Write in composition book Punnet Square Notes Write in composition book

Phenotype the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Genotype the genetic constitution of an individual organism.

Dominant An allele or a gene that is expressed in an organism’s phenotype, masking the effect of the recessive allele or gene when present when paired with an identical or different allele.

Recessive a gene whose phenotypic expression is masked by a dominant gene, is only expressed when the same allele is present

Homozygous  When an individual has two of the same allele, whether dominant or recessive AA or aa

Heterozygous a pair of genes where one is dominant and one is recessive — they're different. Aa

Punnet Square  a diagram that is used to predict an outcome of a particular cross or breeding experiment.

#1 Let's say that in seals, the gene for the length of the whiskers has two alleles.  The dominant allele (W) codes long whiskers & the recessive allele (w) codes for short whiskers. a)  What percentage of offspring would be expected to have short whiskers from the cross of two long-whiskered seals, one that is homozygous dominant and one that is heterozygous?  b) If one parent seal is pure long-whiskered and the other is short- whiskered, what percent of offspring would have short whiskers?

#2 In purple people eaters, one-horn is dominant and no horns is recessive. Draw a Punnet Square showing the cross of a purple people eater that is hybrid for horns with a purple people eater that does not have horns. Summarize the genotypes & phenotypes of the possible offspring.

#3 A green-leafed plant is crossed with a plant with yellow-striped leaves.  The cross produces 185 green- leafed plants. Summarize the genotypes & phenotypes of the offspring that would be produced by crossing two of the green-leafed plants obtained from the initial parent plants.

#4 Mendel found that crossing wrinkle-seeded plants with pure round-seeded plants produced only round-seeded plants. What genotypic & phenotypic ratios can be expected from a cross of a wrinkle-seeded plant & a plant heterozygous for this trait (seed appearance)