molecular patterns 2 Flashcards
when do the cells that would become the fetus commit and what are they called?
inner cell mass cells that are isolated in the blastocyst. the ICM are called embryonic stem cells
if deleting a gene is called a knockout, what is a knock in?
when you introduce new genes into the genome. or by replaceing a wild type gene with a specific mutation
what is a homeotic mutation?
mutation where one structure is replaced with another or duplicated
what does duplications from homeotic genes tell us?
the genes that were mutated are essential in forming that body part
what is a homeobox?
DNA sequence responsible for different homeotic mutations. typically 180 bp in leangth. they are transcription factors that bind to promoters which are AT rich motifs
homeobox transcriotion factors have a segment of the TF protein that binds to DNA. what is that segment called?
homeodomain is the segment of the homeobox transcription factors that bind to DNA
homeotic mutations are due to mutations in
homeobox transcriotion factors
The part of the homeobox transcription factor (protein) that does the actul binding to DNA is called and made of
the homeodomain. it is made 3 alpha helices and it is helix 3 that actually makes contact with the DNA
where do homeobox genes bind? what determines the specificty of the homeodomain?
TAAT rich DNA sequences. homeodomains are not very specific. the protein complex that is formed from the homeodomain transcription factors is what determines the specificity.
which of the homeobox genes bind to the DNA
only the homeodomain binds to the DNA
what is the function of a Hox gene? and what is their function?
they are expressed in a particular embryonic domain and their job is to develop the particular body part that correlates to that domain
what is the relationship between the location of a Hox gene on a DNA vs. its control of a body part?
the Hox genes are arranged from 3’ to 5’ from forward to back. so the gene closest to 3’ end is in charge of anterior feature and 5’ end makes the dorsal features
what is the difference btween Hox genes in flies vs mice and humans?
flies have only 1 cluster of Hox genes, humans have 4
what is the difference between orthologs and paralogs?
orthologs are homologous genes between two species
paralogs are homologous genes within the same species/animal
contrast spatial and temporal co-linearity
spatial co-linearity means the genes closer to the 3’ end start closer to the head and each subsequent one back starts closer to the tail.
Temporal co-linearity describes the fact that the 3’ end genes are expressed earlier than the 5’ end genes
what is a sign that Hox genes have redundancies?
single mutants in Hox genes have less severe phenotypes than double or tripple mutations
what kind of mutation leads to anterio transformation vs. posterior transformation?
Loss of function mutation- anterior transformation-posterior parts look like anterior parts
gain of function mutation- posteior transformation- anterior parts look likeposterior parts
if there are no Hox genes in the head, what makes the head?
in drosophala they have Otd genes. mouse have Otx1 and Otx2
where does Otd sit in the transcriptional cascade?
Otd sits upstream of the transcriptional cascade. it is a homeobox gene but not part of the hox clusters.if you delete it, drosophala has no head
what is the consequence of knowing the transcriptional code of the inner cell mass??
you can use induce pluropotent stem cells to cure disease
