L25 Flashcards
How do we get information about the function of gene from its phenotype?
-Studying mutant organisms for particular gene, working out what gene does
-Make our own mutants and study
-Studying both types of mutants we can learn how particular mutations lead to phenotypic changes
Example of natural mutant (genetic change alters phenotype)
-6 fingers, extra digit, polydactyly
What can polydactyly tell us?
-normal role of gene is to prevent the extra digit
How many human genes have unkown function?
-4,000 (20,000)
What is a way we can find the function of mutant genes using other animals?
Find or create mutant genes in animals that we can learn their functions in humans
What is a genetic screen?
Increasing the rate of random mutation and select for a phenotype of interest, sequence the genome and identify the mutation
What is transgenisis?
Taking a gene of interest, copy and insert it into another organism (addition of foreign DNA)
what is CRISPR? simply
Deliberately break a particular gene and see what happens to organisms
examples of model organisms?
Mouse
zebrafish
drosophila
What are model organisms?
Easily raised in controlled environment and are easy to manipulate genetically
If DNA code is universal what does this mean?
Any DNA can be used by and organism even synthetic DNA
How does transgenesis work?
Adding gene of interest after regulatory sequence (controls production of protein)
What is CRISPR
Clustered regularly interspaced short palindromic repeats, an enzyme
Where did CRISPR evolve from?
in bacteria for antiviral defense
how does targeted mutation with CRISPR Cas9 occur?
-Decide which gene you wish to mutate
-design short ‘guide’ RNA that only binds to gene of interest
-join RNA guide and CRISPR cas 9 together
-Insert complex into organism cell (early embryo)
Once in the cell what does CRISPR cas9 do?
Finds target sequence in genome that matches guide RNA
Cas9 makes double stranded break in DNA at target site
Once break in DNA occurs what happens?
-Error in repair of DNA leading to small InDels at target site allowing the gene to be disrupted or mutated
-If repair template is provided, it may be used to edit DNA sequence
Can we fix genetic disease?
yes, if we know what causes the disease and have a method (gene therapy) to correct the defect
Somatic genetic disease fixing
-Target cells or organs affected
-Does not affect next generation (no change to germline)
How does gene therapy work in cystic fibrosis? (non integrated, somatic)
-Delivering DNA with functional copy of CFTR gene to lung cells via nebulizer
-Extra makes CFTR protein, restoring functions to some cells
(germline) what is pre implantation of genetic diagnosis?
-Testing of embryos for issues, and only implanting healthy embryos.
(germline) what are three parent babies?
-faulty gene is on mitochondrial DNA (mother) nuclear transfer to a donor egg can be used
