Week Seven Notes ANEQ 328 Foundation in Animal Genetics
Week Seven Notes ANEQ 328 Foundation in Animal Genetics ANEQ328-001
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This 9 page Class Notes was uploaded by Destinee on Monday March 21, 2016. The Class Notes belongs to ANEQ328-001 at Colorado State University taught by Milton Thomas in Spring 2016. Since its upload, it has received 34 views. For similar materials see Foundation in Animal Genetics in Animal Science at Colorado State University.
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ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) Modes of Inheritance Foundational Information to Understand Inheritance o You need to know the genotype of parents. o How gene interact. o Mendel’s Principles o Genotype and allele frequency. Vocab Terms o Autosomal Chromosome Any other chromosome besides the sex chromosomes. o Sex Chromosome Chromosomes that determine the gender of a species, where female has two X chromosomes and a male has one X chromosome and one Y chromosome. o Locus The specific location of a gene on a chromosome. o Genotype One’s genetic makeup. Homozygous When the alleles are the same. Ex. BB or bb If an individual possess the genotype BB they are said to be homozygous dominant for that trait. If an individual possess the genotype bb they are said to be homozygous recessive for that trait. Heterozygous When the alleles are different. Ex. Bb If an individual has the genotype Bb they a said to be heterozygous for that trait. o Allele A variation of a gene. Bi-allelic When you are dealing with just two alleles. Ex. BB, Bb, and bb are bi-allelic for they each contain two alleles. Multi-Allelic When dealing with three or more alleles. Ex. AaBbCc Deleterious Allele A mutation within a gene that can harm the animal if passed down from parents to progeny. ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) Most deleterious alleles are homozygous recessive, meaning the offspring must acquire one recessive allele from each parent in order to have the condition. Nomenclature of Genotypes/Alleles in Modes of Inheritance o Letters Ex. BB and Dd o Abbreviations Ex. NNormal Ex. HYPP o Super and Subscripts O o O o Ex. X X or X /X o +/- o Descriptor (size) or a PCR Product Ex. AT AT AT 200 Base Pair Repeat AT AT AT AT201 Base Pair Repeat Can be summarized as 200/201 o Sequence (AGCT, SNP vs. indel vs. CNV) Autosomal Modes of Inheritance o No Dominance When an animal is heterozygous for a trait, but both are expressed half-way between the two homozygotes. Additive When each allele has an independent effect on a trait. Ex. Holstein Chromosome 14 G allele (alanine advantageous form effect = 100lbs for milk yield). If an animal has two GG alleles it will yield an extra 200lbs of milk. If an animal has the GC alleles it will yield only 100lbs of extra milk. If an animal has the CC alleles it will yield 0lbs of extra milk. o Complete Dominance When an animal is homozygous or heterozygous for a trait. Ex. Polled vs. Horned PPAn animal with these allele will have polled horns (no horns). PpAn animal with these alleles with have polled horns (no horns). ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) ppAn animal with these alleles will have horns. o Incomplete or Partial Dominance When an animal is heterozygous for a trait, but portrays the traits of the homozygous alleles. Ex. HYPP in horses. Impressive Syndrome miss-sense mutation. o Over Dominance When an animal is heterozygous for a trait, but has a heterozygous advantage and thus have a higher fitness than homozygous individuals. Ex. Callipyge in sheep. A mutation in sheep in that allows them to have more muscular buttocks. It is a heterozygous condition and the big C can only be inherited from the mother. o Co-Dominance When animal possess a heterozygote trait and both the dominant and recessive allele appear together in the animal’s phenotype. Ex. Roan Coat Color in Short Horn Cattle RRRed Coat RWRed and White Coat WWWhite Coat o Epistasis The interaction of genes at different loci. The expression of genes at one locus depends on the alleles on another locus. Ex. Coat Color In Labrador Retrievers A locus on chromosome 11 (Bb) controls the color of the coat. A locus on chromosome 5 (Ee) controls the extension of pigment. bbChocolate coat color BbBlack coat color E_B_ Black Coat E_bb Chocolate Coat ee__ Yellow Coat ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) Sex-Related Modes of Inheritance o Sex Linked When a specific trait is controlled on the loci of a sex chromosome (XY vs. XX). The X is inactivated in the male; although calico and male tortoiseshell cats are possible, they are rare and born sterile (meaning they can not breed). Ex. Coat Color in Cats O O X X Female With an Orange Coat X X Female Tortoiseshell Cat (Has Orange and Black Coat) o o X X Female With a Black Coat X YMale With an Orange Coat o Sex Limited When the phenotypic expression of a trait is limited to one sex (also known as sexual dimorphism). Ex. Beard growth Male Patterned baldness Milk Production (milk epd) Hen (h h ) vs. Cock (hh) for colored feathers. o Sex Influenced When the phenotypic expression of a trait is different between males and females (one allele may be dominant in the male and recessive in the female or vice versa.) Ex. Scurs in Cattle S Normal Dominant in Female S Scur Dominant in Males o Hemizygous Only having one pair of a gene. Ex. A gene on the X chromosome in a male. Exceptions to Clear Cut Mendelian Inheritance o Deleterious or lethal alleles o Incomplete or co-dominance o Silent or null alleles o Epistasis o Pleiotropy o Epigenetics o Variable expressivity Multiple variations in phenotype between the individuals with the same genotype. Ex. Piebald Spotting ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) S=Solid Color P S =Pie-bald spotting (large areas of white). 10 different possible phenotypes, 1 genotype. o Incomplete penetrance When individuals are carrying a variation of a gene (allele or genotype) that expresses an associated trait (phenotype). Ex. Huntington Disease and Neurodegenerative o G X E ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) Punnett Squares Vocab Review o Genotype One’s genetic make-up. o Phenotype One’s physical characteristics and trait measure. o Filial F1,2 ,3F , etc. the generations of the family and progeny. The first generation of a progeny is known as the1f generation. o Inter-Se Mate The process of random mating. o Repeated Back Crossing The crossing of a hybrid to one of its parents or someone that is genetically similar to the parent, in order to get offspring that are genetically similar to the parent. o Grading Up Cross breeding a breed with another breed. Upon breeding back 7/8 of your original breed, that animal is considered purebred. How To Draw A Punnett Square o Example 1: Cross a male with the alleles BB and a female with the alleles bb. Where BB equals a black coat and bb equals a red coat. b b B Bb Bb B Bb Bb Phenotypic Ratio: 100% Black Genotypic Ratio: 0 BB, 4Bb, 0bb (100% Heterozygous) o Example 2: Cross a heterozygous male (Bb) and a heterozygous female (Bb) from the previous generation. ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) B b B BB Bb b Bb bb Phenotypic Ratio: 3 Black: 1 Red (75% Black : 25% Red) Genotypic Ratio: 1 BB: 2Bb: 1bb (1:2:1) o Example 3: This Punnett square example is an example of Co-Dominance. Cross a female that has RW alleles and a male that has RW alleles. Where RR codes for a red coat, RW codes for a roan coat, and WW codes for a white coat. R W R RR RW W RW WW Phenotypic Ratio: 1 Red: 2 Roan: 1 White Genotypic Ratio: 1 RR: 2 RW: 1WW o Example 4: This Punnett square is an example of dealing with 2 different loci and different alleles. Cross a female with the following alleles BBPP and a male with the following alleles bbpp. Where the allele b represents coat color and the p allele represents the presence of horns. bp bp bp bp BP BbPp BbPp BbPp BbPp BP BbPp BbPp BbPp BbPp BP BbPp BbPp BbPp BbPp BP BbPp BbPp BbPp BbPp Phenotypic Ratio: 100% Black and 100% Polled Genotypic Ratio: 100% BbPp ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) o Example 5: Example of a dihybrid cross. Cross a male with the alleles BbPp and a female with the alleles BbPp from the previous generation. Where the allele b represents coat color and the p allele represents the presence of horns. (Remember PP and Pp mean polled and pp means horned). (This Punnett square is on pg. 45 in Bourdon textbook.) BP Bp bP bp BP BBPP BBPp BbPP BbPp Bp BBPp BBpp BbPp Bbpp bP BbPP BbPp bbPP bbPp bp BbPp Bbpp bbPp bbpp Phenotypic Ratio: 9 black and polled, 3 black and horned, 3 red and polled, 1 red and horned. o Example 6: Example of epistasis. Cross a female black lab with the alleles BBEE and a male yellow lab with the alleles bbee. BE BE BE BE be BbEe BbEe BbEe BbEe be BbEe BbEe BbEe BbEe be BbEe BbEe BbEe BbEe be BbEe BbEe BbEe BbEe Phenotypic Ratio: 100% Black Genotypic Ratio: 100% Heterozygous o Example 7: Example of a dihybrid cross and epistasis. Cross a male with the alleles BbEe and a female with the alleles BbEe from the previous generation. (This Punnett square is located on pg. 51 in the bourdon text.) ANEQ 328 Foundations In Animal Genetics Week Seven Notes (3/1/16-3/3/16) BE Be bE be BE BBEE BBEe BbEE BbEe Be BBEe BBee BbEe Bbee bE BbEE BbEe bbEE bbEe be BbEe Bbee bbEe bbee Phenotypic Ratio: 9 Black, 4 Yellow, 3 Chocolate