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

SpontaneousProblem arises in DNA replication or gamete formation.

Ex: Strand slippage

InducedCaused 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 anotherFor 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

http://www.youtube.com/watch?v=OS1F54RFD3M

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