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Copyright © 2009 Pearson Education, Inc. PowerPoint ® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino Chapter.

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Presentation on theme: "Copyright © 2009 Pearson Education, Inc. PowerPoint ® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino Chapter."— Presentation transcript:

1 Copyright © 2009 Pearson Education, Inc. PowerPoint ® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino Chapter 8 Chromosome Mutations: Variation in Chromosome Number and Arrangement Lectures by David Kass with contributions from John C. Osterman. Copyright © 2009 Pearson Education, Inc.

2 8.1Specific Terminology Describes Variations in Chromosome Number Aneuploidy Euploidy Polyploidy

3 Copyright © 2009 Pearson Education, Inc. Figure 8.1 Nondisjunction

4 Copyright © 2009 Pearson Education, Inc. 8.2Monosomy, the Loss of a Single Chromosome, May Have Severe Phenotypic Effects

5 Copyright © 2009 Pearson Education, Inc. 8.3Trisomy Involves the Addition of a Chromosome to a Diploid Genome Trisomy (2n + 1 chromosomes) for the sex chromosomes has a less dramatic phenotype than trisomies for autosomes, which are often lethal. Section 8.3

6 Copyright © 2009 Pearson Education, Inc. Figure 8.2 Jimson weed: Datura stramonium

7 Copyright © 2009 Pearson Education, Inc. Down syndrome results from trisomy of chromosome 21. (Figure 8.4) Section 8.3

8 Copyright © 2009 Pearson Education, Inc. Figure 8.5

9 Copyright © 2009 Pearson Education, Inc. Figure 8.6 Patau Syndrome

10 Copyright © 2009 Pearson Education, Inc. Figure 8.7 Edwards Syndrome

11 Copyright © 2009 Pearson Education, Inc. Trisomies are often found in spontaneously aborted fetuses, but monosomies are not. This suggests that monosomic gametes may be functionally impaired. Section 8.3

12 Copyright © 2009 Pearson Education, Inc. 8.4Polyploidy, in Which More Than Two Haploid Sets of Chromosomes Are Present, Is Prevalent in Plants The naming of polyploids is based on the number of sets of chromosomes found: a triploid has 3n chromosomes a tetraploid has 4n chromosomes a pentaploid, 5n chromosomes and so forth Section 8.4

13 Copyright © 2009 Pearson Education, Inc. Polyploidy can originate by: the addition of one or more sets of chromosomes identical to the haploid complement of the same species (autopolyploidy) or the combination of chromosome sets from different species as a consequence of interspecific matings (allopolyploidy) (Figure 8.8) Section 8.4

14 Copyright © 2009 Pearson Education, Inc. Figure 8.8

15 Copyright © 2009 Pearson Education, Inc. 8.5Variation Occurs in the Internal Composition and Arrangement of Chromosomes Rearrangements of chromosome segments include: deletions duplications inversions nonreciprocal translocations reciprocal translocations (Figure 8.13) Section 8.5

16 Copyright © 2009 Pearson Education, Inc. Figure 8.13

17 Copyright © 2009 Pearson Education, Inc. When a chromosome breaks in one or more places and a portion of it is lost, the missing piece is referred to as a deletion (or a deficiency). The deletion can occur: near one end (terminal deletion) or from the interior of the chromosome (intercalary deletion) (Figure 8.14) 8.6A Deletion Is a Missing Region of a Chromosome

18 Copyright © 2009 Pearson Education, Inc. Figure 8.14

19 Copyright © 2009 Pearson Education, Inc. Cri-du-chat results from a segmental deletion of a small terminal portion of the short arm of chromosome 5 (Figure 8.15). Section 8.6

20 Copyright © 2009 Pearson Education, Inc. The type of Notch phenotypic expression of recessive genes in association with a deletion in Drosophila is an example of pseudodominance. Section 8.6

21 Copyright © 2009 Pearson Education, Inc. Duplications arise as the result of unequal crossing over during meiosis or through a replication error prior to meiosis (Figure 8.17). 8.7A Duplication Is a Repeated Segment of the Genetic Material

22 Copyright © 2009 Pearson Education, Inc. Organisms have multiple copies of the ribosomal RNA genes (rDNA). This is an example of gene redundancy. Gene amplification is another mechanism to increase the rRNA. Section 8.7

23 Copyright © 2009 Pearson Education, Inc. The Bar-eye phenotype in Drosophila results from duplication (Figure 8.18).

24 Copyright © 2009 Pearson Education, Inc. 8.8Inversions Rearrange the Linear Gene Sequence An inversion involves a rearrangement of the linear gene sequence rather than the loss of genetic information. In an inversion, a segment of a chromosome is turned around 180° within a chromosome. Section 8.8

25 Copyright © 2009 Pearson Education, Inc. Figure 8.19

26 Copyright © 2009 Pearson Education, Inc. Figure 8.20

27 Copyright © 2009 Pearson Education, Inc. Synapsis of inverted chromosomes requires an inversion loop (Figure 8.21). Section 8.8

28 Copyright © 2009 Pearson Education, Inc. Figure 8.22 shows the effects of a single crossover within an inversion loop for both paracentric and pericentric inversion heterozygotes. For a paracentric inversion crossover: one recombinant chromatid is dicentric (two centromeres) one is acentric (lacking a centromere) Section 8.8

29 Copyright © 2009 Pearson Education, Inc. Figure 8.22

30 Copyright © 2009 Pearson Education, Inc. Translocation - movement of a chromosomal segment to a new location in the genome. Reciprocal Translocation: involves exchange of segments between 2 nonhomologous chromosomes has an unusual synapsis configuration during meiosis 8.9Translocations Alter the Location of Chromosomal Segments in the Genome

31 Copyright © 2009 Pearson Education, Inc. Figure 8.23

32 Copyright © 2009 Pearson Education, Inc. Robertsonian translocation or centric fusion involves breaks at the extreme ends of the short arms of 2 nonhomologous acrocentric chromosomes Section 8.9

33 Copyright © 2009 Pearson Education, Inc. Figure 8.25 Familial Down Syndrome

34 Copyright © 2009 Pearson Education, Inc. 8.10Fragile Sites in Humans Are Susceptible to Chromosome Breakage Fragile sites are more susceptible to chromosome breakage when cells are cultured in the absence of certain chemicals such as folic acid. Section 8.10

35 Copyright © 2009 Pearson Education, Inc. Fragile X syndrome (Martin–Bell syndrome) is the most common form of inherited mental retardation, affecting about 1 in 4000 males and 1 in 8000 females, and is a dominant trait (Figure 8.26). Section 8.10


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