1.5 Genetic Mutations and Inheritance

Genetic Changes

What do you think of when you hear the word mutation? Perhaps you've seen how Hollywood movies use mutations to create superheroes or evil villains. In biology, a mutation is really just a change within a gene. You will learn in this chapter that mutations have different causes and effects on living things, and not all mutations are bad!

Jurassic Park-Mr. DNA

Jurassic Park is a 1993 American sci-fi hollywood movie. It was followed by 3 sequels and a fifth is scheduled for release in 2018. The plot centers around industrialist John Hammond and his bioengineering company, InGen,who have created a theme park called Jurassic Park on Isla Nublar, a Costa Rican island, populated with cloned dinosaurs. Watch the segment from the film where at the park's visitor center, the scientists learn that the cloning was accomplished by extracting dinosaur DNA from mosquitoes that had been preserved in amber. DNA from frogs was used to fill in gaps in the dinosaur genomes. To prevent breeding, all the dinosaurs were made female.

Hollywood Style Quiz

Instructions

Before you begin this lesson, try the “DNA…Hollywood style!” quiz to see if you can separate real science from Hollywood drama! The X-men film introduces a Brotherhood of Mutants who intend to mutate world leaders at a United Nations summit with a machine built to bring about acceptance of mutantkind. There have been 7 X-men sequels since the fisrt X-men film release in 2000.

Recent research into mutations that cause cancer has shown that antibodies might be able to recognize cancerous cells. Maybe in the future, antibodies could combat mutations after all!

Types of Mutations-Gene Mutation

In biology, we define mutation as a permanent change in an organism's DNA. Mutations are sometimes inherited by offspring. In this lesson, you will explore mutation that occurs at the gene level and at the chromosome level of DNA organization.

A gene mutation is a change in the normal base sequence of a gene. Gene mutations involve one or more base changes in a single gene, and take place when chromosomes duplicate during interphase. There are three types of gene mutations. A nucleotide base might be:

• deleted

• added

• substituted

In each case, the mutation changes an organism's genetic code, and these changes can be passed to offspring.

Types of Mutation-Chromosomal Mutations

Chromosomal mutations are mutations that occur during meiosis. They involve a large amount of DNA than a gene mutation. This means that a chromosome mutation can affect many different genes.

Mutations-Guided Practice Vocabulary

Mutations Causes and Effects

Mutations occur naturally, but they are also caused by UV radiation (for example sunlight) or chemicals (for example cigarettes, pesticides and some food preservatives).

Mutations can also be genetic (inherited from parents and passed on to children). For example, Down syndrome (also called Trisomy-21) is caused by an extra copy of the 21st chromosome.

Whatever their cause, mutations don't always have the same effects. A mutation can be

• positive: the mutation is beneficial to an organism, helping it to survive and reproduce. Positive mutations can also turn on genes beneficial to the organism or turn off genes that are harmful to the organism.  For example - you can mutate a piece of bacterial DNA that was "turned off" to turn it on- this can make it less susceptible or more susceptible to antibiotics. It would be beneficial to the bacteria, but detrimental to us if we are trying to get rid of it.

• negative: the mutation reduces the organism's chance of surviving and reproducing. Many pesticides and herbicides target the species by blocking a protein from being made by altering (mutating) the DNA. Some antibiotics work by blocking DNA synthesis or protein synthesis in the bacteria, causing bacteria to die. If the bacteria mutates to no longer need the specific protein, then the antibiotic becomes useless.

• neutral: the mutation doesn't affect the organism's ability to survive

Click here to learn more about the pros and cons of mutations.

Detecting and Treating Genetic Disorders

Consider this scenario: Lisa has a brother and a sister. Their mother died of cancer, and Lisa has had breast cancer. She has undergone radical surgery and chemotherapy. She is now cancer-free, but lives in fear that her cancer will return.

Her brother and sister want to know whether they also have cancer. Do you think they should be tested for the “cancer gene”? What will they do with the information this testing gives them?

As you can imagine, there are many ethical issues surrounding genetic disorders. For example, should medical insurance companies be allowed to charge higher life insurance rates for people who have the “cancer gene”?

One way to identify a genetic disorder is karyotyping (chromosome analysis). Karyotype is a test to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells. Extra or missing chromosomes, or abnormal positions of chromosome pieces, can cause problems with a person's growth, development, and body functions. Chromosome analysis can be done on blood, tissue, or cells from amniotic fluid (the fluid that surrounds the baby in the womb). 

If an individual has a gene mutation, gene therapy may be a possible treatment. This is more a future option than a current one, although some tests have been done to see if gene therapy works.

Where Does Cancer Fit In?

Not all mutations will be passed on to the next generation. A mutation in a normal body cell (any kind except specialized sex cells) can result in cancer. Cancer is a term used to describe uncontrolled cell division.

The following table compares normal cells to cancer cells:

There are many different types of cancers, and their severity depends on where they are located. For example, a young person diagnosed with thyroid cancer can undergo surgery, radiation and hormone treatments. This type of cancer has a high survival rate. Other cancers, such as brain cancer, have much lower rates of survival.

Meet Sam Berns

Sampson Gordon "Sam" Berns (October 23, 1996 – January 10, 2014) was an American teen who had progeria and helped raise awareness about the disease. He was the subject of the HBO documentary Life According to Sam, which was first screened in January 2013. He died one year later, after appearing in a TEDx Talks video titled "My philosophy for a happy life."

Progeria affects approximately one in every 4 million to 8 million infants; there are only about 200 children living with it worldwide. The genetic mutation tied to it causes those with the disease to produce the protein progerin, which blocks normal cell function. As they age rapidly, these children suffer from a loss of body fat and hair and an inability to gain weight. They are prone to developing osteoporosis, a disease where bones become weak and are more likely to break.

Mutations-Guided Practice Quiz

Instructions

Complete this quiz by selecting the correct answer.