Question

 Read each question carefully. Write your response in the space provided for each part of each question. Answers must be written out in paragraph form. Outlines, bulleted lists, or diagrams alone are not acceptable and will not be scored.

 The sex of an organism is typically determined genetically, but environmental factors can also play a role. Scientists examined the roles of genes and environmental temperature in the sex determination of a lizard species. Individuals with aZW pair of chromosomes are always female (ZWf), while individuals with a ZZ pair of chromosomes can be either male (2Zm) or female (ZZf). Scientists mated ZWf or ZZf females with ZZm males and incubated the eggs produced in 20 clutches at temperatures ranging from 23'C to 36'C. When the young hatched, the scientists determined their sexes (Table 1). Among the eggs that did not hatch, the mortality of embryonic lizards was approximately the same for both males and females.

 Table 1. Fraction of female progeny produced as a function of egg incubation temperature

 (a) If a particular gene is located on the Z chromosome of this lizard species, describe why a

 (b) Using the template, construct an appropriately labeled graph, including error bars, to represent the data in Table 1. Based on the data, compare the ZZm x ZWf crosses and the ZZm x ZZf crosses to determine whether there is a significant difference between the two crosses in the fraction of female progeny produced at 24"C, 32'C, and 36°C.

 (c) For each cross, describe whether genetics or temperature determines the sex of progeny produced from eggs incubated at35'C. For each cross, describe whether genetics or temperature determines the sex of progeny produced from eggs incubated at 24'C.

 (d) Predict the effect of increasing global temperatures on the continued presence of theW chromosome in this species of lizard. Scientists claim that, in this species, the W chromosome is unimportant in sex determination. Instead, proteins that are encoded by a gene or genes on the Z chromosome, and that are maximally expressed only at certain temperatures, are responsible for determining whether embryos will develop as females or males. Use the data to support this claim.

Answer 1

ANSWER 1.B :-