Genetics 2

physical characteristics, can be seen or measured, influenced by environment, genotype+enviroment=phenotype

: Genetic potential of an animal, inherited, the pair of alleles at the loci

inheritance of more than 2 full sets of chromosomes -uncommon in vertebrates

chromosome number is not an exact multiple of the haploid number -due to nondisjunction

only one chromosome from a pair is present in cells rather than the two copies usually found in diploid cells.

an extra chromosome

-Seperation of gene pairs is independent of other gene pairs -no pair of gene has influence on other genes

when 2 genes are found on the same chromosome they are considered to be linked

when 2 genes on the same chromosomes are split over due to crossing over during meiosis

Alleles will separate during meiosis so that only 1 allele is found in any gamete and chromosomal pairs must separate during gametogenesis (making of sperm/egg cells)

-Pattern of allele transfer from parent to offspring -dependent upon Mendel’s laws of inheritance

-another gene action -expression of one gene is dependent on the expression of another gene -ex. Labrador retrievers -2 genes: black gene B and extension of pigment gene E -E controls what is seen at B -B_E_-black lab -bbE_-chocolate lab -_ _ee- yellow lab

-some recessive alleles can lead to certain diseases/disorders/conditions -heterozygous individuals are carriers -only homozygous recessive inheritance allows the trait to be expressed -can cause economic damages to herd or flock -usually traced back to a popular sire that carried the recessive allele

Deleterious recessive trait -ovine hereditary chondroplasia -inheritance leads to incorrect bone and cartilage formation -do not live past 6 months -carriers undetected

Deleterious Recessive trait -fragile skin syndrome, blistering and slouching of skin

deleterious recessive trait -specifically in Hereford cattle -short-faced animals with difficulty breathing

Animal with homozyogus domiant genes is lethal and will not survive

Lethal Dominant Genes -homozygous recessive (tt)-long tails -heterozygous (Tt)-bobtails -homozygous dominant (TT)- LETHAL (not included in genotype ratio)

-homozygous recessive (dd)-normal stature -heterozygous (Dd)-chondrodysplasia dwarfism -homozygous dominant (DD)-LETHAL

-controlled by several genes -linked to desirable traits

-pigs can now produce PSE pork -pale, soft, exudative pork-watery and flavorless but very lean -undesirable pork -up to 40% of the market

porcine stress syndrome (PSS) -even small amounts of stress can lead to death -pigs can live to marketable age but death rates can be high during marketing -testable through halothane susceptibility test -semi lethal because they could make it to market but could die in travel

-reciprocal expression of the trait in males and females -ex. -horned dorset sheep -males P=horned, p=polled -females: P=polled, p=horned -in the heterozygous state, males are horned and females are polled

-both sexes carry the genes but only one sex will express it -ex. Milk production in females -cryptorchidism in males- only one testicle will descend