Basic concepts Flashcards
Forward genetics
random mutagenesis, screen for phenotypes; search for the mutation with the help of a visual marker. (different from reverse genetics = make mutation in gene of interest, then analyse phenotypes).
Patterning genes, different types in embryos: (3)
- Gap gene: loss results in a reduced number of segments.
- Pair-rule gene (even-skipped): loss allows only odd-numbered segments to develop.
- Segment polarity gene: loss leads to segments with similar head and tail ends.
The patterning genes allow the genes to become segmented.
syncytium
early in development the nuclei divide but the cells do not. This leads to a ‘bag of cytoplasm’ = syncytium. The syncytium allows for diffusion of proteins. At a certain moment the syncytium will cellularize; First the nuclei are in the centre → move to the periphery → syncytial blastoderm → cellular blastoderm with pole cells posterior
Gastrulation and segmentation
Gastrulation = major morphogenetic
process of development. Process where the ball of cells turns into an organism that has polarity and axes. Gastrulation can be defined as the main process in development. At the end of gastrulation there is obvious morphological segmentation. Patterning is important for this segmentation
Patterning
process of establishing positional information at the molecular level among similar cells. It helps cells respond differently depending on where they are. The cells look identical but start to differentiate in different ways
Body axes
- Dorsal-Ventral (D-V) (back-belly)
- Anterior-posterior (A-P) (nose-tail)
- Medial-lateral / left-right (L-R)
why is patterning not the same with differential gene expression?
because patterning is a process which establishes differential gene expression
what kind of genes set up the body axes?
maternal genes (Bicoid (anterior) inhibits caudal translation from maternal mRNA (both maternal). If you know the concentrations of bicoid and caudal, the ratio, you know their location within A-P axes within the embryo.)
what kind of genes responds to the activity of maternal gene proteins?
zygotic genes (Gap genes, pair-rule genes, segmentation genes, and selector genes)
Mesoderm give rise to:
Muscle (smooth and striated), bone, cartilage, connective tissue, adipose tissue, circulatory system, genito-urinary system, serous membranes, and notochord
Endoderm give rise to:
Stomach, colon, liver, pancreas, urinary
bladder, part of urethra, the epithelial
parts of trachea, lungs, part the pharynx,
the thyroid, the parathyroid, intestines
Ectoderm gives rise to:
-Surface epidermis: hair, nails, lens of the eye, sebaceous glands, cornea,
tooth enamel, anterior pituitary, the epithelium of the mouth and nose
-Neural crest: peripheral nervous system, adrenal medulla, melanocytes, facial cartilage, dentin of teeth
-Neural tube: brain, spinal cord, posterior pituitary, motor neurons, retina
whats the difference between fated, specified, and determined?
- Fate: lineage tracing, prediction based on position -> ‘we know what the cells (most likely) will give rise to – but the cells do not’
- Specified: ‘cells know what they will be, but can change their mind’
- Determined: ‘Cells know what they will be and will proceed no matter what’
Whole mount in situ hybridization (WISH)
- Cloning a gene of interest in vitro → produce RNA probe + providing labelled nucleotides. The labelled nucleotide (DIG labelling) can be followed through development. The RNA probe has to be complementary to the target RNA. The probe can anneal to the RNA of interest in the embryo.
- Embryo prep & probe hybridization: Fixation → protein digestion and post-fixation →prehybridization → hybridization → excess probe removal → detection of DIG molecule
