Genetics of development Flashcards
What are homeotic mutants?
one part of the body is transformed to another part
Why are drosophilia a good model?
Has striking mutants- looks way different in mutants, also low cost, east to breed, and has a fast life cycle
What is bithorax?
two sets of wings
What is antennapedia?
is legs instead of antennas
What is the bithorax and antennepedia mutations derived from?
one mutated gene
Within the thorax how many regions are there?
3
Within abdomen how many sections are there?
8
What is the anteriorposterior axis?
Is the head to bottom axis, is head versus rear
What is morphogen?
Molecule whose effects are concentration dependent, and establish the pattern of tissue development and body plan formation
How is gene expression diff in space and time?
some genes are turned on in only head, some are only turned on in adult stage versus juvenile stage
What do morphogen gradients determine?
Hox gene expression
What do hox genes do?
Control the identity of segments and appendages, also encode transcription factors
What is the genetic toolkit?
Is hox genes and genes that regulate them
are set of genes responsible for regulating animal developments, mostly encode cell signaling and transcription factors
What does it mean that hox genes are conserved across diverse species of animals?
they stay the same in their toolkit across alot of animals
Wat are the five classes of toolkit genes involved in regulating ap BODY AXIS?
Maternal effect genes
Gap genes
Pair rule genes
Segment-polarity genes
Hox genes
What are maternal effect genes?
They are the first class of toolkit genes that established the anterior and posterior end of the animal
Are expressed in the mother
Mutant phenotypes of maternal effect genes depend only on the genotype of mom
What two genes are maternal expressed genes? Where are they tethered?
Bicoid (anterior) and Nanos mRNA (posterior)
Upon fertilization what happens to the bicoid and nanos proteins?
They get expressed and form a gradient
What do Bicoid and nanos encode?
They encode transcription factors that regulate expression of the next set of genes
Say a female was homozygous recessive what happens to the egg, is it WT or mutant?
mutant
Say the female had genotype that was heterozygous, and the male was homozygous, are any offspring mutant?
NO! since mom is WT all offspring WT. Is a maternal effect gene
What genes are zygotically expressed?
Gap genes, pair rule genes, segment polarity genes, hox genes
Maternal effect genes have what role in the toolkit?
establishing interior and posterior (bicoid and nanos)
What are segmentation genes? What do they do?
Gap genes, pair rule genes, segment polarity genes, effect the number and organization of drosophila body segments
What do gap genes divide the embryo into?
broad regions
What does a mutated version of Kruppel do? What does this tell us?
It eliminates body segments in the anterior, is not viable, so gap genes lead to proper segmentation
What do pair rule genes affect?
Affect the development of pairs of segments
If you mutate pair rule gene hairy what happens?
The embryo misses every other segment, pair rule genes act in more narrow regions than gap genes
What segment polarity genes affect?
The organization of segments, mutations in this causes the mis organization within a particular segment.
What do gap genes do?
Define regional sections
What pair rule genes do?
Define individual segments
What do segment polarity genes do?
define organization of individual segments
The order of hox genes in the chromosome responds to what?
The the order of body regions that are affected by each Hox gene.
Where are hox genes expressed? What do they give rise to?
Expressed in restricted regions in the embryo, give rise to the corresponding adult body part
How do HOX genes control the identity of segments and appendages?
They are transcription factors so they regulate expression of networks of other genes
Are hox genes sequence specific DNA binding proteins?
Yes
What do HOX genes bind to in the sequence?
cis acting regulatory sequences of other genes to activate and repress them
Are all genes in the toolkit transcription factors?
yes
What is hunchback?
is a promoter which bicoid binds to to to express the gap gene
IS the hunchback expression and bicoid protein both have gradients?
yes
How many sites does bicoid bind to to activate expression of hunchback?
has to be three sites
What concentration of bicoid do we need to have hunchback work?
high levels, need a threshold level to do it
What is eve?
A pair rule gene, cis acting regulatory elements control expression of it by binding to transcription factors
