PreAP WORKSHEET DIHYBRID INHERITANCE 1-9 NOVAK
PAPWsDihybridInheritance1-9
PROBLEM 1. In Drosophila, cross veinless wings and ebony body color are due to two separate recessive genes that are autosomal. The dominant alleles are normal (wild) veined wings and normal (wild) body color What genotype of offspring would you expect from a cross between a cross veinless ebony female and a homozygous wild (normal-winged, normal body color) male? 1a...... What would the phenotype of the F1 flies be? 1b...... If the F1 are allowed to breed among themselves, what types of offspring would you expect in the F2? (express your answer as a fraction) wild;wild 2...... wild winged;ebony body color 3...... cross veinless;wild body color 4...... cross veinless;ebony color 5...... What fraction of the F2 offspring would have all four dominant genes? 6......
PROBLEM 2. To be sure a gene is recessive, geneticists sometimes do what is called a test cross. This is done by crossing the F1 offspring from P1 pure parents to individuals that are homozygous recessive (for both pair of genes in the case of dihybrid inheritance). If you made a test cross of the F1 males of the preceding problem what results would you expect to obtain? (express your answer as a fraction) wild;wild 7...... wild winged;ebony body color 8...... cross veinless;wild body color 9...... cross veinless;ebony color 10...... What fraction of the offspring would have all four dominant genes? 11...... In a testcross, is the ratio of phenotypes the same as the ratio of genotypes? 12...... What per cent of the offspring in this testcross was a double hybrid? 13......
PROBLEM 3. If a cross veinless-winged female who is heterozygous for normal body color is crossed with and ebony body colored male who is heterozygous for normal wings, what types of offspring would you expect in the F1? (express your answer as a fraction) wild;wild 14...... wild winged;ebony body color 15...... cross veinless;wild body color 16...... cross veinless;ebony color 17......
PROBLEM 4 In tomatoes, yellow fruit and dwarfed vine are due to recessive genes. Their alleles produce the more common red fruit and tall vine. Pollen from a pure-line dwarf plant bearing red fruit is placed on the pistil of a pure-line tall plant bearing yellow fruit. What phenotypes would be expected in the F1? 18...... What would the genotype of the F1 be? 19...... If an F2 is produced, give the ratio (expressed as a fraction) of the following phenotypic combinations: red;tall 20...... red;dwarf 21...... yellow;tall 22...... yellow;dwarf 23...... In this typical F2 situation, what is the most frequent genotype? 24...... In this typical F2 situation, how many genotypes would you expect to occur only once in sixteen times? 25...... In the F2, how many different genotypic combinations are possible? 26......
PROBLEM 5. About 70% of Americans get a bitter taste from a drug, phenylthiocarbamide (PTC); the others do not. The ability to taste this drug results from a autosomal dominate gene while taste-blindness is recessive. The gene for normal body color is due to an autosomal dominated gene located on a chromosome separate from the chromosome that carries the gene for tasting PTC. A normally pigmented woman who is taste-blind has a father who is an albino-taster. She marries an albino man who is a taster, but who has a mother who is taste-blind. Express the following possible phenotypic combinations in the children as a fraction: normal;taster 27...... normal;taste-blind 28...... albino;taster 29...... albino;taste blind 30...... With this woman and her husband, how many genotypic combinations were NOT possible compared to the F2 genotypic combinations possible in problem 4? 31......
PROBLEM 6 In the domestic swine, the autosomal gene for a white belt around the body is dominate to the gene for a uniformly (or solid) colored body. Some hogs have a abnormal fusion of the two elements of their hoof to produce the mule-footed condition (syndactyly). This also results from a autosomal dominate gene separate from the gene for body color. What does autosome mean? 32...... What (expressed as a fraction) would be the phenotypic combinations between a hybrid belted normal footed male and a hybrid mule-footed solid colored female: belted;mule-footed 33...... belted normal foot 34...... solid;mule-footed 35...... solid normal foot 36...... A farmer wishes to raise only belted swine with normal feet, but there are some solid-colored and some mule footed hogs in his pens. How would you advise him to proceed in his efforts to establish pure-breeding, belted hogs with normal feet? 37 ......
PROBLEM 7. Some dogs bark when trailing; others are silent. The barking trait is due to a autosomal dominate gene. Erect ears are autosomal and dominate to drooping ears. What kind of pups would be expected from a heterozygous erect-eared barker male mated to a droop-eared, silent trailer female? (Give answer in the form of a fraction) erect;barker 38...... erect silent 39...... droop-eared;barker 40...... droop-eared;silent 41...... How many different genotypic combinations are possible in this cross? 42......
PROBLEM 8. In certain strains of chickens some individuals turn out to be blue in color. This blue condition is known as Andalusian and has been found to be intermediate between the gene that causes black and the gene that causes splashed white chickens. Rose comb is dominant to single comb in chickens and is on a separate chromosome from the gene causing feather color. What type of offspring would be expected from a splashed-white rooster who is heterozygous rose-combed, crossed with a single-combed, blue Andalusian hen? Out of sixteen offspring, how many would you expect to be; blue;rose 43...... blue;single 44...... white;single 45...... white;rose 46...... black;rose 47...... black single 48...... How many different phenotypic combinations would be possible if you crossed a splashed white rose combed F1 hen with a black single combed male? 49......
PROBLEM 9. In problem 1, would you get the same ratios of phenotypes and genotypes in the F1 and F2 if you had crossed a cross veinless winged pure normal eye female with a pure normal winged ebony bodied male? 50...... What is the ratio in the F2 of the phenotypes in this problem? 51...... Is this the same phenotypic ratio that you received in the F2 of problem 1? 52......
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