1. Mutations Mutation- a change in the DNA nucleotide sequence
Mutations can be silent, cause subtle, or dramatic effects on observed traits in individuals

2. How does your DNA determine your traits?
mRNA
protein
Observed trait
transcription
translation
protein function
(enzyme activity)
Remember:
Traits are determined by the functions of proteins
Protein function is determined by protein shape
Protein shape is determined by amino acid sequence

3. Mutations can change the amino acid sequences of proteins
DNA sequence: T A C C G A G A T T C A
mRNA sequence: A U G G C U C U A A G U
amino acid sequence: Met -- Ala -- Leu -- Ser
mRNA sequence: A U G G C U A U A A G U
amino acid sequence: Met -- Ala -- Iso -- Ser T

4. How does this mutation change the amino acid sequence?
(Original)
DNA sequence: A A T G C A T A T G C A
mRNA sequence: U U A C G U A U A C G U
amino acid sequence: Leu -- Arg -- Ile -- Arg
(Mutated)
DNA sequence: A A T T C A T A T G C A
mRNA sequence: U U A A G U A U A C G U
amino acid sequence: Leu -- Ser -- Ile -- Arg

5. 3 types of mutations T Substitution Insertion Deletion
T A C C G A G A T T C A
Substituting one nucleotide for another.
T A C C G A T
G A T T C A
Inserting one or more nucleotides
T A C C G A
G A T T C A
Deleting one or more nucleotides

6. Your Turn
Complete the “Mutations practice” worksheet. You will learn how some mutations can affect the amino acid sequence of proteins
Consider how severe of an effect each mutation would have on the ability of the protein to function.

7. Question:
We’ve studied transcription, translation, and replication. A mistake in which of these processes would result in a permanent mutation?

8. Which type of mutations had the biggest effect on the protein sequence
Which type of mutations had the biggest effect on the protein sequence? WHY?
Which type of mutations had the smallest effect on the protein sequence? WHY?
Which examples would you predict to have the biggest effects on a trait? WHY?
Which examples would you predict to have the smallest effects on a trait? WHY?

9. Different types of mutations happen
Substitution
Insertion
Deletion T
T A C C G A G A T T C A
T A C C G A T
G A T T C A
T A C C G A
G A T T C A

10. Frameshift mutations
One or more than one nucleotide can be added or deleted with insertion and deletion mutations.
If the number of nucleotides is not a multiple of 3, it is called a frameshift mutation.
Why do we call this a frameshift mutation?
Can substitution mutations cause frameshifts? Explain why or why not.
Students discuss in partners/small group
Discuss briefly as class
Students write answers INDIVIDUALLY (no talking answers to question on notecard and pass in for assessment)

11. Consequences of mutations…
If a mutation in sperm or egg DNA is not corrected, the new sequence of DNA is passed on to offspring.
Over generations, more mutations accumulate.
As a result, differences occur between people’s DNA sequences!

12. How much variation in DNA exists between 2 people?
Hemoglobin (beta) gene sequence from person A

13. How much variation in DNA exists between 2 people?
Hemoglobin (beta) gene sequence from person B

14. How much variation in DNA exists between 2 people?
About 1 in every 1,000 nucleotides is different between 2 people
(0.1% difference means 99.9% identical)
We have about 3 billion nucleotides in all, so that means there are about 3 million nucleotide differences between 2 people

15. What is the observed effect of mutations?
No Effect
(think about it: are there 3 million differences between 2 people?)
Why?
Some mutations code for the same amino acid
Most mutations are in sequences of DNA between genes.
Variation – there are a variety of traits in a population.

16. Genetic diseases
Many alleles are harmless, but some can cause specific diseases.
To determine whether a disease is genetic, we trace the family history of a disease by creating a type of family tree called a pedigree.
One disease caused by a specific mutation is sickle cell anemia