Mutations and Function of Individual Genes Flashcards
What are mutations?
Something that can be inherited or acquired
Permanent changes to the base sequence of DNA
What are germline mutations?
Mutations that re inherited and are passed on via the gametes
What are somatic mutations?
DNA is damaged or is copied incorrectly. Not passed onto next generation
What do mutations do?
Driving force for evolution
Can have a beneficial effect, no effect or a harmful effect
What is a dominant mutation?
One that causes a phenotype when heterozygous or homozygous dominant
What is a recessive mutation?
One that causes a phenotype only when homozygous recessive
What is a loss of function mutation?
A mutation might break a gene causing it to not work as well or not work at all
Often Recessive
Normal copy of the gene exists on the other chromosome which can replace the lost of function
What is a gain of function mutation?
Mutation causes a gene to work too well or do something unexpected
Often dominant
Have an allele that works too well so will not be replaced by normal copy
What is an autosomal recessive disease?
Example : cystic fibrosis
Typically not seen in every generation
Passed on by two asymptomatic carries
Males and females likely to inherit equally
What is an autosomal dominant disease?
Example : Huntingtons disease
Characteristics : occurs in every generation, affected individuals have an affected parent, males and females equally likely to inherit
What is an X-linked recessive disease?
Example : Haemophilia A or B
Characteristic : Offspring’s may be unaffected, female offspring may be carriers, affected males pass the allele to all daughters and no sons, affected females pass the allele to all sons
What are polygenic disorders?
Disorders that involve several genes acting together or environmental factors interacting with genes
e.g. diabetes, rheumatoid arthritis
How do we get information about the function of a gene from its phenotype?
By studying organism that are naturally mutant for a particular gene, we can work out what that gene might do
Where no natural mutants exist we can make our own
What are natural mutants?
Where genetic change alters the phenotype
How do we use genetic techniques to find out what a gene does?
Study organism that are naturally mutant for that gene
Increase rate of random mutation, select for trait of interest and sequence genome
Take gene of interest and insert into another organism and see what happens
What are model organisms?
Organisms that can be easily raised in a controlled environment and are easy to genetically manipulate
What is transgensis?
The process of transferring an exogenous DNA segment or gene to an animal so that it is able to pass the transgene on to offspring
How do we know if a gene variant is pathogenic?
We can damage or modify the gene we’re interested in by genetically modifying an organism or cell line
What is CRISPR?
Clustered regulatory interspaced short palindromic repeats
Cas9= associated protein 9
Envolved in bacteria for antiviral defence
Decide which gene you wish to mutate
Guide RNA will only bind to your gene of interest
How does Cas 9 work?
Enters nucleus and finds target sequence in genome that matches guide RNA
Makes double stranded break in DNA at target site
DNA repair enzymes with repair template which edits sequence at cut site
What is somatic genetic disease?
Targets the cells or organs affected
Does not affect the next generation
Gene therapy or gene editing
Example of gene therapy
Cystic fibrosis : one of the most common lethal single gene genetic conditions, defect in CFTR gene, which codes for chloride ion transfer
Delivering DNA with functional copy of CFTR restores some function to cells
Example of gene editing
CRISPR : Sickle cell disease - mutation in haemoglobin (oxygen carrying protein in red blood cells)
CRSIPR breaks bone marrow and red blood cells extracted, modified and returned
Can we fix genetic diseases?
Yes, but only if we know what causes it, have a way to correct the defect and have considered the ethics
