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CMMB 403 final exam actual questions and answers with complete solution
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CMMB 403 final exam actual questions and answers with complete solution
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CMMB 403 final exam actual questions and answers 2024-2025 with complete solutionwhat does CRISPR use in order to generate changes in genome? is CRISPR forward or
reverse genetics? Ans- - nuclease
- 20 nucleotide RNA sequence to target specific sites in the genome
- reverse genetics
what is the role of Cas9 in CRISPR Ans- endonuclease that catalyzes double stranded
breaks
what are the two repair paths cells can use to repair double stranded breaks from CRISPR-Cas9 Ans- 1. non-homologous end joining (NHEJ)
- naturally try to repair
- imperfect, creates indels causing frameshift mutation
2. directed homology repair
- sequence homology on 5' and 3' ends to encourage homologous recombination flanking the double stranded breaks
- insert known sequences to try and treat genetic diseases
explain the method of conditional gene inactivation Ans- - make targetting construct in lab
- electroporate construct into embryonic stem cells to target endogenous Shox2 locus
- mice generated by blastocyst injection into ESCs carry loxP sites therefore can delete Shox2
2 components for a conditional knockout mouse Ans- 1. transgenic mice express Cre recombinase in the tissue of interest
2. mice with loxP sites on each side of the gene or region to be deleted
How is CRISPR-Cas9 being used in a patient in the USA to treat sickle cell anemia? Ans- by inactivating an enhancer of the BCL11A gene
(BCL11A gene represses fetal hemoglobin)
how does the BCL11A protein affect global gene expression Ans- it represses fetal hemoglobin gene expression
In what kind of animals is CRISPR good? Ans- any animals for which one cell embryos
are accessible - good for mammals, not chickens
what is the result of CRISPR inactivating Rspo2 in half a frog? Ans- Rspo knockout= limbless
side inactivated by CRISPR had no limb
what are transgenic mice good for?
- how are they made?
- is this targeted?
- what are they not useful for? Ans- good for mis-expressing genes, enhancer reporters, etc.
- generated by pronuclear injection; DNA construct is incorporated randomly into the genome
- not useful for LOF because not targeted
how are knockout mice made?
- is it targeted?
- what kind of species is this successful in? Ans- created by genomic targeting in embryonic stem cells
- DNA construct is targeted to specific sites in the genome by homologous recbomination
- mice then made from pluripotent ES cells
- only successful in mice
what is CRISPR/Cas9 good for?
- what kind of species is it successful in? Ans- efficient RNA-directed targeting in single-cell embryos or cell lines from a broad variety of species
- useful for knockout, introducing changes in genome, corrections, etc. - many species
when does organogenesis occur in human development? Ans- 4th-8th week
what day is the neural plate formed? Ans- day 18
what day does the primitive streak disappear? Ans- day 25
what is responsible for neural induction? where are these signals from? Ans- by BMP inhibitors from the pharyngeal endoderm, prechordal plate and notochord mesoderm
on what day does the neural plate consist of columnar cells that are taller than surrounding cells? Ans- day 20-21
during what week does the embryo fold into a 3D structure, most organs start to form, heart starts beating and neural tube forms? Ans- 4th week
- germ disc starts to look more like a body on what day does the neural tube close? Ans- day 28
anencephaly Ans- caused by failure of the anterior neuropore to close
- fatal
craniorachischisis Ans- failure of the entire neural tube to close
- fatal
spina bifida Ans- caused by failure of the posterior neuropore to close
- can be surgically fixed
what are the 3 major divisions of the ectoderm germ layer? Ans- 1. surface ectoderm (epidermis)
2. neural crest 3. neural plate/neural tube
T or F: all 3 major subdivisions of the ectoderm can form neurons Ans- true
what structures does the surface ectoderm form? Ans- - epidermis
- sensory epithelium
- lens/cornea
- etc
what structures does the neural crest form? Ans- - peripheral nervous system (PNS)
- melanocytes
- facial cartilage
- adrenal medulla
- Schwann cells
- glial cells
- sympathetic nervous system
- parasympathetic nervous system
what structures does neural plate/neural tube form? Ans- - brain
- spinal cord
- motor neurons
- retina
which ectoderm subdivisions have high BMPs? low? Ans- surface ectoderm has high BMP levels
neural plate/neural tube has low BMP levels, Sox TFs expressed
define neural plate Ans- portion of the ectoderm which will form the brain and spinal cord
define neurulation
1. primary
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