Maximum Score - 25 Points

Part 1

• Allow 1 point if the student selects the recessive trait.

• Allow 2 points if the student uses complete sentences to explain that parents in the F1 generation both lack the trait, but must have had hidden recessive unit factor for the trait since they had offspring with the trait.
• Allow 1 point if the student gives a correct explanation, but it is not in complete sentences.
• No credit for an incomplete explanation even if it is written in complete sentences.

• Allow 1 point fo reach correct genotype indicated (note: 2 points may be awarded for A1)

• Allow 1 point for each of the following if they are included in the student's explanation;
• Bernie must be pure since he shows the recessive trait.
• Both parents must have been hybrid since they did not have the trait but passed it to Bernie.
• A1 did not show the trait, but he may have received a dominant from both parents or a dominant from one parent and a recessive from the other.
• Allow 1 point if all correct statements are written in complete sentences.

Part 2

• Allow 1 point if the student selects the X chromosomes.

• Allow 1 point if the student selects the X chromosome.

• Allow 2 points if the student indicates knowledge that there is only one x chromosome in males and this allows a single recessive allele to be expressed.
• Allow 1 point if the student indicates only partial knowledge of the abov cause.
  ****Allow an additional 1 point if the students explanation is written in complete sentences.
• No credit given if the explanation is incorrect even if it is written in complete sentences.

• Allow 1 point for each of the following accounted for in their code;

  Male and female chromosome

  Trait only on the female chromosome
  Dominant and recessive form of the gene