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Fig. 25.2
Tortoiseshell Cat--gene expression
--only females (X-linked)
“Stormy”
Gene Mutations--any change in gene sequence--
HOW DO THEY HAPPEN??
Errors in Replication: rare; DNA Polymerase “proofreads” and corrects mistakes
Mutagens: low rate; environmental influences (UV radiation, certain chemicals); DNA repair enzymes fix damage
Transposons: “jumping genes”; specific sequences of DNA that can change locations on chromosomes
FIG. 24.16
Transposons
Indian Corn
Types of Mutations
•FRAMESHIFT--insertion or deletion of a nucleotide; changes how the triplet code is read;
•THE CAT ATE THE RAT•THE ATA TET HER AT (“C” REMOVED)
•POINT MUTATION--substitution of one nucleotide for another
silent--codes for same amino acidnonsense--codes for “stop”missense--changes amino acid and shape
FIG. 26.13
Sickle Cell Anemia
•Point Mutation(single nucleotide)
•Changes shape ofhemoglobin (HB)
•HB forms stiff rods•Can’t carry O2
Fig. 26.2
Nondisjunction in Meiosis=change in chromosome #
3 chromosomes
Fig. 26.1
EXTRA CHROMOSOME--Trisomy 21
•Down Syndrome
•Nondisjunction
•Affects all cells
Fig. 26.3.b1
TRISOMY 21-Gart gene
Gart gene
Fig. 26.4
XO XXY
TURNER SYNDROME KLINEFELTER SYNDROME
Abnormal Sex Chromosome Number
FIG. 26
Muscular Dystrophy--X-linked
Fig. 26.5
Gene Deletion--Williams Syndrome
Fig. 26.6
Duplication and Inversion--”inv dup 15” syndrome