BIOL 1411 1st Edition Lecture 27Outline of Last Lecture I. Eukaryotic Gene Expression Outline of Current Lecture I. Developmental Genetics & MutationsLecture Developmental Genetics- Pattern formation: the process that results in the spatial organization of tissueso Linked with morphogenesiso Programmed cell death- apoptosis- is also important. Many cells and structures form and then disappear during development. In developing human embryos, connective tissue links the fingers and toes. Later, the cells between the digits die. - Morphogen gradients provide spatial information for pattern formationo Fate of a cell is often determined by where the cell iso Positional information come in the form a type of inducer, a morphogen, which diffuses from one group of cells to another, setting up a concentration gradient- Shh- sonic hedge hog, a morphogen - Pattern formation in drosophila melanogaster o the adult fruit fly drosophila melanogaster has a segmented body: head, thorax, and abdomen, each made of several segments established in the embryo- Segment identity in drosophilao Specification of body regions begins already when a female drosophila makes hereggs= maternal effect geneso A series of embryonic genes are turned on and define the position of each cell in a segment relative to these axes= segmentation geneso The hox genes control the ultimate identity of each body part (antenna, eye, leg, wing) Genes in each stop code for transcription factors that control synthesis of later-acting transcription factors: a transcriptional cascade- Segment identity in drosophilao The maternal effect genes regulate expression of segmentation gene which define segment number and orientation of each segmentThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Three classes of genes act in sequence: Gap genes organize broad areas Pair rule genes divide embryo into units of two segments each Segment polarity genes determine boundaries and anterior-posterior organization in individual segments o Hox Genes Are expressed in different combinations along the length of the embryo. They determine the morphology of each segment Are in two clusters, ordered the same as their spatial expression in the embryo Clues to hox gene function came from homeotic mutants; mutants with mis- regulation of gene expression Hox genes are present in all animals including humans All hox genes encode highly similar DNA-binding proteins - Mutationso Mutations occur in two types: Somatic mutations- occur in somatic cells- passed on by mitosis but not tosexually produced offspring Germ line mutations- occur in germ line cells, the cells that give rise to gametes. A gamete passes a mutation on at fertilization A genetic mutation- is a change in the nucleotide sequence of DNA that istransmitted to the next generation o Relationships between mutations and gene function Silent mutations- do not change polypeptide sequence, thus do not affectprotein function Loss of function mutations- affect protein function and may lead to structural proteins or enzymes that no longer work- almost always recessive Gain of function mutations- lead to a protein with altered function Conditional mutations- cause phenotypes under restrictive conditions butare not detectable le under permissive conditions o Classification of mutations( at the level of DNA sequence) Point mutation- results from the gain, loss, or substitution of a single basepair of DNA Small indels- insertions or deletions of a few to hundreds of base pairs of DNA Chromosomal mutations are more extensive- may change the position of genes or cause multiple genes in a DNA segment to be duplicated or
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