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 the transmission of genetic or physical traits from parent to offspring.

Gregor Mendel Austrian Monk Considered the “Father of Heredity” He conducted plant breeding experiments in their monastery garden. In 1865 he made his work public, units of inheritance.

What makes us unique? Each of the 100 Trillion cells in our body except the red blood cells contains the entire human genome, in the nucleus of every cell is the genetic information “blueprint” to construct the individual. 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 like segments called chromosomes Chromosomes occurs in pairs in every cell of our body except in the sperm and ovum. Chromosomes numbers are the same for each species.

Chromosome Numbers Species Diploid # Haploid # Cattle 60 30 Swine 38 19 Sheep 54 27 Horse 64 32 Human 46 23 Chicken 78 39 Goat 60 30 Donkey 62 31

Sex Determination Females contribute an X chromosome towards the sex of their offspring. Males can contribute an X or a Y chromosome toward the sex of their offspring. Absence of an Y chromosome results in a the embryo developing into a female. Presence of an Y chromosome results in the embryo developing into a male.

Tell me what I am ?????

Genes Chromosomes contains several units of inheritance “genes”. Genes usually occurs in pairs, one from each parent. Some traits are inherited directly from one set of genes. Some traits are inherited through several sets of genes.

Terms to know (you need all this) Homozygous – contains 2 identical genes for the same trait (ie. AA, BB, cc) Heterozygous – contains 2 different genes for the same trait (ie. Aa, bB, Cc) Phenotype – Outward appearance of a trait, coat color, 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 of the gene. AB Determine the possible gametes of AaBB AB aB

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 and dominant gene. It has the power to overshadow the recessive gene when 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 the absence 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 recessive cows. 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 whiskers has 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 have short whiskers from the cross of two long-whiskered seals, one that is homozygous dominant and one that is heterozygous? If one parent seal is pure long-whiskered and the other is short-whiskered, what percent of offspring would have short whiskers?

Practice Problem #1

Practice Problem #2 In purple people eaters, one-horn is dominant and no horns is recessive. Draw a Punnet Square showing the cross of a purple people eater that is hybrid for horns with a purple people eater that does not have horns. Summarize the genotypes & phenotypes of the possible offspring.

Practice Problem #2

Practice Problem #3 Mendel found that crossing wrinkle-seeded plants with pure round-seeded plants produced only round-seeded plants.  What genotypic & phenotypic ratios can be expected from a cross of a wrinkle-seeded plant & a plant heterozygous for this trait (seed appearance)?

Practice Problem #3

Your Turn!!!

What are Sex Linked Genes? Some recessive genes are attached to the X and Y chromosomes Humans: Colorblindness and Baldness are on the X chromosomes 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 is expected genetically Horned calf from polled parents Loss of some or extra body parts Lethal Mutation: causes death at birth Sublethal Mutation: limits animals ability to grow to maturity Beneficial Mutation: loss of tail in lambs

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 related animals Linebreeding: mating distantly related animals Outcrossing: mating unrelated animals in the same breed. Crossbreeding: mating animals of same 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 200 bu/acre Vigor only expressed in crossbreeding