Genes and Development Gene theory: controversy whether the material of inheritance was in the nucleus or cytoplasm. Do all cells share the same genome? GENOME EQUIVALENCE ….do differentiated cells undergo any irreversible loss of its genome? Briggs and King (1950) : somatic nuclear transfer Wilmut: mammalian cloning If all cells share the same genome, how do they differentiate into the different cell types? DIFFERENTIAL GENE EXPRESSION. All differentiated cells contain the same DNA. Unused genes are not lost; they retain the potential for being expressed. Only a small percentage of the genome is expressed in each cell, and a portion of the RNA synthesized in the cell is specific for that cell type

4.5 Procedure for transplanting blastula nuclei into activated enucleated Rana pipiens eggs (1)

4.5 Procedure for transplanting blastula nuclei into activated enucleated Rana pipiens eggs (2) This procedure is called somatic nuclear transferred or cloning.

4.6 Percentage of successful nuclear transplants as a function of the developmental age of the donor nucleus

4.7 A clone of Xenopus laevis frogs

4.8 Cloned mammals, whose nuclei came from adult somatic cells

4.9 The kitten “CC” (A) is a clone produced using somatic nuclear transfer from “Rainbow” (B) Many of the clones developed debilitating diseases as they matured. The phenotype of the cloned animal is sometimes not identical to the animal from which the nucleus was derided (due to chromosomal events and the effects of environment).

4.10 Cloning of transgenic mammals to produce protein pharmaceuticals

Differential Gene Expression How do cells become different from one another? Different gene expression: - every cell nucleus contains the complete genome established in the fertilized egg. - the unused genes in differential cells are not destroyed or mutated - only a small percentage of the genome is expressed in each cell, and a portion of the RNA synthesized in each cell is specific for that cell type. Different regions of chromosomes make different, tissue- specific mRNAs based on the differentiated cell type. DNA-RNA hybridization: involves annealing single-stranded pieces of RNA and DNA to allow complementary strands to form double-stranded hybrids.

4.12 The RT-PCR technique for determining whether a particular type of mRNA is present (Part 1)

4.12 The RT-PCR reaction technique for determining whether a particular type of mRNA is present (Part 2)

4.13 Microarray technique (Part 1)

4.13 Microarray technique (Part 2)

4.15 In situ hybridization showing the expression of the Pax6 gene in the developing mouse eye

4.16 Whole-mount in situ hybridization localizing Pax6 mRNA in early chick embryos Pax6 expression: -roof of the brain region that will form the eyes, -in the head ectoderm that will form the lenses; - in a more caudal region of the neural tube; and - in the pancreas.

4.17 Insertion of new DNA into embryonic cells

4.18 Production of transgenic mice (Part 1)

4.18 Production of transgenic mice (Part 2)

4.18 Production of transgenic mice (Part 3)

4.18 Production of transgenic mice (Part 4)

4.19 Technique for gene targeting (Part 1)

4.19 Technique for gene targeting (Part 2)

4.19 Technique for gene targeting (Part 3)

4.20 Morphological analysis of Bmp7 knockout mice (Part 1)

4.20 Morphological analysis of Bmp7 knockout mice (Part 2)

4.21 Use of antisense RNA to examine the roles of genes in development

4.22 The dsRNA-mediated gene silencing procedure

4.23 Injection of dsRNA for E-cadherin into the mouse zygote blocks E-cadherin expression