發布於 2018-01-11
觀看次數: 105
  • 01:24 1.
    Chromosome Mutations: Variation in Chromosome Number and Arrangement
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    Slide 2
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    Chromosome mutations (aberrations)
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    Variations in chromosome number are known as aneuploidy when an organism gains or loses one or more chromosomes and has other than an exact multiple of the haploid set (Table 8.1)In euploidy, complete haploid sets of chromosomes are presentPolyploidy occu
  • 07:23 5.
    Slide 5
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    Chromosomal variation can arise from nondisjunction, in which chromosomes or chromatids fail to disjoin and move to opposite poles during meiosis I or II (Figure 8.1)Variations in chromosome number are known as aneuploidy when an organism gains or loses o
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    Slide 7
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    Slide 8
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    Monosomy
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    Trisomy
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    Aneuploidy in Sex Chromosomes
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    Down syndrome (Tri-21)
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    Down syndrome is usually a result of nondisjunction of the maternal chromosome 21 during meiosisIt shows an increased incidence with increasing maternal age
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    Genetic counseling is recommended for women who become pregnant late in their reproductive yearsDiagnostic testing—amniocentesis or chorionic villus sampling (CVS)—may be recommended
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    Other examples of trisomy syndromes are Patau syndrome (trisomy 13) (Figure 8.5) and Edwards syndrome (trisomy 18)Trisomies are often found in spontaneously aborted fetuses, but monosomies are notThis suggests that monosomic gametes may be very functional
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    Slide 16
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    Slide 17
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    Slide 17
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    The naming of polyploids is based on the number of sets of chromosomes found: a triploid has 3n chromosomesa tetraploid has 4n chromosomesa pentaploid has 5n chromosomesand so forthInfrequent in many animal species but well know in lizards, amphibians, an
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    Slide 19
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    Autopolyploidy
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    Allopolyploidy
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    Slide 22
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    Allopolyploidy
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    Autopolyploidy
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    Slide 19
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    Autopolyploidy
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    Allopolyploidy
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    Slide 22
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    A classical example of amphidiploidy in plants is the cultivated species of American cotton, Gossypium (Fig. 8-9) 26 pairs of chromosomes- 13 large, and 13 smallOld world cotton-13 pairs of large chromosomes; wild American cotton- 13 small chromosomeJ. O
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    Slide 24
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    A classical example of amphidiploidy in plants is the cultivated species of American cotton, Gossypium (Fig. 8-9) 26 pairs of chromosomes- 13 large, and 13 smallOld world cotton-13 pairs of large chromosomes; wild American cotton- 13 small chromosomeJ. O
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    Slide 22
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    A classical example of amphidiploidy in plants is the cultivated species of American cotton, Gossypium (Fig. 8-9) 26 pairs of chromosomes- 13 large, and 13 smallOld world cotton-13 pairs of large chromosomes; wild American cotton- 13 small chromosomeJ. O
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    Slide 24
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    Amphidiploidys often exhibits traits of both parental speciesRadish (Raphanus sativus; 18R) + cabbage (Brassica oleracea; 18B)  hybird (9R + 9B) treated with colchicine  fertile amphidiploidy (18R +18B) –root like cabbage; shoot like radish radish cabb
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    A much more successful commercial hybridization uses the grasses wheat and ryeWheat (diploids 2n = 14; cultivated autopolyploids, tetraploid 4n, and hexaploid 6n)Rye (diploids 2n = 14)Wheat (4n) + rye (2n)  Triticale (6n, new genus)--- high-protein conte
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    Slide 28
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    Rearrangements of chromosome segments include: Deletions缺失Duplications複本Inversions反向nonreciprocal translocations易位reciprocal translocations (Figure 8.10)
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    Slide 30
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    Slide 31
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    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 occurnear one end (terminal deletion) orfrom the interior of the chromosome (intercalary deletion)
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    For synapsis to occur between a chromosome with a large intercalary deletion and a normal complete homolog, the unpaired region of the normal homolog must loop out of the linear structure into a deletion or compensation loop
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    Deletion Loop in Polytene Chromosomes of Drosophila
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    Polytene chromosome of Drosophila melanogaster
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    Deletion Loop in Polytene Chromosomes of Drosophila
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    For synapsis to occur between a chromosome with a large intercalary deletion and a normal complete homolog, the unpaired region of the normal homolog must loop out of the linear structure into a deletion or compensation loop
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    Deletion Loop in Polytene Chromosomes of Drosophila
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    Polytene chromosome of Drosophila melanogaster
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    Slide 36
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    Polytene chromosome of Drosophila melanogaster
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    Slide 36
  • 00:02 53.
    Cri-du-chat results from a segmental deletion of a small terminal portion of the short arm of chromosome 5Microcephaly, congenital heart disease, and severe mentally retardation
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    Slide 36
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    Cri-du-chat results from a segmental deletion of a small terminal portion of the short arm of chromosome 5Microcephaly, congenital heart disease, and severe mentally retardation
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    Slide 38
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    Duplications arise as the result of unequal crossing over during meiosis or through a replication error prior to meiosis
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    Bar Eye in Drosophila
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    Unequal Crossover Increases Number of Duplications of Bar Gene in Drosophila
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    Gene duplication may play a role in evolution This hypothesis is supported by the discovery of genes that have a substantial amount of their DNA sequence in common, but whose gene products are distinctOther support includes the presence of gene families,
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    Gene family
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    Slide 44
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    An inversion involves a rearrangement of the linear gene sequence rather than the loss of genetic informationIn an inversion, a segment of a chromosome is turned around 180° within a chromosome
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    An inversion requires two breaks in the chromosome and subsequent reinsertion of the inverted segmentAn inversion may arise from chromosomal looping
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    A paracentric inversion does not change the relative lengths of the two arms of a chromosomeA pericentric inversion, which includes the centromere, does change the relative lengths of the two arms of a chromosome
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    Synapsis of inverted chromosomes requires an inversion loop
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    Slide 49
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    Slide 50
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    Slide 49
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    Slide 50
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    Slide 51
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    Translocation is a movement of a chromosomal segment to a new location in the genomeA reciprocal translocationinvolves the exchange of segments between two nonhomologous chromosomeshas an unusual synapsis configuration during meiosisFigure 8.17 shows two
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    Slide 53
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    Robertsonian translocation
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    Slide 55
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    Slide 56
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chromosome-mutation
3:28:37, 發布於 2018-01-11 by 呂佳樺