1. Mutations
Learning Goal: To learn about what the causes, types and effects of mutations.
Success Criteria:
I know I am succeeding when I can…
explain that a mutation is a change to the genetic code of an allele
explain the causes of mutations
explain how mutations can be inherited
describe how mutations affect the phenotype of an affected individual
Why do we resemble our parents? (We resemble our parents because we inherit traits from them.) 2. Why does asexual reproduction result in genetic clones? (During asexual reproduction, the organism makes a copy of itself without combining its genes with those from another organism. The offspring are a genetic copy of the single parent.) 3. Why are the offspring of sexual reproduction not genetically identical to either parent? (During sexual reproduction, genes from two individuals combine to produce offspring with new combinations of genes.)

2. Mutations
recall… a mutation is a change in the genetic code of an allele
mutations can be induced by environmental agents such as damaging radiation and certain chemicals, or can be spontaneous resulting from errors during cell division
a mutation may have a positive effect, a negative effect, or no effect
Some gene mutations result in the new cell dying and being recycled
sometimes cells carrying mutations survive and replicate
most mutations occur in parts of the DNA that do not code for genes
many mutations that do occur are immediately corrected during the copying process
as organisms age, mistakes during mitosis occur more frequently and can lead to diseases such as cancer

3. Inheriting Mutations
mutations that occur in body cells (autosomes) are not passed on to offspring and therefore cannot be inherited
mutations that occur in sex cells (gametes) can be passed on to offspring
DNA that mutates in an egg or the sperm that fertilizes it becomes part of the DNA of the zygote
this means that the new individual will have a copy of the mutation in every cell of its body and will be able to pass on the mutation to future generations
If the mutation is dominant, it could be expressed phenotypically in the first generation (as with Huntington’s disease). If a mutation is recessive, it will likely not be expressed for many generations until, by chance, two individuals with the same mutation produce a homozygous recessive mutation in their offspring. Consider the CFTR (cystic fibrosis transmembrane conductance regulator) allele that causes cystic fibrosis. There are various forms of this defective gene, but each CFTR allele was first created by a mutation event in the DNA of a sex cell from a previous generation.

4. Types of Mutations
chromosome mutation: an error that involves an entire chromosome or a large part of a chromosome
examples are non-disjunction, deletions, insertions, or inversions (flipping) of entire portions of a chromosome
In the 1920s, Phoebus Levene discovered that DNA had three main components:
About 3 billion pairs of nucleotides make up the human genome.

5. Types of Mutations Cont’d…
point mutation: a change in single base pair
results from a failure by the replicating cell to copy the genetic information accurately
there are three major point mutations
In the 1920s, Phoebus Levene discovered that DNA had three main components:
About 3 billion pairs of nucleotides make up the human genome.

6. Types of Mutations Cont’d…
base-pair substitutions: one nitrogenous base is accidentally replaced with a different base .
In the 1920s, Phoebus Levene discovered that DNA had three main components:
About 3 billion pairs of nucleotides make up the human genome.

7. Types of Mutations Cont’d…
insertions: one or more nitrogenous bases are inserted during the copying process
In the 1920s, Phoebus Levene discovered that DNA had three main components:
About 3 billion pairs of nucleotides make up the human genome.

8. Types of Mutations Cont’d…
deletions: one or more nitrogenous bases are deleted during the copying process
In the 1920s, Phoebus Levene discovered that DNA had three main components:
About 3 billion pairs of nucleotides make up the human genome.

9. Types of Mutations Cont’d…
in each case the sequence of nucleotides is altered
ribosomes assemble proteins (which cause our traits) based on the sequence of nucleotides
if a change is made in the sequence of nucleotides, the ribosomes will read an altered sequence and assemble a different protein
In the 1920s, Phoebus Levene discovered that DNA had three main components:
About 3 billion pairs of nucleotides make up the human genome.

10. Activity: Name that Mutation!
Purpose: To model the different types of point mutations.
Materials
cue cards and markers
Procedure
write either an A, T, C, or G on each of the 8 cards provided
create DNA sequences with the cards representing genes
take turns altering the sequences in different ways and name which kind of mutation that has been simulated
complete the table below
Observations
In the 1920s, Phoebus Levene discovered that DNA had three main components:
About 3 billion pairs of nucleotides make up the human genome.
Original DNA Sequence
Mutated DNA
Sequence
Type of Mutation

11. Homework read pages 234-239 in your text answer 6.2 questions #1-7
Centrioles are involved in the formation and organization of spindle fibres, which attach to the chromosomes during cell division. The centromere helps anchor the chromosomes to the spindle fibres