Download How Things Go Wrong

How Things Go Wrong
Explore piece from: The Genetics Learning Center
Modified by: Kirstin Bittel and Rachel Hughes
Remainder by Kirstin Bittel and Rachel Hughes
Time :
Preparation Time :
Materials :
1 class period
5 minutes making overheads
Overhead One
Overhead Two
Abstract
During this lesson students will be able to identify where mutation might occur though discussion
of DNA replication and cell division.
Purpose – To identify when mutation occur and what effect those mutations will have.
Objectives
Students will be able to:1. Differentiate mutations that affect an individual and mutations that affect and entire species.
National Science Education Standard:
Content Area C – The Molecular Basis of Heredity
- Changes in DNA (mutations) occur spontaneously at low rates. Some of these changes make
no difference to the organism, whereas others can change cells and organisms. Only mutations in
germ cells can create the variation that changes an organism's offspring.
Content Area C - Biological Evolution
- Species evolve over time. Evolution is the consequence of the interactions of (1) the potential
for a species to increase its numbers, (2) the genetic variability of offspring due to mutation and
recombination of genes, (3) a finite supply of the resources required for life, and (4) the ensuing
selection by the environment of those offspring better able to survive and leave offspring.
Teacher Background
While some mutations are fatal, many are not. Some mutations affect individuals and other affect
the entire species. Only mutations in gametes (sex cells) have the potential to change a species.
As long as the mutation does not impact the ability to reproduce at least once, it can be passed
down from parent to offspring and remain part of the genetic makeup of a species.
Related and Resource Websites
http://www.gsle.genetics.utah.edu/units/disorders/mutations/mutatedna.cfm
http://www.glse.genetics.utah.edu/units/disorders/sloozeworm/
Activity:
Engage (How 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
Explore
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.
Explain
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.
Expand
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.
Evaluate
Can students identify that only errors in gametes affect a species?
Can students correctly identify types of mutations?
Do students understand that mutations are random and not chosen by individuals?
Homework
Have students record concluding thoughts in their notebooks after reflecting on the day’s events.