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Genetics - PowerPoint PPT Presentation

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Genetics By Mr. Gerbitz What is Selection ? Mating animals to produce certain characteristics Low Birth weight Heavier Weaning Weight Color Horned or Polled Temperment What makes an animal they way that they are?

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Genetics l.jpg



Mr. Gerbitz

What is selection l.jpg
What is Selection?

  • Mating animals to produce certain characteristics

  • Low Birth weight

  • Heavier Weaning Weight

  • Color

  • Horned or Polled

  • Temperment

What makes an animal they way that they are l.jpg
What makes an animal they way that they are?

  • Animals are the result of Feed, Health, and Inheritance (genetic material)

  • Feed is fastest to correct

  • Genetics last longest

What is genetics l.jpg
What is Genetics?

  • All body cells contain “Blueprints” with instructions as to how an animal will look or act etc.

  • One Gene comes from each parent (pairs)

  • Genes are divided into sections (Chromosomes) that carry genes

  • Sex chromosomes: male = XY, female = XX

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What are Dominant Genes?

  • Dominant Genes = one gene overshadows the other

  • Angus Cattle: black is dominant, red is not (Bb)

  • Hereford: white face is dominant (Ww)

  • Hampshire Hog: white belt is dominant

  • Horns are dominant (Pp)

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What are Recessive Genes?

  • The gene that is overshadowed by a dominant gene

  • Recessive genes can only express themselves if both genes are recessive

  • Polled vs Horned (Pp) (pp)

  • Black wool vs white (Ww) (ww)

  • Dwarfism vs normal size (dd)

  • Albino

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Punnet Square

  • P = horned

  • p = polled

  • If a homozygous horned cow (PP) is mated to a homozygous polled bull (pp), what percent of the calves will be horned, polled?

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Punnet Square

  • If a homozygous horned cow (PP) is mated to a heterozygous horned bull (Pp), what percent of the calves will be polled?

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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

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What is Incomplete Dominance?

  • If both genes express themselves

  • Shorthorn Cattle: Red male mated to a White female = Roan calf

  • RR + WW = RW

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Punnet Square

  • Shorthorn Cattle

  • R = Red

  • W = white

  • RW = roan

  • If a red bull (RR) is mated to a white cow (WW), what color will the calves be?

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Punnet Square

  • If a red bull (RR) is mated to a roan (RW) cow, what color will the calves be?

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Undesirable Characteristics

  • Dwarfism

  • Monorchid = only one testicle descends

  • Cryptorchid = no testicles descend

  • Short ears & tails

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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

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What is an Abnormality?

  • Similar to a Mutation, only it is caused by something in the environment

  • Siamese twins

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What is Heritability?

  • Chance that traits will be inherited

  • Low: multiple births, fat covering

  • Medium: birth wt, wean wt, milk, wool grade, carcass wt, rate of gain

  • High: Loin eye area, fleece length & quality

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  • Currently have ewes that wean 70 lb lambs

  • Want to raise weaning wt to 110 lbs

  • Select a ram with a wean wt of 110 lbs

  • Heritability of weaning wt is 30%

  • What can you expect new lamb crop to weigh at weaning?

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  • What is the difference in current weaning wt and that of the new ram?

    110 - 70 = 40 lbs

  • Heritability % x difference

    30% x 40 = 12 lbs

  • Can expect a gain in weaning wt of 12 lbs

  • 70 lbs + 12 lbs = 82 lbs

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Mating Systems

  • Random Mating: all males have an equal opportunity to mate with all females

  • Outcrossing: mating purebreds with unrelated purebreds

  • Inbreeding: mating related animals

    • Linebreeding: parents mated to offspring

  • Crossbreeding: mating animals of same species but different breeds

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What is Hybrid Vigor?

  • Offspring will outperform either of the parents

  • 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

  • Donkey mated to a horse = Mule

    • mule is sterile

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What are Exotics?

  • Animals not common to United States

  • Difficult to define today

  • New breeds are exotics

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Genetic Terms

  • Genotype: genetic makeup (Bb)

  • Phenotype: physical appearance (Black)

  • Heterosis: Genes are different, Dominant & Recessive (Bb)

  • Homozygous: both genes are the same (BB or bb)