GENETICS OF ANIMAL BREEDING

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GENETICS OF ANIMAL BREEDING

• UNIT 9
• AGRICULTURE PRODUCTION

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GENETICS--

• STUDY OF HEREDITY
• OR THE WAY IN WHICH TRAITS OF PARENTS ARE PASSED
  ON TO THE OFFSPRING
• GREGOR MENDEL--1ST PERSON TO STUDY
  GENETICS--GARDEN PEAS

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ADAPTATION VS HERITABILITY

• ADAPTATION --SOME DIFFERENCES CAN BE CAUSED BY
  ENVIRONMENT OR CONDITIONS THAT THE ANIMALS ARE
  RAISED.
• HERITABILITY--AMOUNT OF DIFFERENCE BETWEEN
  ANIMALS THAT IS PASSED FROM THE PARENTS.

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HERITABILITY ESTIMATE--

• LIKELIHOOD OF THE DIFFERENCE BEING PASSED FROM
  THE PARENTS TO THE OFFSPRING.
• EX. BIRTH WT.--40
• CARCASS LENGTH--60
• CAN VARIES WITH SPECIES AND BREEDS OF ANIMALS

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CELL AND CELL DIVISION

• CELLS MAKES UP THE ANIMALS--ALWAYS CHANGING
• NUCLEUS--CENTER OF THE CELL PROTOPLASM
• ABILITY TO GROW, DIGEST FOOD AND DIVIDE
• CYTOPLASM--SURROUNDS THE NUCLEUS
• CELL WALL--CONTAINS THE CELL MATERIALS

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CELL AND CELL DIVISION

• It assembles proteins and other molecules to do
  work.
• TERMS TO KNOW
• cytoplasm
• nucleus
• Golgi complex
• mitochondria
• endoplasmic reticulum
• ribosomes
• lysosomes

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CHROMOSOMES--FOUND WITHIN NUCLEUS

• ROD SHAPE
• MADE OF PROTEIN
• FOUND IN PAIRS EXCEPT IN SPERM EGG CELLS
• PAIRS--CATTLE--30 SWINE--19 SHEEP--27
  HORSES--33 CHICKENS-6, HUMANS 23
• ONE PAIR FROM THE FATHER ONE PAIR FROM THE
  MOTHER.

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PARTS OF THE CELL

• The cytoplasm is the liquid material outside the
  nucleus where the other parts of the cell are
  found and formed.
• The nucleus holds the material that decides
  whether you have blue or brown eyes, whether you
  can roll your tongue, and other important things.
  This material is called DNA (deoxyribonucleic
  acid--whew!). DNA carries instructions that tell
  the cell how to make protein molecules.
• The Golgi complex is where molecules are finished
  off and packaged. Cells that do a lot of
  secreting have very busy Golgi complexes.
• The mitochondria (say "mite-o-kon'-dree-a") are
  the engines of the cell. They make stored energy
  available to the cell.

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Parts of the Cell

• The endoplasmic reticulum (say "en-doe-plaz'-mik
  re-tik-u-lum") is where a lot of the chemical
  activity of the cell takes place.
• The ribosomes make proteins. They are found on
  the outer part of the endoplasmic reticulum.
• The lysosomes defend the cell from invaders.
• If bacteria invade the cell, lysosomes release
  enzymes that eat them.
• Lysosomes help break down the cell when it dies.

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MITOSIS--

• CHROMOSOME PAIRS ARE DUPLICATE IN EACH NEW CELL.
• ALL NEW CELLS ARE EXACTLY LIKE THE OLD CELLS
• HAPPENS INSIDE THE BODY--HOW THE ANIMALS GROWS BY
  INCREASING THE NUMBER OF CELL

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MEIOSIS--

• FOUND IN REPRODUCTION NEW CELLS ARE NOT THE
  SAME AS OLD CELLS
• GAMETE--REPRODUCTION CELLS (SPERM OR EGG CELLS)
• WHEN MATURE GAMETE DIVIDES, CHROMOSOME CELLS
  SEPARATE ONE CHROMOSOME OF A PAIR GOES TO THE OLD
  CELL AND ONE TO THE NEW CELL.

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AFTER MEIOSIS,

• EACH GAMETE HAS ONE HALF THE ORIGINAL NUMBER OF
  CHROMOSOMES. THESE ARE DIVIDED BY MITOSIS.
• FOUR SPERM CELLS FOR EACH ORIGINAL SPERM CELL
• FOUR EGGS THREE WHICH DO NOT FUNCTION.

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FERTILIZATION--

• UNION OF SPERM AND EGG TO EQUAL COMPLETE CELL
• THE ANIMAL NUMBER OF CHROMOSOMES ARE ESTABLISHED
• DIFFERENT COMBINATION OF TRAITS CAN HAPPEN

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GENES--

• COMPLEX MOLECULES LOCATED ON THE CHROMOSOME.
• FOUND IN PAIRS
• CONTROL MOST TRAITS IN ANIMALS

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ADDITIVE GENE EFFECT-- EX. SWINE CARCASS

• CONTROL A TRAIT BY THE NUMBER OF GENES WHICH
  ARE PRESENT. EACH GENE TRAIT ADDS TO ITS
  PRESENCE THE EFFECT OF EACH PAIR IS SEPARATE.
• THE EFFECT OF ALL OF THE PAIRS FOR THIS TRAIT
  ADDS UP TO DETERMINE THE STRENGTH OF THE TRAIT
• USUALLY HIGH HERITABILITY

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NONADDITIVE GENE EFFECT--

• HOW GENES ACT IN DIFFERENT COMBINATION WITH ONE
  ANOTHER.
• WHEN GENE PAIRS GIVE GOOD EFFECTS, THE OFFSPRING
  WILL BE BETTER THAN THE PARENTS
• THIS IS CALLED HYBRID VIGOR OR HETEROSIS

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DOMINANT GENE--

• HIDES THE EFFECT OF THE OTHER GENE
• REPRESENTED BY A CAPITAL LETTER
• RECESSIVE GENE--GENE THAT IS HIDDEN
• REPRESENTED BY A SMALL LETTER

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HOMOZYGOUS VS HETEROZYGOUS GENE

• HOMOZYGOUS GENE PAIR--CARRIES TWO LIKE GENES FOR
  A TRAIT
• HETEROZYGOUS GENE PAIR--CARRIES TWO DIFFERENT
  GENES FOR A TRAIT

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GENE PAIRS

• HOMOZYGOUS GENE PAIR--CARRIES TWO GENES FOR A
  TRAIT
• PP FOR HORNED CATTLE
• HETEROZYGOUS GENE PAIR--CARRIES TWO DIFFERENT
  GENES FOR A TRAIT
• Pp FOR POLLED CATTLE

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GENOTYPE--

• KINDS OF GENES PAIRS POSSESSED BY THE ANIMAL
• CHECKER BOARD
• GENOTYPIC RATIO

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PHENOTYPE--

• PHYSICAL APPEARANCE OF THE ANIMAL
• PHENOTYPIC RATIO

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INCOMPLETE DOMINANCE--

• ONE GENE DOES NOT HIDE OR MASK THE EFFECT OF THE
  OTHER GENE IN GENE PAIR--gt RESULTS IN MIXTURE OF
  THE TWO TRAITS.
• EX. ROAN COLOR (RW)

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SEX DETERMINATION--MAMMALS-FERTIIZATION

• FEMALES--XX CHROMOSOMES (2 SEX CHROMOSOMES)
• MALES--XY CHROMOSOMES (1 SEX CHROMOSOME)
• AFTER MEIOSIS, ALL EGGS HAVE A X CHROMOSOME ONLY
  1/2 OF THE MALE WILL HAVE A X CHROMOSOME
• OTHER 1/2 OF THE MALE WILL BE Y CHROMOSOME

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BIRD--FEMALES DETERMINE THE SEX

• MALES--ZZ CHROMOSOMES (2 SEX CHROMOSOMES)
• FEMALES--ZW CHROMOSOMES (1 SEX CHROMOSOMES)
• AFTER MEIOSIS ALL MALES WILL HAVE A Z CHROMOSOME
  
• 1/2 EGGS WILL HAVE A Z CHROMOSOME

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SEX LINKED CHARACTERISTIC--

• GENES WHICH ARE CARRIED ONLY ON THE SEX CELLS
• BARRED COLOR IN CHICKENS

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LINKAGE--

• CERTAIN TRAITS TO APPEAR IN GROUPS.
• CLOSER THEY ARE LOCATED ON CHROMOSOMES MOST
  LIKELY THEY WILL STAY TOGETHER

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CROSSOVER--

• GENES LINE UP, DURING MEIOSIS, CHROMOSOMES CROSS
  OVER ONE ANOTHER AND SPILT TO FORM A NEW
  CHROMOSOMES WITH A DIFFERENT COMBINATION
• THE FARTHER CHROMOSOMES ARE APART-THIS WILL
  OCCUR.

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MUTATION--

• SOMETHING CAUSES THE GENE TO CHANGE
• NEW TRAIT IS SHOWN WHICH DID NOT EXIST IN EITHER
  PARENT--POLLED CATTLE
• PASSED ON TO THE OFFSPRING
• SOME ARE HARMFUL, SOME MAY BE BENEFICIAL