do mutations affect a species?)
Ask students, “What is a mutation? Are mutations good or bad?” Take
all student responses without judgment, as you will return to this question
a the end of the lesson
Show student Overhead 1 and tell them, “There are
many types of mutations:
Point mutations: A single nucleotide base being changed.
This type of mutation can affect a gene’s protein
production in several ways.
Missense Mutation: A point mutation that results in a single
amino acid change in a protein.
Nonsense Mutation: A point mutation that can result in
a premature stop codon causing the protein to be shortened.
Silent Mutation: A point mutation that does not cause a
change in the amino acid produced by the protein.
Insertion Mutation: The addition of a DNA base.
Deletion Mutation: The removal of a DNA base.
Frameshift Mutation: Caused by insertion or deletion mutations,
this changes the grouping of nucleotide bases into codons.
Show student Mutation Overhead 2. Ask them to identify
the correct DNA grouping. Look at how many different codons
are used for each protein. Note that some have as many
as six codons and others have only one. Have students explain
why there might be only 1 start, yet 3 stop codons.
Have each student take the correct DNA sentence from Overhead 2 (sentence number
3) and mutate it. They should record both the original strand and the mutation
in their science notebook. After a few minutes, ask for volunteers. They should
write their mutation on the board of overhead, while classmates try to determine
the type of mutation. If it is a point mutation, which of the 3 changes in protein
production occurs? This is the time to drive home the point that mutations are
random. Organisms do not choose to change a letter of the DNA code. The mutations
are just errors that by chance happen to benefit organisms from time to time.
Ask the class to think back over the last few days in science class.
They have talked about DNA, genes, chromosomes, mitosis, meiosis,
heredity, and DNA replication. What similarities and differences
exist in these functions of these processes? Where are the potential
places for mutations? What type of mutations might have affected
human evolution? How?
Have groups discuss these ideas and explain one circumstance where
a mutation might have affected an individual and one where it might
have affected a species.
Can students identify that only errors in gametes affect
Can students correctly identify types of mutations?
Do students understand that mutations are random and
not chosen by individuals?
Have students record concluding thoughts
in their notebooks after reflecting on the day’s