Ai manual chapter 10
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The document discusses heredity and genetics in cattle. Key points include: - Genes located on chromosomes determine hereditary traits such as hair color and milk production. Cattle have 30 pairs of chromosomes. - Outbreeding is highly recommended to increase heterozygous gene pairs and avoid issues from undesirable recessive genes, while inbreeding can increase homozygous gene pairs and expression of recessives. - Traits are influenced by many gene pairs on different chromosomes. Some genes are dominant and affect simple traits.
Ai manual chapter 10
- 1. CHAPTER 10 HEREDITY & HOW IT WORKS
- 2. Genetic Principles Gene = Unit of Inheritance Determines Hereditary Characteristics I.E. Hair Color, Milk Production, Rate of Gain Segment of a Chromosome Chromosome Located in Nucleus of a Body Cell 30 Pairs of Chromosomes in Cattle
- 4. Cellular Replication Tissue Growth Occurs When Body Cells Duplicate and Divide Chromosomes Replicate Themselves Exactly Duplicate Chromosomes Separate One Pair Goes to Each of the Two New Cells New Cells Contain Same Number of Chromosomes as the Parent Cells
- 5. Gamete and Zygote Formation Different Process Chromosomes Separate One Chromosome Goes to Each Gamete Gamete = New Daughter Cell Contains Half of Hereditary Units of its Parent Fertilization or Conception Union of Male (Sperm) and Female (Egg) Gametes Zygote = Fertilized Egg Single Living Cell Containing Newly Paired Chromosomes Contains all Hereditary Units for the New Individual
- 6. Gamete and Zygote Formation
- 7. What Cells Become Determining Factor DNA (Deoxyribonucleic Acid) Spells Out What Cells Should Do and When to Do it Stores Hereditary Information Passes Information to Cells by Chemical Messengers called RNA (Ribonucleic Acid). Messages Direct Specific Genes to Remain Active While Others are Inactive
- 8. Genes Come in Pairs Same = Homozygous Genes Different = Heterozygous Genes Dominant = One Gene Overshadows the Other I.E. Polled (Hornless) is Dominant Over Horns Recessive = Gene That is Not Dominant Trait Only Evident When Genes are Homozygous Genotype = Actual Genes an Animal Has Phenotype = Characteristic an Animal Displays
- 11. Gene Characteristics Not all Gene Pairs Have a Dominant Gene Produce a Blend in the Phenotypic Expression I.E. Roan Hair Color in Shorthorn Cattle Not all Genes are Visually Identical Chromosomes that Determine Gender Longer Chromosome = X Shorter Chromosome = Y XX = Female Offspring XY = Male Offspring
- 12. Chromosomes That Determine Gender
- 13. Inheritance is Complicated Different Gene Pairs Can Affect Same Trait I.E. Milk Production and Rate of Gain Genes May Also Switch Places Within a Pair Called Crossing Over Mutation Can Affect a Genes Chemical Code These Types of Changes are Very Rare Environmental Factors Can Influence Gene Expression and Inheritance Affects From Conception to Maturity
- 14. Outbreeding Increases Frequency of Heterozygous Gene Pairs Most Practical and Highly Recommended Outcrossing Mating Same Breed but Unrelated Animals Cross-breeding Mating Different Breed Animals Hybrid Cross Mating of Different Species (Usually Sterile) Linecrossing Mating Animals of Different Inbred Lines
- 15. Inbreeding Increases Frequency of Homozygous Gene Pairs Closebreeding Mating of Closely Related Animals I.E. Sire to Daughter, Son to Dam, or Brother to Sister Linebreeding Mating of Less Closely Related Animals I.E. Half Brother to Half Sister or Cousin to Cousin Also Refers to Using Successive Descendants of a Specific Bull or Cow Use Only the Best Animals Offspring Genotypes Will Become More Alike Undesirable Recessives Are More Likely to be Expressed
- 18. Specific Conditions Albinism Congenital Condition Absence of Normal Pigments in the Hair, Skin and Eyes Sensitivity to Bright Light and Light Blindness Syndactylism (Mule Foot) Congenital Condition Claws of the Foot are Partially or Totally United Results in Some Lameness Poor Tolerance to High Atmospheric Temperatures Should be Vealed as Calves
- 19. Non-congenital Defects Porphyria (Pink Tooth) Abnormalities in Red Blood System Cause Pink Color in Teeth and Bones Sunlight Causes Skin to Appear Burned, Scabby and Hairless Urine May be Dark Animals Become Anemic and Unthrifty Affected Calves Should be Disposed of Early
- 20. Summary Genes Determine Hereditary Characteristics Genes are Located on Chromosomes Homozygous = Pairs of Same Genes Heterozygous = Pairs of Different Genes Some Genes are Dominant and Affect Simple Traits Most Economically Important Traits are Affected by Many Genes on Different Chromosomes
- 21. Summary Outbreeding is Highly Recommended Outcrossing Cross-breeding Hybrid Crosses Linecrossing Inbreeding Closebreeding Linebreeding Avoid Undesirable Recessives
- 22. Question 1 How many chromosome pairs do cattle have in nearly all of their body cells? 30
- 23. Question 2 How many chromosomes are present in sperm? In eggs? 30 chromosomes non-paired 30 chromosomes non-paired
- 24. Question 3 What happens when a black and white Holstein with the genes “BB” is mated to a red and white Holstein with the genes “bb”? What happens if one of their offspring is mated to a red and white Holstein with genes “bb”? All of the offspring will be red carriers “Bb”. Half of the offspring will be red carriers “Bb” and half of the offspring will be red “bb”.
- 25. Question 4 Describe how outbreeding differs from inbreeding. Outbreeding occurs when one is mating animals that are unrelated, whether they belong to the same breed or not. Inbreeding occurs when one is mating animals that are directly related or closely related.
- 26. Question 5 Define the following terms: Outcross Cross-breeding Hybrid Cross Linecrossing Mating unrelated animals of the same breed Mating animals of different breeds Mating animals of different species Mating animal of different inbred lines
- 27. Question 6 What is meant by “undesirable recessive”? Give several examples of these traits. An undesirable recessive means that it is a rare trait that negatively impacts animal health and on-farm profitability. Albinism, syndactylism (mule foot), porphyria (pink tooth)
- 28. Question 7 What kind of breeding program should be used to avoid congenital defect problems transmitted by recessive genes? Outbreeding
Editor's Notes
- #2: The quantity and quality of milk and meat are largely determined by inheritance. To make good genetic selections we need to have a basic understanding of heredity.
- #3: Genes are the units of inheritance determining an individual’s characteristics. Each gene is a segment of a thread like structure called a chromosome. Cattle have 30 pairs of chromosomes, a hog has 19, man has 23.
- #4: Where there once was one cell there are now two.
- #5: Cells dividing and multiplying is what cause the animal to grow and produce.
- #6: To reproduce the species, a different process occurs. Here the male (sperm) and the female (egg) have one of each pair of chromosomes. When fertilization happens the one from the male and the one from the female pair-up, forming all the hereditary units for the new individual.
- #7: Note the pairs in the fertilized egg.
- #8: DNA tells cells what to do and when to do it. Stores and passes on hereditary information by using chemical messengers (RNA).
- #9: Remember genes come in pairs; they can be homozygous or heterozygous. Some are dominant, others recessive. Every animal is made up of genotype and phenotype. Genotype = what it inherited. Phenotype = what the animal exhibits: udder shape, production, growth − that can be seen and measured.
- #10: This diagram shows what happens when the dominant gene for polled is homozygous in one parent and the recessive gene for horned is homozygous in the other are mated. All the offspring will be polled.
- #11: Here’s what happens when heterozygous parents carrying both the polled and horned gene are mated. Phenotypically 3 out of 4 will be polled 1 will be horned. Genetically 1 will be homozygous polled, 2 will be heterozygous polled and the horned one will be homozygous.
- #12: Not all pairs contain a dominate gene. The sex determining gene is one.
- #13: Every egg contains an x chromosome and each sperm contains either an x or y chromosome. If the egg is fertilized by the sperm containing the x we get a female, if it contains the y we get a male.
- #14: Inheritance is not as simple as xyz. Most economically important traits are affected by many different pairs of genes. In the end thousands of pairs of genes will determine the outward appearance of the animal. The environment such as nutrition and disease can influence the expression of those genes.
- #15: Basic systems are Outcrossing, Cross-breeding, and Linecrossing.
- #16: Inbreeding is breeding related animals to increase uniformity. Closebreeding is the mating of closely related animals such as son to dam, sire to daughter, brother to sister. Linebreeding is mating less closely related individuals such as cousins, etc. This system is recommended only for those who are in a position to cull rigidly and can withstand possible losses. Inbreeding is a tool that is useful for identifying superior families and testing for genetic defects.
- #17: Both the environment and genetics can cause congenital birth defects. This is an example of what happens when a parent carrying the undesirable recessive gene, but not exhibiting the trait is mated to one without the recessive gene. The results are 2 of 4 offspring will not carry the undesirable recessive and two will.
- #18: Here’s what happens when the mates both carry the undesirable gene but not the trait. Two out of four of the offspring will be carriers. One will not have the recessive. And one will exhibit the trait.
- #19: More common congenital conditions controlled by genetics.
- #20: Non-congenital defects are those that are not prevalent at birth but appear later as the calf grows.