Presentation on theme: "Genes Located on chromosomes Thousands found in each animal"— Presentation transcript:
1Genes Located on chromosomes Thousands found in each animal Control inherited characteristicsCarcass traitsGrowth rateFeed efficiencyTwo types of inherited traitsDominantRecessive
2Genes Dominant gene Hides the effect of another gene Polled condition in cattle is dominantThe gene is represented by a capital letterRecessiveGene that is hidden by anotherThe gene is represented by a lower case letter
3Genes Example: The dominant gene is written- P The recessive gene is written-pP= Polledp= horned
4Homozygous and Heterozygous Homozygous gene pairCarries two genes for a traitPolled cow might carry the gene PPHeterozygous (or hybrid)Carries two different genes that affect a traitPolled cows might carry a recessive gene with the dominant Pp
5Punnett Square P PP P= Polled p= horned Example: Two polled cattle that are homozygous for the polled traitPolled DamPPPPolled Sire
6Punnett Square N= Normal size n= Dwarfism Example: Normal size in cattle is dominant to dwarfismNormal DamNNNnNnSire Carrier
7Punnett Square N= Normal size n= Dwarfism Example: What if both parents are carriers for a trait or disorder?Normal DamNnNNNnnnSire CarrierResult: one out of every four births could result in a dwarf animal (1:2:1)
8Monohybrid CrossA monohybrid cross is an estimation of a predicted outcome for a single trait.If a homozygous horned cow (pp) is bred with a heterozygous polled bull (Pp), what percent of the calves will be polled?
9Dihybrid CrossA dihybrid cross is a estimation of a predicted outcome for two traits.What results if an Angus bull that is homozygous black and polled (BBPP) is bred with a red shorthorn cow which is homozygous red and horned (bbpp).The bull BBPP can be simplified to BP (black & polled is the only possible contribution for the bull).The cow bbpp can be simplified to bp (red & horned is the only possible contribution for the cow).
11Dihybrid CrossNow if two of the offspring which are heterozygous for black/red and polled/horned (BbPp) are mated.How do you do a Punnett square for two heterozyous animals?Use all possible gene combinations.Both the bull and cow are BbPp.What are the possible contributions?BP, Bp, bP, bp for both animals. (4 x 4 grid)
18AssignmentComplete a Punnett Square for two animals that are heterozygous for two traits:Polled=PBlack= B(Alternatives are horned and red)DamSire
19PracticeBlack is dominant (B), and red is recessive (b). "Predict the offspring from the cross of a red bull and a black cow if the black cow's mother was red".
20First things first: the only way for the red bull to be red (the recessive trait) is if it's genotype is homozygous recessive (2 little letters), so the red bull is "bb". Now, the black cow's genotype could be either "BB" or "Bb". If its mommy was red (bb), then this black cow MUST have inherited a little "b" from its mommy. So the black one in our cross is "Bb" (not "BB"), and our cattle cross is: Bb x bb.
21Heritability Objective: Discuss hertability estimates for beef and swine
22HeritabilityEstimated the likelihood of a trait being passes on from the parent to the offspringLow heritabilityslow herd improvementHigh heritabilityfaster improvement
23Heritability Swine rates are usually lower than cattle Heritiability for carcass traits are higher than reproductive traitsEstimates vary from 0 to 70%