14.1 Notes-Mutations - Fulton County Schools

Chapter 14.1 Notes
1. What is a mutation? Mutations are not necessarily mistakes -- rather, they are
just changes. These mutations account for the diversity of different human traits
in our human species
2. Why are we so similar as humans (despite some obvious differences)?
Because MOST of those mutations do NOT affect the DNA that actually codes for
proteins. Only ~1.5% of the DNA code in our cells actually code for proteins. So if
we have mutations in the other 98.5% of our DNA, it might not have any effect.
3. Mutagens are environmental factors that can cause mutations
o 2 major categories include radiation and chemicals, might speed up
the rate of mutation in your cells, but there is still a small rate
of mutations that just seem to occur naturally. Some Chemicals
(cigarettes) and drugs can cause mutations.
4. If mutations occur in germ cells, also called sex cells, then the effects could be
passed on to future offspring.
5. Types of mutations:
a. Point mutation- change of a single nucleotide
o Could be a silent mutation, which means what? It has no effect,
has the LEAST effect on a protein's shape and function
o Could change one amino acid in protein
b. Frameshift mutation- an addition or deletion can shift the codons, typically has
the MOST effect on a protein's shape and function
o Could involve additions OR deletions to DNA code
o Why does this usually cause more of a change in protein than a
point mutation? The remaining sequence can be read as different
6. Errors can occur in meiosis, and create gametes with too many or not enough
7. The failure to separate chromosomes is called nondisjunction (Genetics 2 Unit)
o Examples of disorders caused by nondisjunction: Down’s Syndrome,
Turners Syndrome and Klinefelter’s Syndrome.
Chapter 14 Notes
Karyotype: a chart that describes the number of chromosomes, and what they look like
XX = Female, XY = Male
4 types of chromosomal mutations:
1. Deletion – occur when part of a chromosome is left out
2. Insertion – occur when part of a chromatid breaks off and attaches to its
sister chromatid.
3. Inversion – occur when part of one chromosome breaks off and is reinserted
4. Translocation – occur when one chromosome breaks off and is added to a
different chromosome.
Pedigree: diagram that shows the occurrence and appearance of a particular gene and its
ancestors from one generation to the next.
Example: family with Cystic Fibrosis a recessive condition.
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