Inheritance Patterns Flashcards
single gene
what are genetic complexities beyound dominant and recessive?
Alleles have a dominance hierarchy that has to be determined if more than one allele is present (if 2 or more alleles are on the local)
What is MC1R ?
melanoreceptor gene - Ed is donimamnt black or ee which is a true red (only omozygous res will show red
where is the pigment diposited
the the root of hair or skin
what are the two different types of MC1R pigments
Phaeomelanin - producing red, yellow and cream
Eumelanin - producing black, brown and grey
when does black occur
in every heterozygous dominant pattern and recessive pattern
red only shows up in homozygous recessive
what is MC1R E+
wild type - the colour is influenced by other genes
What is the dominance hierarchy of alleles
ED>E+>e
what colours do they make
EDED- black
E+E+ - brown/wild type
ee - red
EDE+ black
EDe - black
E+e - brownish
what is codominant?
both phenotypes expressed together but observed seperately
what is incomplete dominance
both phenotypes are expressed as a blended appearnce
what are some autosomal recessive generalizations
- most are enzyme deficiencies (inborn errors of metabolism)
- phenotype is generally consistent
symptoms are severe (present at birth and often lethal)
consanguinity common (from ancestors)
what does autosomal recessive mean
recessive because neither parent actually looks infected
what are the exceptions for consistent phenotypes
von willebrand disease
cone-rod dystrophy
what are examples of carrier detection tests?
breedin tests(NEED TO KNOW DISEASE), direct tests(biochemical, DNA tets for the mutation) and indirect linkage tests for DNA
what is the breeding test
mate a sire of interest to either affected dams or heterozygous carrier dams and see if any affected offspring is born
if yes the sire is a carrier
what is the spider syndrome
severe skeletal abnormality
don’t survive very long
used to do the breeding test but now do the DNA testing
what is a direct biochemical test?
deficiency of betamannosidase in a homozygous recessive cause an affect gene dosage
what is direct DNA testing
most tests are PCR - whihc amplifies small amounts of DNA (HAIR ROOTS, BUCCAL SWAB, BLOOD, SEMEN)
what is indirect DNA linkage testing
used when causation gene isnt known yet
location of gene, or biochemical pathway is know
less accurate then direct tests - depends on distance of marker to gene
What is a marker?
its linked to the causative gene
DNA variation within an intron or other noncoding segment
markers do not affect any phenotype so have accumulated in animals
what is polycystic kidney disease
autosomal dominant
persian cats and breeds with persians
cysts developes by 12 months
renal failure later in life
premature stop codon in PKD1 gene
what is sex-linked?
gene on the sex chromosome
due to unequal sizes of chromosomes heterogametic sex has fewer genes
What is sex linked traits
effects the sexes differently
What are X-linked diseases
muscular dystrophy in dogs
factor VII hemophilia in horses and dogs
females have to be heterozygous to be effected, males just need X chromosome to be effected to be infected - males are effected young ans are unlikely to bred
what happend in hemophilia or horses?
males show their genotype, females to not
what are examples of X lnked traits
down silver gold colour in chicken sexing and fast slow primary feather growth in chickens
what is Y linked?
Holandric - transmitted only through males
gene for primary sex characteristics (sry)
penis and scrotum
genetic condition of dense hair in ears in men from india
what is sex influenced
more sex hormones can influence it - comb and wattle size in poultry
mahogany color of Ayrshire cattle
scurs
what are scurs
wiggle horns (not attached to the skull)
begin growing at 4 months in age
gene on chromosome 19 - not identified yet
bulls need only one copy to grow scurs - females need two copies
all scurred cattle P/p not P/P
all female scures are Sc/Sc - cull
what is epistasis?
genotype at one locus able to mask the phenotype cause by the genotype at another locus
ex. albinism masks colour of hair eyes hoof - all of which are controlled by different genes
