Wednesday, April 8th: Introduction to Genetic Disorders

Yesterday, you read an article about mutations.  Let's start today by going over answers to those four review questions:

Question 1: Are mutations typically beneficial to the organism?
No.  It is rare that mutations are helpful and can help an organism survive better in its environment. Some mutations can be harmful and cause diseases like cancer.  Many mutations are neutral and have no noticeable effect or have an effect that isn't really good or bad. 

Question 2: What can cause DNA to mutate? 
Some mutations are caused when a cell makes a mistake during DNA replication.  Some mutations happen spontaneously, which means it's a random mutation without a clear cause.  Certain situations in an organism's environment could cause mutations.  Environmental factors that cause mutations are called mutagens.  Chemicals from smoking are one example of a mutagen.

Question 3: What is a frameshift mutation?
A frameshift mutations is when just one or two nitrogen bases are added or deleted.  This causes the codon sequence to change dramatically. 

For example, let's say this is the normal DNA sequence:
     A A C    G T A     C C A     C A G   

If just one extra nitrogen base gets inserted at the beginning of the sequence, the whole sequence changes:
     A G A    C G T    A C C     A C A   G

Remember, the mRNA copies this code and gets read 3 nitrogen bases at a time and each set of 3 bases (codon) codes for a specific amino acid.  If the directions for a protein get mixed up, a totally different protein will be created.

Question 4: Describe two types of chromosomal mutations.
Remember that chromosomes are the x-shaped DNA holders inside of a cell's nucleus.  A chromosomal mutation is a big mutation that affects a whole chromosome.  This will likely affect many different genes. 

The types of chromosomal mutations your read about were:
     Deletion- A section of a chromosome is missing.
     Duplication- When a section of DNA is repeated.
     Inversion- When a section of DNA gets flipped upside down.
     Insertion- When an extra section of DNA is added to a chromosome.
    Translocation- When DNA from two chromosomes trade places.

In science fiction, DNA mutations are often the cause of super heroes being created.
Teenage Mutant Ninja Turtles were created when baby turtles got exposed to
radioactive ooze that caused their DNA to mutate.  

Today's Assignment:
Read THIS ARTICLE to get an overview of genetic disorders and diseases caused by mutations.  There is some pretty big vocabulary in this article.  Don't worry about understanding every detail.  Your goal is to get the big picture.

When you finish reading, there are four questions for you to answer.  Please email or DM your answers to Ms. Dolan.  (adolan@hccs481.org   or   ms.dolans_science).