Embryo Pattern Formation II Flashcards
How do you make knockouts?
Delete any gene via ES stem cells
How do you make knockins?
Replace one version of a gene with another via ES cells
How are transgenics made?
Injection of DNA into pro-nuclei of fertilized eggs of mice. The DNA integrates randomly into genome of offspring.
A homeotic mutation is one where a structure is ____ with another or ____.
A homeotic mutation is one where a structure is REPLACED with another or DUPLICATED.
Homeobox is a DNA _____ that is ~___bp in length and encodes a protein domain called a _____. They encode ____ that typically initiate a ____ of _____ necessary for development of a body structure or cell type.
- ____ bind __-rich sequences found at ____ and ____
- they consist of 3 ___ ___ with AAs in ___#3 that make contact with ____.
-In order to confer specificity, ____ must form ____.
Homeobox is a DNA SEQUENCE that is ~180bp in length and encodes a protein domain called a HOMEODOMAIN. They encode TFs that typically initiate a CASCADE of GENE EXPRESSION necessary for development of a body structure or cell type.
- HOMEODOMAINS bind AT-rich sequences found at PROMOTERS and ENHANCERS
- they consist of 3 ALPHA HELICES with AAs in HELIX#3 that make contact with DNA.
-In order to confer specificity, HOMEODOMAINS must form COMPLEXES.
Hox genes function in ______.
- the 5’ most HOX genes are most ___ body parts, expressed at ___ end of embryo.
- the 3’ most genes are ____, expressed at the __ end of embryo.
Common theme in evolution: ____ and ____ in number.
Hox genes function in PATTERNING THE BODY AXIS.
- the 5’ most HOX genes are most POSTERIOR body parts, expressed at 3’ end of embryo.
- the 3’ most genes are ANTERIOR, expressed at the 5’ end of embryo.
Common theme in evolution: CONSERVATION and EXPANSION in number.
Segments of somites:
_____ make vertebral skeleton
_____ make skeletal muscles
_____ makes dermis
Segments of somites:
SCLEROTOME make vertebral skeleton
MYOTOME make skeletal muscles
DERMATOME makes dermis
Genes further 3’ have more ____ expression boundaries, which is called ____ _____.
3’ Hox genes are also expressed earlier in development than 5’ genes which is called ____ _____.
In short, gastrulation goes from ____—->____
Genes further 3’ have more ANTERIOR expression boundaries, which is called SPATIAL CO-LINEARITY.
3’ Hox genes are also expressed earlier in development than 5’ genes which is called TEMPORAL CO-LINEARITY.
In short, gastrulation goes from ANTERIOR—->POSTERIOR
Hox code: different groups of cells express ___ ____ of hox genes depending on their position along the ________.
Hox code: different groups of cells express DISTINCT PATTERNS of hox genes depending on their position along the A-P AXIS.
Orthologs Vs Paralogs
Orthologs are homologous genes between species
Paralogs are homologous genes within a species.
Loss of function/ Hox KOs leads to ______ transformations; example: deletion of Hoxa3 or d3 results in generation of vertebral bones that have more ____ morphology.
Single mutants in Hox genes have ___ severe phenotypes than ___/___ mutants, an example of ____.
Gain of function mutations lead to ____ transformations.
Loss of function/ Hox KOs leads to ANTERIOR transformations; example: deletion of Hoxa3 or d3 results in generation of vertebral bones that have more ANTERIOR morphology.
Single mutants in Hox genes have LESS severe phenotypes than 2X/3X mutants, an example of REDUNDANCY.
Gain of function mutations lead to POSTERIOR transformations.
Formation of head structures is controlled by ____ orthologs called ___ and ___.
Formation of head structures is controlled by OTD orthologs called OTX1 and OTX2.
Difference between Otx1/Otx2. What kind of proteins are they?
Transcription factors!!
Otx1 -/- mutants survive embryogenesis but brain structures including cortex are smaller.
Otx2 -/- mutants die early in embryogenesis. It deletes the forebrain precursors in CNS. These mutants resemble Otd mutants.
When Otx or Otd are deleted, the downstream genes are NOT turned on.
-Otd or Otx misexpression leads to ectopic expression of neural structures because they are sufficient to turn on downstream genes in non-neural tissue.
Otx and Otd are functionally redundant/functionally equivalent.
TFs that are sufficient to make iPS cells
OCT4, SOX2, NANOG, C-MYC, KLF4
____ mutations in HOXD13 lead to _____.
The mutation is specifically in _____, _____, which affects _____
MISSENSE mutations in HOXD13 lead to SYNPOLYDACTYLY.
The mutation is specifically in 3RD ALPHA HELIX OF HOMEODOMAIN, which affects DNA BINDING
