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18 Cards in this Set
- Front
- Back
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3 postulates of differential gene expression
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1)Every cell nucleus contains the complete genome established in the fertilized egg. In molecular terms, the DNA of all differentiated cells are identical.
2)The unused genes in differentiated cells are not destroyed or mutated, and they retain the potential for being expressed. 3)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. |
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Genetics vs. Embryology
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Genetics: “transmission of traits”
Embryology: “expression of traits” |
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Thomas Hunt Morgan
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Morgan believed that nuclear chromosomes were responsible for inheritance of genes, and that the cytoplasm controlled development.
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Edmund Beecher Wilson
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Wilson felt that the nucleus contained the instructions for development.
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What Causes Angelman Syndrome?
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AS is due to abnormal expression of a group of genes on chromosome 15. It is likely that at least one of these genes controls development of the brain, especially the parts associated with language, movement and pigmentation. It seems also that some genes influence chemical transmission of messages within the brain.
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Differential gene transcription:
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DNA -> nRNA
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Selective nuclear RNA processing:
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nRNA -> mRNA
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Selective mRNA translation:
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mRNA -> Protein
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Differential protein modification:
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Active protein -> Inactive Protein
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Leader sequence
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the intervening sequences between the initiation sites of transcription and translation, also called the 5’untranslated region (5’UTR), can determine the rate of translation initiation
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Translation initiation site
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(ATG), becomes AUG in the mRNA, Encodes the first amino acid of the protein
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Translational termination codon
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“stop” codon, becomes UAA
in the mRNA The ribosome dissociates at this codon and the protein is released |
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polyadenylation site
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3’ untranslated region(3’UTR), AATAAA
*confers stability to the mRNA *Allows the mRNA to exit the nucleus *Permits the mRNA to be translated into protein |
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poly (A) tail
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The length of the poly(A) tail can regulate the translatability of the
mRNA. Addition of poly(A) residues can make an mRNA translatable, while removing the poly(A) can prevent translation. |
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3 Germ Layers: Ectoderm (outer layer)
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outer surface (epidermal cells of skin)
central nervous system (neuron of brain) neural crest (pigment cell [melanocyte]) |
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3 Germ Layers: Mesoderm (Middle Layer)
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*dorsal (notochord)
*paraxial (bone tissue) *intermediate (tubule cell of the kidney) *lateral (red blood cells) *head (facial muscle) |
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3 Germ Layers: Endoderm (Internal layer)
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*digestive tube (stomach cell)
*pharynx (thyroid cell) *respiratory tube (lung cell) |
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Germ Cells
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Male: sperm
Female: egg |
