CMMB 403 Final Exam Actual Questions and Answers with complete solution

CMMB 403 Final Exam Actual Questions and Answers with complete solution 72 hours (8 cells) (BEFORE BLASTOCYST STAGE) - answerwhat is the human MZT Mid-blastula transition/maternal-zygotic transition - answerwhen the transcription of zygotic genes begins and maternal mRNAs are degraded, the cell cycle lengthens, gap stages are added (before is only M and S) and the synchronicity of cell division is lost. - embryo runs on maternal resources (mRNAs and proteins in the egg @ time of fertilization) until this. is when maternal effect genes are turned off. gap genes - answerorganize cells into groups of segments along anterior-posterior axis - are activated OR repressed by MEG products expressed from the zygotic genome (after MZT) and have broad expression domains - divide embryo into regions about 2 segments wide - when lose function causes large gaps in embryo where multiple segments lost, missing several segments in a row - they have 1 or 2 broad stripes of expression and define boundaries in the early embryo - are ZYGOTICALLY expressed - ex: Kruppel maternal effect genes - answerA gene that, when mutant in the mother, results in a mutant phenotype in the offspring, regardless of the genotype - mRNAs deposited in oocyte set up early polarity translated at fertilization - dads genes do not matter for this - create the anterior/posterior axis (cytoplasmic polarity) through bicoid and nanos that form morphogen gradients possible due to syncytium and are incorporated into cells during cellularization pair-rule genes - answerorganize cells into individual segments/ divide the embryo into segment-sized units along the anterior/posterior axis - are activated OR repressed by products of gap genes - helps to define the spatial domains of the homeotic genes - expressed at ONSET of cellularization - have 7 stripes of expression - miss portions of every other segments and may delete boundaries or reduce segment numbers - when mutated have half as many segments and result in only 7 stripes instead of 14 and - ex: fushi tarazu and even skipped homeotic genes - answerGenes that determine basic features of where a body part is - define the identities of each of the segments - their expression domain is correlated with where they are on the chromosome - are all TFs that regulate segment specific genes - have vertebrate homologs! segment polarity genes - answeractivated by pair rule gene products after cellularization, give each individual segment its polarity - have 14 stripes of expression - when mutated polarity disrupted in each segment (segment number doesn't change will get 14) - encode for members of shh and wnt pathways maternal effect - answerwhich gene is transcribed BEFORE and upon fertilization gap - answerwhich genes are transcribed after fertilization but before cellularization and the MZT pair rule - answerwhat genes are expressed at the onset of cellularization/just before - with the MZT segment polarity - answerwhat genes are expressed after cellularization and the MZT 1 or 2 - answerhow many stripes of expression do gap genes have (broad) 7 - answerhow many stripes of expression do pair rule genes have 14 - answerhow many stripes of expression do segment-polarity genes have Parasegments - answertransient subdivisions that occur in the Drosophila embryo prior to the formation of segments - are off register by one half from those of the segments, is made up of the cells in the posterior compartment of one segment and the anterior compartment of the next segment. the expression patterns of early segmentation genes are at THESE boundaries - is the "fundamental unit of embryonic expression" kruppel - answergap gene expressed in parasegments 4-6, is repressed by hunchback, if mutated will be missing several segments in a row (4-6ish) fushi tarazu (ftz) - answerpair rule gene in drosophila that is expressed in even # parasegments, if mutated results in no boundaries btw parasegments and reduced (by half) segment number from 14 to 7 even-skipped (eve) - answerpair rule gene in drosophila that is expressed in ODD # parasegments, if mutated results in no parasegment boundaries and reduced segment number from 14 to 7 engrailed (en) - answersegment polarity gene expressed in cells w high [ ] of either even skipped or fushi tarazu proteins, is a hedgehog pathway regulator that marks the anterior compartment of each parasegment (which is also the posterior part of each segment) - this reinforces parasegment boundaries - is a TRANSCRIPTION FACTOR so NOT secreted outside cells - allows polarized ventral denticle patterns wingless (wg) - answersegment polarity gene expressed transcribed when neither even skipped (eve) or fushi tarazu (ftz) gene are a