Copyright © 2009 Pearson Education, Inc. Chapter 8 Chromosome Mutations: Variation in Chromosome Number and Arrangement Copyright © 2009 Pearson Education, Inc.
Table 8.1
Copyright © 2009 Pearson Education, Inc. Figure 8.1 Non-Disjunction
Copyright © 2009 Pearson Education, Inc. Monosomy Results from the loss of one chromosome 2n – 1 Loss of a chromosome in mammals is not tolerated Why do organisms not survive?
Copyright © 2009 Pearson Education, Inc. Trisomy Results from the gain of one chromosome 2n + 1 In many cases, the individual can survive Trisomy is common in plants Jimson Weed
Copyright © 2009 Pearson Education, Inc. Figure 8.2 The 12 Possible Trisomies in Jimson Weed
Copyright © 2009 Pearson Education, Inc. Trisomies in Humans Down Syndrome (47, 21+) Patau Syndrome (47, 13+) Edwards Syndrome (47, 18+)
Copyright © 2009 Pearson Education, Inc. Down Syndrome First reported in in 800 live births Physical, physiological, and mental abnormalities Average life expectancy is around 50 years Can arise through non-disjunction in anaphase I or II 75% are during meiosis I 95% are from errors in ovum formation
Copyright © 2009 Pearson Education, Inc. Figure 8.4 Down Syndrome
Copyright © 2009 Pearson Education, Inc. Figure 8.5
Copyright © 2009 Pearson Education, Inc. Figure 8.6 Patau Syndrome Aka Trisomy 13 1 in 19,000 live births Average survival is 3 months Average age of parents is around 32
Copyright © 2009 Pearson Education, Inc. Figure 8.7 Edwards Syndrome Aka Trisomy 18 1 in 8,000 live births Average survival is 4 months Average maternal age is 34.7 Most infants are females
Copyright © 2009 Pearson Education, Inc. Aneuploidy Statistics David Carr 1971 study of spontaneously aborted fetuses Significant number were because of trisomies Monosomies were rarer Additional findings
Copyright © 2009 Pearson Education, Inc. Polyploidy Occurs when there are more than 2 haploid sets of chromosomes Naming is based on the number of sets Triploidy – 3n Tetraploid – 4n Common in plants, not so common in animals Autopolyploidy vs. Allopolyploidy
Copyright © 2009 Pearson Education, Inc. Figure 8.8 Polyploidy
Copyright © 2009 Pearson Education, Inc. Autopolyploidy Can arise in several ways Autotriploids Autotetraploids Can be induced in the lab by adding colchicine to dividing cells Important to agriculture
Copyright © 2009 Pearson Education, Inc. Figure 8.9 Colchicine Induction
Copyright © 2009 Pearson Education, Inc. Allopolyploidy Results from hybridizing two closely related species Usually can’t reproduce because can’t produce viable gametes Can be induced in the lab using cochicine
Copyright © 2009 Pearson Education, Inc. Figure 8.10
Copyright © 2009 Pearson Education, Inc. Figure 8.11
Copyright © 2009 Pearson Education, Inc. Endopolyploidy Condition in which only some cells are polyploid in an otherwise diploid organism
Copyright © 2009 Pearson Education, Inc. Variation in Internal Composition and Arrangement of Chromosomes Deletions Duplications Inverstions Translocations
Copyright © 2009 Pearson Education, Inc. Deletions A missing region of the chromosome
Copyright © 2009 Pearson Education, Inc. Figure 8.13a Deletions A missing region of a chromosome Terminal deletion Intercalary deletion
Copyright © 2009 Pearson Education, Inc. Figure 8.14
Copyright © 2009 Pearson Education, Inc. Figure 8.15 Cri du Chat Syndrome
Copyright © 2009 Pearson Education, Inc. Figure 8.13b Duplications The presence of any part of the genetic material more than once in a genome Results from misalignment during synapse Three interesting aspects of duplications Result in gene redundancy May produce phenotypic variation Important for evolution
Copyright © 2009 Pearson Education, Inc. Figure 8.17
Copyright © 2009 Pearson Education, Inc. Figure 8.13b Duplications are important in evolution Mutations generally can’t happen in genes critical to survival Why? How could gene duplication allow this to happen?
Copyright © 2009 Pearson Education, Inc. Figure 8.13b Inversions Occurs when the genetic information within a chromosome gets flipped No loss or gain, just rearrangement Paracentric vs Pericentric The individual is usually not affected But might have problems producing gametes
Copyright © 2009 Pearson Education, Inc. Figure 8.19
Copyright © 2009 Pearson Education, Inc. Figure 8.20
Copyright © 2009 Pearson Education, Inc. Figure 8.21 No Crossing Over
Copyright © 2009 Pearson Education, Inc. Figure 8.22
Copyright © 2009 Pearson Education, Inc. Figure 8.13d Translocations
Copyright © 2009 Pearson Education, Inc. Figure 8.25 Familial Down Syndrome
Copyright © 2009 Pearson Education, Inc. Figure 8.26 Fragile Sites