DNA Mutations

Mutations A mutation is a permanent change in DNA. Since DNA determines all aspects of an organism, even small changes can have big effects on the organism. Some mutations alter one gene while some alter an entire chromosome.

Table Talk! Talk to your neighbor for 2 minutes about the following question: What kinds of problems do you think a DNA mutation might cause? Do you think they could be life threatening problems?

DNA code is like a recipe, remember? Ingredients 2 sticks of unsalted butter 1 cup light brown sugar 1/3 cup granulated sugar 2 large eggs 2 teaspoons vanilla extract 2 1/2 cups all-purpose flour 1 teaspoon baking powder 1 teaspoon baking soda 3/4 teaspoon salt 2 cups milk chocolate chips 1. Preheat the oven to 350 degrees Fahrenheit 2. Whisk together all ingredients in a separate mixing bowl. Stir in the chocolate chips. Portion 2 tablespoons of dough for each cookie and roll together to form a ball, spacing the dough balls 2 inches apart on the baking sheet. 3. Bake until the edges just start to brown, 12 to 14 minutes. Transfer to a wire rack to cool.

General Types of Mutations Spontaneous Problem arises in DNA replication or gamete formation. Ex: Strand slippage Induced Caused by our environment causes mutation Ex: Cigarettes, Radiation, Chemicals

Gene Mutations 1. Point Mutations – Mutations that occur in one nucleotide – Substitution: When one nucleotide is substituted for another For example: C-G  A-T

Insertions and Deletions 1. Deletion: when a nucleotide is removed (CGC  CC) 2. Insertion: when a nucleotide is added (CGC  CGAC)

Examples

Table Talk! Talk to your neighbor about what kind of mutation this is, and how you know. What is the result? ACG CCG UAU GUG GGC UAU CUC Thr Pro Tyr Val Gly Tyr Leu ACG CCG UAU GAG GGC UAU CUC Thr Pro Tyr Glu Gly Tyr Leu

Frameshift Mutations When an insertion or deletion causes the “reading frame” to shift Since nucleotides are read in groups of three (codons), a reading frame shift causes all of the following amino acids to be changed ATG GAA GCA CGT Met Glu Ala Gly ATG AAG CAC GT Met Lys His

Frameshift Mutation 3M

Chromosomal Mutations Changes in the number or structure of chromosomes 4 types: – Deletion (1 or more genes are deleted) – Duplication (1 or more genes have two copies) – Inversion ( the location of the genes is switched) – ABCD  DCBA – Translocation (one segment of the chromosome breaks off and attaches to another chromosome

The Good and The Bad Good: – Mutations provide genetic variation in species which increase their chances of survival – Some mutations can fix genetic problems if they alter a diseased gene and make it normal – EX. Changes in the gene for bone density can cause individuals to have increased bone density

The Good and The Bad Bad: – Many mutations cause genetic diseases – Cancer is usually caused by mutations – Down Syndrome is caused by a chromosomal mutation where an individual has two copies of chromosome 21

How do mutations occur? Two ways: – Given to offspring by parent – Acquired during the organism’s lifetime UV radiation from the sun Problems during DNA replication/ cell division Tobacco Chemicals