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Gregor Mendel got the following results in his investigations on peas: Character Cross Number counted Number counted Shape of seed round x wrinkled 4832 round 0 wrinkled Shape of seed round x round 5474 round 1850 wrinkled Explain the results using genetic diagrams and comment on how close the results were from the expected outcome. Give evidence from the family tree that night blindness could be a recessive condition. Suggest genotypes for individuals 5,6,12,13 and 14. Give evidence from the family tree that PTC tasting must be the result of a dominant allele. 1 2 3 4 5 Parent phenotype Parent phenotype Offspring phenotype tall plants short plants 1012 tall plants tall offspring from cross 1 tall offspring from cross 1 787 tall 277 short all parents were self fertilised tall offspring from cross 2 some gave only tall plants but most produced tall and short plants all parents were self fertilised short offspring from cross 2 all the offspring were short stemmed tall offspring from cross 1 short plants 467 tall 483 short A pedigree Highland bull always produces offspring that are black. A second pedigree bull sometimes produces offspring that are brown. Suggest a hypothesis to explain these observations. Briefly describe a way to test your hypothesis. In fruit flies, normal wings are produced by the dominant allele M and miniature wings by the recessive allele m. In an experiment, a purebreeding female fly with normal wings was crossed with a male having miniature wings. All the offspring had normal wings. When these offspring were allowed to interbreed, the following results were obtained: 105 females, with normal wings 52 males, with normal wings 46 males, with miniature wings Give a reasoned explanation for the results. A recessive mutant allele of a gene responsible for the synthesis of chlorophyll in the tomato gives an albino plant when homozygous. The albino dies in the seedling stage after using up the food reserves in the seed. Heterozygotes give pale-coloured plants, but they survive. A normal green tomato plant was crossed with a heterozygote and the seed harvested. These seeds were planted and gave rise to progeny which were then selfpollinated. A further generation was grown using this selfed seed and the progeny were found to be a mixture of normal green and pale-coloured plants in a ratio of 5:2. Explain these results. The inheritance of coat colour in cattle involves a multiple allelic series with a dominance hierarchy as follows: S > sh > sc > s The S allele puts a band of white colour around the middle of the animal and is referred to as a ‘Dutch belt’; the sh allele produces ‘Hereford’ type spotting; solid colour is a result of the sc allele; and Holstein-type spotting is due to the s allele. Homozygous Dutch-belted males are crossed to Holstein-type spotted females. The F1 females are crossed to Hereford-type spotted male of genotype shsc. Predict the genotypic and phenotypic frequencies in the offspring. Tomato plant leaves show variation in colour and shape. Leaves can be green or purple and their edges can be cut or uncut. The gene controlling leaf colour has two alleles; P (producing purple) and p (producing green colouring). The gene controlling leaf shape also has two alleles; C (producing a cut edge) and c (producing an uncut edge). A plant with Purple, cut leaves was crossed with a green, uncut plant. All the offspring had purple, cut leaves. Predict the outcome if two of these offspring were crossed. Coat colour in Galloway cattle is controlled by a gene with two alleles. The R allele produces red hairs and therefore a red coat colour. The r allele produces white hairs. A farmer crossed a truebreeding, red-coated cow with a true-breeding white-coated bull. The calf produced had roan coat colouring (composed of an equal number of red and white hairs). Explain the result and draw a genetic diagram to predict the outcome of crossing two roan coloured animals.