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8.7 Mutations & Karyotypes (7.4)
Name: __________________________
KEY CONCEPT:
____________________ are changes in DNA that may or may not affect phenotype.
 May occur in __________________________(aren‘t passed to offspring)
 May occur in ______________________ (eggs & sperm) and be passed to offspring
 Mutations lead to ________________ _____________________ because they ___________________ change an
organisms__________________ _________________.
Types of Mutations
Some mutations affect a single gene, while others affect an entire chromosome.
A __________________________________ affects a single gene.
 Many kinds of mutations can occur, especially during replication.
Types of Gene Mutations:
 A ________________________________________ substitutes one nucleotide for another.

Nonsense Mutation: Results in a ____________________________________ and usually a
_________________________________________________
•
A _________________________________________ inserts or deletes a nucleotide in the DNA sequence. Throws
off the reading frame.
Example:
THE CAT ATE THE RAT
THC ATA TET HER AT
Draw an insertion of this same sentence: ___________________________________________
Draw an inversion from the animation: _____________________________________ Describe what happens in an inversion
mutation:
___________________________________ affect many genes and an entire chromosome. Chromosomal mutations may occur
during crossing over/meiosis. (Note: Crossing over is
normal & NOT a mutation itself)
Normal------------>
 Five types of chromosome mutations exist:
___________________________
___________________________
___________________________
___________________________
___________________________
Deletion
 Due to _______________________________
 A __________________ of a chromosome is ______________
Inversion
 Chromosome segment __________________________
 Segment flips around ___________________________
 Segment ___________________________
Translocation
 _________________________ results from the exchange of DNA (piece of one chromosome) segments between
non-homologous chromosomes. Sometimes chromosomes can fuse onto another chromosome.
Nondisjunction
 ____________________ of chromosomes to ____________________ during meiosis
 Causes gamete to have ______________________________________________________
 Can cause “Trisomy” (three copies of the same chromosome in an egg or sperm)

Trisomy 21 (Down syndrome)
Duplication
•
_______________________________________ results from unequal exchange of segments crossing over.
Results in one chromosome having 2 copies of some genes and the other chromosomes having no
copies of those genes.
Mutations may or may not affect phenotype.
1. __________________________________ tend to have a big effect. Many genes are affected.
2. Some _______________________________________ change phenotype by:
– causing a premature stop codon.
– causing a change in protein shape or the active site.
– causing a change in gene regulation.
3. Some gene mutations do not affect phenotype.
 A mutation may be silent because….
– It occurs in a _________________________________________.
– It may not affect protein ______________________ or the __________________________________________.
– Example:
GUC changed to
GUG
Both code for the
amino acid
valine
This would not
affect the protein
being made in
any way
Mutations can be caused by several factors.
1. ________________________ errors can cause mutations.
2. Mutagens, such as _____________________ and ______________________, can cause mutations.
3. Some _________________________________ use mutagenic properties to kill cancer cells.
4. Mutations happen ________________________________
5. Almost all mutations are ____________________________
6. Many mutations are _____________________________by enzymes
7. Some types of __________________________________________ result from __________________________ mutations
8. Some mutations may ________________ an organism’s _______________________(beneficial)
Several methods help map human chromosomes.
• A _______________________ is a picture of all chromosomes in a cell.
X
Y
Karyotypes can show ___________________ in chromosomes.
– _____________________ of part of a chromosome or loss of a chromosome
– ______________________________________ in chromosomes
– _______________ chromosomes or _______________________ of part of a chromosome