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Dimples and DNA
In humans, dimpled cheeks are a dominant trait, DD or Dd. Nondimpled cheeks are a recessive trait, dd.
1. Imagine that Parent A, with the genotype DD, has dimpled cheeks. Parent B has the genotype dd
and has nondimpled cheeks. The Punnett square below diagrams the cross between Parent A and
Parent B. Complete the Punnett square. (The first square has been done for you.)
2. A Punnett square shows what genotypes are possible for the offspring of a certain cross. What
genotypes are possible for the offspring of the parents above?
3. Each of the four squares of a Punnett square represents 25% probability that the offspring will have
that genotype. What is the probability that the offspring for these parents have dimpled cheeks?
Patent X, with the genotype Dd, has dimpled cheeks. Parent Y also has the genotype Dd and has
dimpled cheeks. Complete the Punnett square below to determine their possible offspring.
4. What is the probability that the offspring for these parents will have the following genotypes?
Genotype %
DD
Dd
dd
5. What is the probability that the offspring for these parents will have nondimpled cheeks?
6. What is the probability that the offspring for these parents will have dimpled cheeks?
Vocabulary Garden
Write the word of phrase being described below in the appropriate space on the next page.
1. Chromosomes with matching information.
2. Carry genes that determine the sex of offspring
3. The two genes that govern the same characteristic
4. An organism’s inherited combination of alleles
5. Nuclear division in eukaryotic cells in which each cell receives a copy of the original chromosomes
6. The passing of traits from parents to offspring
7. Cell division that produces sex cells
8. Kind of trait that seemed to vanish in the offspring produced in Mendel’s first experiment
9. Tool used to visualize al lteh possible combinations of alleles from parents
10. Kind of trait that always appeared in the offspring produced in Mendel’s first experiment
11. A true-________________ plant always produces offspring with the same trait as the parents(s)
12. A self-________________ plant contains both male and female reproductive structures.
13. Male sex cells
14. An organism’s inherited appearance
15. Female sex cells
16. The mathematical chance that an event will occur
17. Located on chromosomes and carry hereditary instructions
What do Gregor Mendel’s peas have to do with the study of heredity?