Presentation on theme: "Final Concepts for Chapter 11 Mendelian Genetics"— Presentation transcript:
1Final Concepts for Chapter 11 Mendelian Genetics CodominanceComplete dominanceDihybrid crossGenotypeGenotypic ratioHeterozygousHomozygousIncomplete dominanceMonohybrid crossPhenotypePhenotypic ratioProbabilityPunnett squareTestcrossExpected/predicted resultsActual/observed resultsKaryotypeAmniocentesisLinked genesSex-linked disordersAutosomal disordersAlleleDominantRecessiveP-generationF1 generationF2 generationLaw of independent assortmentLaw of segregationChromosomesPure breedTrait
2Independent Assortment vs. Linked Genes Mendel did not know about chromosomes when he proposed the Law of Independent Assortment.The pea traits he studied happened to be located on different chromosomes – so they did assort independently.
3Independent Assortment vs. Linked Genes Question: How many traits do you have?Question: How many chromosomes (per cell) do you have?Question: Is it possible to have only one trait per chromosome?No, lots of genes are carried or linked together on the same chromosome.
4Independent Assortment vs. Linked Genes Do the punnett square for the following cross – assume independent assortment.Cross two heterozygous tall, heterozygous red flowered plantsT=tall R=red flowert= short r = white flower
5Independent Assortment vs. Linked Genes What is the phenotypic ratio?TtRr x TtRrTRTrtRtrTTRRTTRrTtRRTtRrTTrrTtrrttRRttRrttrrTRTrtRtr
6Independent Assortment vs. Linked Genes 9:3:3:1 ratio9 = tall and red3 = tall and white3 = short and red1 = short and whitePROBABILITY:From this cross, 48 offspring were produced.How many offspring would you expect to be tall and red?How many would expect to be tall and white?How many would you expect to be short and white?
7Independent Assortment vs. Linked Genes Now, do the following cross BUT the genes for tallness and red flowers are linked.Cross two heterozygous tall, heterozygous red flowered plantsT=tall R=red flowert= short r = white flower
8Independent Assortment vs. Linked Genes HintT tR rTtRr X TtRrIs it possible to produce a Tr gamete?
9Independent Assortment vs. Linked Genes TtRr X TtRrWhat is the phenotypic ratio?trTRTTRRTtRrttrr3:13 = Tall and Red1 = Short and whiteTRtr
10Independent Assortment vs. Linked Genes So… out of the 48 offspring, if the genes are linked, how many would be1. tall and red?2. tall and white?3. short and red?4. short and white?Answer:tall and red = 36 tall/white = 0short and white = 12 short/red = 0EXPECTED RESULTS!
11Independent Assortment vs. Linked Genes Is it possible for our Actual Results to show any flowers that are tall/white or short/red?Yes – how?Crossing over
12Crossing over occurs in meiosis Pieces of the chromosomes actual switch places.
14Codominance – the alleles are equally dominant Roan Cow Human Blood Type
15Fill in the genotypes on the pedigree. Sex-linked TraitsTraits carried on the X chromosomeFill in the genotypes on the pedigree.
16Autosomal disordersDisorders carried on non-sex chromosomes (first 22 pairs)Some are autosomal dominantHuntington’s diseaseMost are autosomal recessiveSickle-cell anemiaCystic fibrosis
17Question: How do you know if the pure bred dog you just paid big bucks for is actually pure? GG?Gg?
18Test CrossCross using a homozygous recessive individual with a dominant individual to determine if the dominant individual is heterozygous or homozygous dominant (pure)Why use a homozygous recessive individual?
19Test CrossDo the punnett squares for each case:GG x gg Gg x gg
20Test CrossAll offspring produced should show the dominant characteristics if the dominant parent is pure (GG) for the trait.