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Are your Earlobes attached or detached? Is this genetic or environmental? Which brand of vehicle do you prefer? Is this genetic or environmental? Which type of hairline do you have, straight or widows peak? Is this genetic or environmental? What is your favorite food? Is this genetic or environmental? Do you have hair above your knuckles? Is this genetic or environmental? What is your favorite TV show? Is this genetic or environmental? Can you roll your tongue? Is this genetic or environmental? Do you have a hitchhikers thumb? Is this genetic or environmental? What is your favorite drink? Is this genetic or environmental? Are you a morning person or a night owl? Is this genetic or environmental? Animal Science Genetics in History Gregory Mendel Priest from a monastery in Europe. Mendel was first to succeed at predicting how traits are passed on Genetics in History Traits: characteristics that are inherited. Heredity: the passing of traits from parent to offspring Genetics : the study of heredity and traits The Law of Segregation The Law of Segregation: Every individual has two alleles of each gene. After meiosis, Sperm cells have one allele for a trait Ovum cells have one allele for a trait. When combined at fertilization you have two alleles for each trait. Law of Independent Assortment Mendel concluded that different traits are inherited independently of each other, so that there is no relation, for example, between a cat's color and tail length. Genetics in History Garden peas reproduce sexually Male sex cells – sperm cells Female sex cells – ovum cells Genetics in History Mendel selected garden peas because: They can self pollinate He could control their traits. Genetics in History P1 Generation The original parent or the true breeding plant. Genetics in History F1 Generation The offspring of the parent (P1) Genetics in History F2 Generation The offspring of the (F1) generation. Genetics in History Compare this to your family P1 generation – Your grand parents F1 generation – Your parents F2 generation – You Genetics in History First Generation (P1) Mendel cross pollinated tall pea plants with short pea plants. Mendel found that All the pea plants grew to be tall The short trait had disappeared Hybrid: offspring of the parents that have different forms of the trait Genetics in History Second Generation (F1) He allowed the first generation to selfpollinate. Planted the seeds from the self- pollination. Genetics in History Discovered that: ¾ were as tall as the parent plants. Dominant Genetics in History ¼ were short like the parent generation. Recessive They occurred in a ratio of 3:1 The short trait reappeared. Genetics in History Why did the Short Trait reappear? Because of the Rule of Dominance! The Rule of Dominance Dominant traits: The trait that shows up ¾ of the time. Shown with uppercase letters. TT The Rule of Dominance Recessive traits: The trait that shows up ¼ of the time. Shown with lowercase letters tt The Rule of Dominance When identifying these traits we always use the letter of the dominant trait! Examples: Polled = P Black =B Tall=T Horned =h White =b Short=t Genetics Homozygous: Genes that possess two dominant alleles or two recessive. TT or tt Genetics Heterozygous: Genes that possess one dominant and one recessive trait. Tt Genetics Genotype: The genetic composition of an individual Example: TT Hh ww Genetics Phenotype: How the trait is expressed. Example: Tall Horned Red/Black Genetics Example: Two black calves might have the same phenotype, but different genotypes. One may be Heterozygous, (Bb) One may be Homozygous, (BB) The Punnet Square Mendel's pea plants T Tall = TT P1 Generation t T t T t t T t T t Short = tt F1 Generation T The Punnet Square Mendel's pea plants T Tall = Tt F1 Generation T TT T t t T t tt Tall = Tt F2 Generation t Incomplete Dominance What Happens when? Incomplete Dominance Incomplete Dominance When traits are inherited incompletely, or they mix. Red Shorthorn Cattle Genotype (RR) White Shorthorn Cattle Genotype (R’R’) Incomplete Dominance When they reproduce the offspring are both red and white in color. New phenotype occurs because the trait that controls pigment is affected. Incomplete Dominance R’ R’ R R’R R’R R’R R’R R Incomplete Dominance R’ R R’ R’R’ R’R R’R RR R Codominance The expression of both alleles Neither one of the alleles are dominant or recessive, and is expressed in the offspring. Ex. - In some flowers, alleles for petal color are codominant. Codominance Alleles are written with superscripts. Genotype = PR PR Phenotype = Red Genotype = Pw Pw Phenotype = White Codominance PR PR Pw PRPW PRPW PRPW PRPW Pw Law of Independent Assortment Mendel concluded that different traits are inherited independently of each other, so that there is no relation, for example, between a cat's color and tail length. This is actually only true for genes that are not linked to each other. Gender The sex of an animal is determined by the sex chromosomes. There are two types, X shaped chromosomes Y shaped chromosomes Vertebrate males have a XY Vertebrate females have a XX Sex-linked Genes Fruit Flies (Drosophila melanogaster) inherit sex chromosomes the same as humans. Traits located on the sex chromosomes are called sexlinked traits. All sex-linked traits are located on the X chromosomes. Sex-linked Genes Male Fruit Flies Phenotype = White Eyes Genotype = Xr Y Female Fruit Flies Phenotype = White Eyes Genotype = Xr Xr Sex-linked Genes Xr Y XR XRXr XRY XR XRXr XRY Sex-linked Genes XR Y XR XRXR XRY Xr XRXr Xr Y Meiosis Cell division where one body cell produces four gametes, containing half the genetic material of the parent cell. Gamete: a cell which fuses with another during fertilization. Meiosis There are only two cells that have undergone Meiosis. Sperm Cells Egg Cells Meiosis Sperm Cells Male reproductive cells Spermatogenesis Meiosis Egg Cells Female Reproductive Cells Oogenesis Meiosis Meiosis divided into two sections with a total of eight phases. Meiosis 1 Meiosis II These phases are continuous and flow one right after the other. Meiosis I Prophase 1 Chromosomes Coil Up Chromosomes Line up in Tetrads Tetrad consists of two homologous made up two sister chromatids. Crossing over occurs Meiosis I Metaphase 1 Centromere becomes attached by spindle fibers Tetrads line up along the equator Meiosis I Anaphase 1 Chromosomes move to opposite ends of the cell. Polar Ends Meiosis I Telophase 1 Spindle fiber breaks down Chromosomes uncoil Meiosis II Prophase II Metaphase II Anaphase II Telophase II The above steps are exactly the same as mitosis. Mitosis Prophase Metaphase Anaphase Telophase Meiosis The end product of meiosis is four cells which are genetically different then the parent cell, with half the genetic information. Meiosis ½ the information comes from the male sex cell ½ the information comes from the female sex cells When the two cells (gametes) combine all the necessary genetic material is there. Meiosis Fertilization The fusion of gametes to produce a new organism. Meiosis Once the sperm and ovum have joined the fertilized egg is called a zygote Environmental Influences The genetic make-up of an organism only determines the potential of an organism. Environmental Influences External Influences Temperature Light Nutrition Environmental Influences Internal Influences Internal body functions Hormones (ralgro, synovex) Age Environment vs. Heredity An organism's traits and performance are a sum total of its ENVIRONMENT acting upon its GENETIC information. Environment vs. Heredity Some TRAITS are influenced more by an organism's ENVIRONMENT than by its GENETICS, while others are influenced more by genetics. Heritability The percentage that a trait is affected by its genetic information is called HERITABILITY. A heritability factor of 0.0 means that a trait is influenced very little by genetic information A heritability factor of 1.0 means that a trait is influenced very little by the environment. Examples of Heritability Birth Weight = .40 Weaning Weight = .30 Multiple Births = 0.0 - 0.10 Dressing Percentage = .60 Breeding Systems Breeding Systems Purebred=a recognized strain established by breeding individuals of unmixed lineage over many generations. Breeding Systems Crossbreeding=A crossbreed refers to an animal with purebred parents of two different breeds. Breeding Systems Hybrid Vigor= Increased vigor or other qualities from the crossbreeding of genetically different animals. Breeding Systems • Average birth weight for the Black Baldie calves was 72 lb. — 3 lb. heavier than the purebred sires, but extremely desirable and nearly ideal for commercial operations. • At weaning the Black Baldie calves were 11.9 lb. heavier than the purebred calves, • While both breed groups were similar for fat thickness (Angus = 0.52 vs. Hereford = 0.54), Black Baldie steers had about 13 more lb. of carcass weight and about ¾ of an inch more rib-eye area. • While feed conversion was nearly identical, Black Baldie steers outgained the purebred steers by almost .15 of a lb. per day. • Heifer calves were bred and part of the group was marketed through the Circle A Production Sale with the baldie average price $110 more than the straight black heifers. Breeding Systems Linebreeding=This is the breeding of animals that share common ancestors but are not closely related. For example the animals may share a common greatgrandparent. Inbreeding=This is the breeding of closely related animals. Brother-Sister, Parent-Offspring, ½ brother - ½ Sister Performance Pedigrees summarizes a particular animal's own performance records as well as records of ancestors, siblings, and progeny. Progeny = offspring EPD EXPECTED PROGENY DIFFERENCE an INDICATION of the amount of GENETIC merit that an animal will pass on to its offspring. EPD example a bull with an EPD for weaning weight of +25.0 pounds means that the bull's offspring should average 25.0 pounds more at 205 days of age than offspring of a bull with an EPD for weaning weight of 0.0 pounds. EPD Abbreviations BW = Birth Weight WW = Weaning Weight (205 days of age) YW = Yearling Weight (365 days of age) milk = maternal milking ability expressed in pounds of calf weaned. Adaptability The ability of a BREED to become SUITABLE to specific environmental conditions Type a group of ANIMALS that are grouped together according to the PRODUCTS they produce Examples -- Beef type cattle, Dairy type cattle, Wool type sheep, Mutton type sheep Species a group of ORGANISMS that have several common CHARACTERISTICS that differentiate them from others. Breed animals having a common ORIGIN and CHARACTERISTICS that distinguish them from other groups within the same SPECIES.