Reading Check 4.2 Pg. 141

2. What is a gene mutation?

A gene mutation is a change in the specific order of the A, G, C, and T bases that make up a particular gene.

4. How do viruses cause mutations?

Any virus that incorporates itself into the DNA of a cell by replacing a section of the host DNA with the virus DNA. This can cause amino acids to be made in a different sequence, or entirely different ones that would otherwise be present at from particular segment of the DNA.

5. List three examples of environmental mutagens.

Cigarette smoke, radiation from X rays or UV rays, pollutants such as mercury, and even household chemicals are examples of environmental mutagens that can cause mutations.

3. What is the difference between a neutral mutation and a negative mutation?

Small changes in the sequence of bases can also cause a harmful or negative mutation. Negative mutations reduce the probability that organisms with the mutation will produce offspring or survive in their environment. The change caused by the mutation does not increase or decrease the survival rate of the organism. This type of mutation, which does not affect the organism, is called a neutral mutation. The gene mutation that results in the white coat colour of the Spirit Bear is considered to be a neutral mutation. This mutation neither increases nor decreases the survival rate of the Spirit Bear.

1. Why is the Spirit Bear white?

The Spirit Bear is the result of a gene mutation. Both parents must have this altered gene in order to produce a white bear, and the bear must receive both copies of the gene.