46: Cat Tails

TEKS B.8B

TEKS B.8B

: Science concepts--mechanisms of genetics. The student knows the role of

nucleic acids and the principles of inheritance and variation of traits in Mendelian and non-

Mendelian genetics. The student is expected to predict possible outcomes of various genetic

combinations using monohybrid and dihybrid crosses, including non-Mendelian traits of

incomplete dominance, codominance, sex-linked traits, and multiple alleles.

Answer

Student 4 is correct.

When you cross two heterozygous parents, the potential offspring have the

following genotypic distribution.

Genotypic Distribution

Ratio

One TT: Two Tt : One tt

Fractions

¼ TT, ½ Tt, ¼ tt

Percentages

25% TT, 50% Tt, 25% tt

Teacher Notes

Representing genotypes and phenotypes in different ways is an important skill for students

to practice. Genotypes and phenotypes can be represented using percentages, ratios, and

fractions and may be displayed in a variety of graphical formats. If students are struggling to

work through this item, suggest that they first ignore all the answer choices and simply work

through the provided Punnett square to determine the probability of possible genotypes.

Then, prompt students to analyze the results while considering how those results could be

represented numerically in different ways. For example, if a student answers in a ratio, prompt

them to consider converting the ratio to percentages or fractions. Finally, students can then

compare their responses to the answer choices.