Put your HW in the HW folder. What do all of the following have in
common?
Genetic ChangesChapter 11.3
MUTATIONMUTATION defined as a change in the DNA sequence can be caused by errors in replication,
transcription, cell division, or by external agents
Mutations Reproductive cells
Will be passed down to offspring Embryo may not survive Offspring might be sterile
Body cells Impair cell function Cancer Premature aging
Point Mutation: Single base alteration
What do you see happening?
Sickle cell anemia
Frameshift Mutation A type of point mutation: single base is added or deleted from DNA
How is this different than a point mutation? How is it similar?
Frameshift cont’d If groups of 3 (or multiples of 3) bases is
added or deleted, it will only affect a few amino acids (1 per codon)
If 1, 2, 4 (any non-multiple of 3) is deleted, ALL amino acids will be different from the mutation onward. Causes a change in the reading frame
Cystic fibrosis – affects the lungs, liver, pancreas, small intestine, reproductive organs, and the skin
Chromosomal mutations When there are changes in the chromosome, it
is considered a chromosomal mutation. Part of a chromosome is broken off and lost There are 4 kinds of chromosomal mutations:
Deletions, Insertions, Inversions, Translocations
Break and rejoin incorrectly Nondisjunction
Deletion: Section is lost from a chromosome
Insertion: Section of 1 chromosome is added to another
Inversion: segment of chromosome reverses itself
For each #, what is different between the chromosome on the left to the one on the right?
Translocation: Sections of 2 different chromosomes are swapped
Nondisjunction
Results in a change in the chromosome # in the daughter cells
Polyploidy
Polyploidy in strawberries
Wild type Commercially propagated varieties
Each cell is 1n Each cell is 8n 8 copies of each chromosome!
Polyploidy in Dianthus
More examples: Consider a normal chromosome with genes in alphabetical
order: a b c d e f g h i 1. Deletion: part of the chromosome has been removed: a b c g h
i 2. Dupliction(Insertion): part of the chromosome is duplicated:
a b c d e f d e f g h i3. Inversion: part of the chromosome has been re-inserted in
reverse order: a b c f e d g h i
More examples cont.4. translocation: parts of two non-homologous
chromosomes are joined:
If one normal chromosome is a b c d e f g h i and the other chromosome is u v w x y z,
then a translocation between them would be
a b c d e f x y z and u v w g h i.
Causes of Mutations random, mistake in base pairing mutagens (ex. radiation, chemicals, high
temperature)
Radiation contains energy that can damage or break
apart DNA breaking and reforming of DNA can result in
deletions may convert one base into another or fuse two
bases together
Chemical mutagens include asbestos, benzene, and formaldehyde usually cause substitution mutations
Sources of formaldehyde
DNA repair “Proofreading” is performed by enzymes like
DNA ligase. Such repair mechanisms work very
efficiently, although they are not perfect. Thus, it is still best to avoid situations that
would expose us to mutagens.
HW for 3/13 Due tomorrow:
Worksheet on DNA/RNA and mutations Field trip permission slip and $5
Due Friday: Ch.12 Index Cards
Problem-Solving Lab 11-3 (p. 299) In your groups, answer questions 1-4 on a
blank sheet of paper with everyone’s name on it.
Group with the most correct answers gets 2 bonus points for the day.
You have 7 min – starting now!