Transcript DNA Mutations - Cloudfront.net

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
Induced
Problem arises in DNA
replication or gamete
formation.
Caused by our
environment causes
mutation
Ex: Strand slippage
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
http://www.youtube.com/watch?v=OS1F54RFD
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