Intro to Agriculture AAEC Paradise Valley Spring 2015
Animal Genetics Intro to Agriculture AAEC Paradise Valley Spring 2015 Genetics: the science of heredity.
Heredity is thetransmission of geneticor physical traits fromparent to offspring. Gregor Mendel Austrian Monk Considered the Father of Heredity
He conducted plant breedingexperiments in their monasterygarden. In 1865 he made his workpublic, units of inheritance. What makes us unique? Each of the 100 Trillion cells in our body exceptthe red blood cells contains the entire humangenome, in the nucleus of every cell is the geneticinformation blueprint to construct theindividual. It is the Deoxyribonucleic acid (DNA) Function of DNA Genetic code for almost every organism. Provide template for protein synthesis. DNA in Pop Culture Chromosomes The DNA in every cell is located in rod likesegments called chromosomes Chromosomes occurs in pairs in every cell ofour body except in the sperm and ovum. Chromosomes numbers are the same for eachspecies. Chromosome Numbers Species Diploid # Haploid # Cattle Swine Sheep Horse Human Chicken Goat Donkey 62 31 Sex Determination Females contribute an X chromosome towards thesex of their offspring. Males can contribute an X or a Y chromosometoward the sex of their offspring. Absence of an Y chromosome results in a theembryo developing into a female. Presence of an Y chromosome results in theembryo developing into a male. Tell me what I am ????? Genes Chromosomes contains several units of inheritance genes.
Genes usually occurs in pairs, one from eachparent. Some traits are inherited directly from oneset of genes. Some traits are inherited through several setsof genes. Terms to know (you need all this)
Homozygous contains 2 identical genes for thesame trait (ie. AA, BB, cc) Heterozygous contains 2 different genes for thesame trait (ie. Aa, bB, Cc) Phenotype Outward appearance of a trait, coatcolor, polled, horned. Genotype Genetic classification of a gene,AA,Aa, aa. Allele- Location of a gene on the chromosome. Genotype or Gamete Genotype contains two copies of the gene.
AaBB Gamete (sex cells) contains only one copy ofthe gene. AB Determine the possible gametes of AaBB ABaB Gamete or Genotype State if its a gamete or genotype. Aa D Genotype
DdEeFFgg sRtxyq AaBBeeFF adgEFT Genotype Gamete Genotype Gamete Genotype Gamete List all the possible gametes.
From the genotype AaBb AB Ab aB ab What are dominant genes?
Write all this What are dominant genes? The gene that express itself, the powerful anddominant gene. It has the power to overshadow the recessive genewhen there is complete dominance. Some examples are: White faced in cattle Droopy ears in swine Polled in cattle Black coat color in Angus cattle What are Recessive Genes?
Write all this What are Recessive Genes? The gene that is overshadowed by a dominant gene Recessive genes can only express themselves in theabsence of the dominant gene Polled vs Horned (Pp) (pp) Black wool vs white (Ww) (ww) Dwarfism vs normal size (dd) Albino Punnet Square Angus - Black coat color is dominant.
BB = Homozygous Dominant and Black Bb = Heterozygous and is black bb= Homozygous recessive and red A heterozygous bull is mated to 50 homozygous recessivecows. How many calves are black? How many calves are red? What is the genotypic and phenotypic ratios? Punnet Square Results 2 Heterozygous = Bb 2 Homozygous Recessive = bb
25 Black, 25 Red Genotypic ratio = 0:2:2 Phenotypic ratio = 2 Black: 2 Red Practice Problem #1 Let's say that in seals, the gene for the length of the whiskershas two alleles. The dominant allele (W) codes long whiskers& the recessive allele (w) codes for short whiskers. What percentage of offspring would be expected to haveshort whiskers from the cross of two long-whiskeredseals, one that is homozygous dominant and one that isheterozygous? If one parent seal is pure long-whiskered and the other isshort-whiskered, what percent of offspring would haveshort whiskers? Practice Problem #1 Practice Problem #2 In purple people eaters, one-horn is dominant and no hornsis recessive. Draw a Punnet Square showing the cross of apurple people eater that is hybrid for horns with a purplepeople eater that does not have horns. Summarize thegenotypes & phenotypes of the possible offspring. Practice Problem #2 Practice Problem #3 Mendel found that crossing wrinkle-seeded plants with pureround-seeded plants produced only round-seededplants. What genotypic & phenotypic ratios can beexpected from a cross of a wrinkle-seeded plant & a plantheterozygous for this trait (seed appearance)? Practice Problem #3 Your Turn!!! What are Sex Linked Genes?
Some recessive genes are attached to the X and Ychromosomes Humans: Colorblindness and Baldness are on the Xchromosomes In Men, traits expressed anytime present In Women, must have two recessives to show trait Children get baldness from mothers If Dad is bald, will you be bald? Baldness is carried by the mother What if Mom is bald? What is Incomplete Dominance?
If both genes express themselves Shorthorn Cattle: Red male mated to a White female = Roan calf RR crossed rr = Rr Punnet Square Shorthorn Cattle
RR = Red rr = white Rr = roan If a red bull (RR) is mated to a white cow(rr), what color will the calves be? Shorthorn: Red X White Punnet Square If a red bull (RR) is mated to a roan(Rr) cow, what color will the calves be? Shorthorn: Red X Roan What if Both Parents are Roan? What is a Mutation? Dramatically different from what isexpected genetically Horned calf from polled parents Loss of some or extra body parts Lethal Mutation: causes death at birth Sublethal Mutation: limits animalsability to grow to maturity Beneficial Mutation: loss of tail inlambs What is Heritability? Chance that traits will be inherited
Low: multiple births, fat covering Medium: birth weight wean weight, milk, wool grade, carcass weight, rate of gain High: Loin eye area, fleece length & quality Mating Systems Upgrading: mating purebreds with grade animals
Inbreeding: mating closely relatedanimals Linebreeding: mating distantlyrelated animals Outcrossing: mating unrelatedanimals in the same breed. Crossbreeding: mating animals ofsame species but different breeds. What is Hybrid Vigor? Offspring will outperform either of the parents
Example: Corn Breed A yields 100 bu/acre Corn Breed B yields 100 bu/acre Crossbreed A & B yields corn that yields bu/acre Vigor only expressed in crossbreeding