BI3.2 Biology Reassessments

Catechol, a natural substance found in plants, reacts with oxygen to produce (see rest). (a) On the axes provided, construct an appropriately labeled bar graph to analyze the effect of pH on polyphenol oxidase activity.

(a) -Label axes correctly -Scale axes correctly -Plot data correctly where pH is the independent variable

(a) Based on a pedigree of a family in which one parent has Loeys-Dietz syndrome, a researcher claims that the disorder is an autosomal dominant condition. Describe TWO characteristics of the pedigree that would support this.

(a) -The characteristic is likely to be autosomal if it is inherited equally by males and females -Evidence to support dominant inheritance is if each individual has one or more affected parent

(b) Calculate the minimum number of nucleotides required in the coding region of the LDS2B mRNA molecule to produce and terminate the 565-amino acid polypeptide. Provide two reasons that the number of nucleotides in the mature mRNA may differ from the number of base pairs in the gene.

(b) *Calculations:* 565 x 3 = 1695 (Because there is a triplet code in the production of polypeptide) 1675 + 3 = 1698 (Because the stop codon should also be included in the sequence) *Reasoning:* This is because: - Introns are removed from the mRNA but remain in the gene structure - The gene has regulatory enhancers such as promoters that are not transcribed

(b) Based on the experimental results, estimate the optimal pH of the enzyme. Explain your results by connecting the results to the structure and function of proteins.

(b) The optimal pH of enzyme is 7 Evidence: -Other pH values produced less product Reasoning: -This is because a change in pH denatures the enzyme, thus reducing it's activity

(c) One genetic change associated with the disorder results in a methionine to valine substitution at amino acid 425 of the encoded polypeptide, as shown in Figure 1. Predict the DNA mutation that will result from this substitution.

(c) AUG -> GUG

(c) Propose an appropriate control treatment for the experiment, and describe how the control treatment would increase the validity of the results.

(c) The control treatment could be a reaction without the enzyme, to confirm that the enzyme is necessary to the experiment

(d) Propose three features of a model to connect the genetic mutation you predicted with the activity of the signaling pathway involving a LDS2B gene product

(d) -Change in the genetic sequence may decrease the function of the signaling pathway -It also may activate signaling instead -Will cause a structural change in the polypeptide

(d) Genetic engineering can be used to disrupt specific genes [...]. Predict how the browning of apple slices would be affected in a strain of apples that was genetically engineered to lack functional copies encoding polyphenol oxidase. Justify your response.

(d) Prediction: Fruit will not brown Reasoning: The browning of fruit requires a functional enzyme