inheritance patters Flashcards by Robyn Schenk

homogametic

XX, ZZ

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heterogametic

XY, ZW (determines gender)

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how many alleles does an animals have/gene

two

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what is an allele

a version of a gene

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why is an example of an ethical mate choice for a dominant mutation in manx

-in manx cats to breed mm X Mm because you will result in 50% Mn (show quality) and 50% mm (tails)
-same precent will be show quality in Mm X Mm except 1/4 will be MM and die, with 1/4 long tail

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breeding Oo X Oo ovaro in horses

-1 oo (solid)
-2 Oo (ovaro)
- OO (white, lethal, intestinal issues)

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what happens if you breed Pp X Pp Chinese crested dog

1/4 lethal 1/2 show quality 1/4 powder puff

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dominance higharchy

-discovering which of more then two genes are more dominant
-because sometimes have more then 2 alleles at a locus

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melanocytes

produce pigment for hair follicle

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what are the two melanin pigments

phaeomelanin and eumelanin

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phaeomelanin

-melanin pigment
-red, yellow, cream

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eumelanin

-melanin pigment
-black, brown, grey

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melanocortin receptor 1 gene MC1R ED

ED=eumelanin=black

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melanocortin receptor 1 gene MC1R e

e/e=phaeomelanin=red

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melanocortin receptor 1 gene MC1R E+

-“wild type”
-colour depends on other genes
-i.e. brown

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heterozygote phenotypes

-heterozygots are different from either homozygotes
-codominant (both phenotypes expressed together but observed separately)
-incomplete dominant (both phenotypes expresses as a blend appearance

codominance in merle dogs

-MM= deaf, some microphthalmic (small eyes)
-Mm= merle, heterochromic irides, some black patches and some white
-mm= not merle

SLC45A2 or MATP gene in horses (codominance)

-CC=chestnut
-Cc=palomino
-cc=cremello
-if horses are e/e at MC1R, so no black (eumelanin) will be present

autosomal recessive generalizations

-most are enzyme deficiencies (inborn errors of metabolism)
-phenotype is generally consistent, exspecially within a family
-symptoms often severe
-consanguinity common (linebred)

why are many diseases called autosomal recessive

-because neither parents looks affected
-however not always autosomal recessive because you cant see it (can have reduced penetrance or be “dimmed”)
-but recessive X recessive=100% recessive offspring
-but such breeding is often not possible

symptoms for autosomal recessive (generlizations)

-often severe
-many such disorders are present at birth=congenital
-if untreated, they are often lethal

autosomal recessive (generlizations) consanguinity

-offten disorders show up when linebred is lised

implications of autosomal recessives

-cull the homozygote affected
-both parents are “obligate” carriers…cull?

what are the statistics if you were to breed two autosomal recessive carriers

-1 AA: 2 Aa: 1aa
-1/3 of unaffected not carriers
-2/3 of unaffected are carriers
-because 2/3 unaffected are carriers its important to have access to a carrier direction kit

carrier detection tests

-breeding test -direct tests (biochemical, DNA test for mutation) -indirect test (DNA linkage test)

carrier detection breeder tests

-mate a sire of interest to either affected dams of heterozygous carrier dams and see if any affected offspring are born -if so sire is a carrier

spider syndrome in sheep

-mate with carriers -Ss ewes (s/s do not survive to breeding age) -16 off spring all ok=99% chance sire is S/S -if S/s X S/s -1/4 of lambs will have spider syndrome

testing if a polled sire carries horns

-mate sire to horned cows (homozygous p/p) -polled in cattle is dominant to horned -7 offspring have no horns= 99% chance sire PP -(1/2)^7=0.0078

how many times do you have to breed test something matted to aa (recessive)

ho many times do you need to mate to Aa (carrier)

16x

mechanisms of a direct biochemical test

-measures specific range (level) of enzymes or protein -Beta-mannosidosis or deficency of beta mannosidase -homozygous normal=100% active (BB) -heterozygote=50% active (Bb) -affected=0% active (bb) -gene dosage=affect -not all samples give definitive results

mechanisms of direct test DNA test for the mutation

-most tests now based on PCR -method to amplify small amounts of DNA -samples: hair roots, buccal swab, blood, semen

indirect tests: DNA linkage test

-used when the causative gene is not known -location of gene, or biochemical pathway, etc. is known -less accurate then direct test i.e. depends on distance of marker to gene

DNA linkage test mechanism

-use a marker "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 -which allele segrates with the allele of interest is pedigree specific -therefore must sample the family ot test for carriers

when does recombination occur

during meiosis between homologous chromosomes

why would a carrier detection test be used for a dominant disorder

-if dominant dis order is late onset, so genotype is know prior to breeding