What is EPISTASIS?
interaction between 2 or more gene that controls ONE PHENOTYPE
What are the RATIO for recessive epistasis ususally?
9:4:3
Why is the ALBINO gene EPISTATIC to all other coat colours??
- Mutation in albino gene
- No tyrosiNASE produced
- TyronsinASE enzyme is responsible for converting tyrosin into precursor for melanin
What is the typical ratio of DOMINANT epistasis?
12;3:1
Remember the parental genotype of 9:7 ratio of puprple and white flowers
parents = PP ww x pp WW
ww recessive is epistatic to dominat, when ww, regardless of wethere the purple alle is present it will not be expressed
What are the two type of epigenetic tags and how do they affect genes?
DNA methylation
Histone modification
They can alter the chromatin structure within DNA, which will alter gene expression
What is MATERNAL imprinting?
- maternal allele is IMPRINTED hence silenced
therefore embryo will express paternal alleles
What is paternal imprinting?
- paternal allele is imprinted and silenced
maternal alleles are expressed in embryo
What type of imprinting does the IgF2 have and can you explain how it affects organism?
IgF2, is maternally imprinted, therefore maternal alleles are not expressed in the offspring even if functional
If father gene fort IgF2 is mutant it will have dwarfism effect on the offspring
What is the Prader-willi syndrome?
- paternal origin deleted
Due to the lack of maternally imprinted genes (polygenic)
What is Angelman syndrome?
- maternal origin is deleted due to lack of paternally imprinted genes
What is the genetic conflict hypothesis in relation to genomic imprinting?
- Paternal gene = promotes growth
- Maternal gene = suppresses growth
- Paternal related to promote growth as it may have multiple partners so wishes to promote growth of all of his offspring
- maternal supresses as it would prefer it to sort of equally distribute fitness
