Download mutations

Mutations (p. 307)
Mutations are changes in the genetic
material.
Mutations may be genetic mutations or
chromosomal mutations.
Genetic Mutations occur in the “code”
on DNA or mRNA
• Mistakes in
– copying the DNA :
• Inserting the wrong nucleotide
• Skipping or adding a base when a new
strand is assembled.
There are 2 general types of genetic mutations.
1.
Point Mutations
• Involve only one or a few nucleotides.
• Occur at a single point on the sequence.
• Are substitutions.
Substitution:
THE FAT CAT ATE THE RAT
THE TAT CAT ATE THE RAT
2. Frameshift Mutations
• Involve the insertion or deletion of a
nucleotide
• The resulting shift causes every grouping of
three bases after the mutation to be different.
Deletion:
THE FAT CAT ATE THE RAT
THE ATC ATA TET HER AT
Insertion:
THE FAT CAT ATE THE RAT
THE FFA TCA TAT ETH ETA T
Are these
a) point mutations or frameshift mutations?
b) substitutions, deletions or insertions?
1. THE FAT CTA TER AT
2. THE FAT CAA ATE THE RAT
3. THE EFA TCA TAT ETH ERA T
Gene Mutations
• So, gene mutations result from changes in a
single gene.
• They may be point mutation (substitution) or
frameshift mutations (insertions or deletions).
• They may be passed on to the next cellular
generation. HOW?
• Depending on which gene they effect they
may cause no obvious problem or they may be
devastating. (What would happen if there was
a frameshift mutation in the gene that codes
for the production of DNA polymerase?)
Chromosomal mutations (p. 308)
• Chromosomal mutations
involve changes in the
number or structure of
chromosomes.
• Such mutations may
change the locations of
genes on a chromosome
and may even change the
number of copies of some
genes available to the
organism.
Four types (p. 308):
• Deletions
– The loss of all or part of a chromosome
• Duplications
– Extra copies of the chromosome
• Inversions
– Reversal of the direction of part of the
chromosome
• Translocations
– Part of one chromosome breaks off and attaches
to another (ie. 13 to 14)
Chromosomal mutations
• http://www.youtube.com/watch?v=XAGxp9j5
rtc
Chromosomal Disorders
• Non-disjunction: when this occurs,
abnormal numbers of chromosomes may
find their way into gametes, and a disorder
of chromosome numbers may result.
Nondisjunction
Section 14-2
Homologous
chromosomes
fail to separate
Meiosis I:
Nondisjunction
Meiosis II
Go to
Section:
Examples of
Non-Disjunction Disorders
• Down’s Syndrome
• XXY
• Klinefelter’s
• Turner’s Syndrome
Gene regulation
• For Monday, read pages 309 to 312 in your
text.