due to the presence of other survival strategies, that can be reflected in a remarkable increase in the number of genes, without it being related to its Complexity as an organism.

Moreover, organisms have more alleles than genes, since the same gene has more than one allele. The alleles are then versions of a gene, that means, they code for the same feature and are in the same locus, but they code for a different mode of the same characteristic, for example the black or brown color of the mice.

Now, please read the information given about the Sickle-Cell anemia and its relationship with Malaria which is in page 47 of  your student book. After that, look at the next two videos.

DNA sequencing  is a set of techniques used to know base sequence of genes whithin the DNA. It is used for many purposes, both for basic research and practical issues. 

Knowing the base sequence of genes, allows us for example, to establish how close a species is to another, or if a person has the gene of a disease that can inherit to their children, or to select a specific gene to inser it in another specie.

Now look at page 48 of your book, read it carefully an take note of the different databases that are available on the web and can be consulted at any time. Write down their names and the content they offer, because eventually we are going to use them.