Lecture 19-Human Genetics

Lecture 19-Human Genetics - Lecture 19: Human Genetics...

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Lecture 19: Human Genetics Thursday, Dec 1, 2011 Human genetics and synthesis of concepts : 1. Identifying genetic disease genes: Cystic Fibrosis 3. Identifying cancer genes: Retinoblastoma 5. An example of unexpected human genetics 4. Familial genetics (Will cover more human genetics next week, Dec 8) Homework 4 is due Tuesday, Dec 6 1 Reading Cystic fibrosis: Hartwell, p. 21, 137 Retinoblastoma and Mitotic recombination: Hartwell, pp. 148; 598- 599
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Some key points about the mouse model Because they are mammals, mice can be used to study many aspects of human development and disease that are common only to placenta-bearing mammals. Conserved synteny is another valuable aspect. Cleavage stage cells are totipotent. (This equivalency of cleavage stage cells allows for targeted gene replacement by the addition of transformed ES cells to non-transformed ES cells, giving rise to chimeras.) Early development is very different from that of C. elegans and Drosophila . (Half a nematode embryo or half a fly embryo can never give rise to a whole animal.) 2
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A major goal of human genetics is to identify the genes responsible for genetic diseases 3
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Cystic Fibrosis: example of a disease gene identified by positional cloning Pedigree analysis 4 Fig. 2.22
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1989: Mapping CF and identifying the CF gene 5 1. Obtained genetic linkage to molecular markers (found a marker, D7S15, that co- segregated with CF ) 2. Narrowed the gene region to ~500 kb 3. Constructed a physical map of the 500 kb region 4. Identified conserved sequences (potential coding sequences) in the region by Southern blotting 5. Identified coding sequences by hybridization to a cDNA library
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Gene product responsible for cystic fibrosis disease: CFTR 6 Fig B, page 21 Several hundred different alleles have been identified A common mutation in 70% of cases is a deletion of a single amino acid, phenylalanine, at position 508 in the CFTR protein CTFR: Cystic fibrosis transmembrane conductance regulator
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Having the CFTR gene cloned allows for the development of possible treatments, in particular gene therapy Mouse model for CFTR was rescued by gene therapy Cultured cells have been rescued Identification of hundreds of existing mutant alleles allows for genetic testing/screening 7
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Retinoblastoma: example of a cancer gene identified by karyotype analysis Retinoblastoma is the most malignant form of eye cancer in humans Certain families show a predisposition to retinoblastoma 8
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9 http://www.ncbi.nlm.nih.gov/books/NBK9894/ Blue - afflicted with eye cancer Green – no cancer Inheritance pattern of retinoblastoma To identify the genetic basis of this, scientists examined the DNA from these families using karyotype analysis
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The human karyotype (visual depiction of all the chromosomes) Fig. 10.2, Hartwell page 338 10
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FISH method Fig. 10.4, Hartwell page 339 11
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SKY (Spectral Karyotyping) is a 24-color FISH (Fluorescence in situ Hybridization) Fig. 10.3 and 10.4, Hartwell page 339 12
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13 Any clone can be mapping by FISH, but only
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This note was uploaded on 04/03/2012 for the course BSCI 410 taught by Professor Staff during the Spring '08 term at Maryland.

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Lecture 19-Human Genetics - Lecture 19: Human Genetics...

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