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 a  ZW pair of chromosomes are always female (ZWf), while individuals with a  ZZ pair of chromosomes can be either male (ZZm) 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

Egg Incubation Temperature (°C)	ZZm×ZWf Crosses: Fraction of Female Progeny ±2SEX¯¯¯	ZZm×ZZf Crosses: Fraction of Female Progeny ±2SEX¯¯¯
23	0.5±.08	0
24	0.5±.02	0
26	0.5±.07	0
28	0.5±.03	0
30	0.5±.01	0.03±.01
32	0.5±.03	0.2±.02
33	0.58±.03	0.52±.05
34	0.74±.04	0.88±.04
35	0.93±.03	0.97±0.2
36	1.0±0.0	1.0±0.0

(a) If a particular gene is located on the  Z chromosome of this lizard species,  describe why a lizard with a  ZWgenotype has a greater probability of expressing the recessive phenotype for the trait than a lizard with the  ZZgenotype does.

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Question 2

(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×ZWf crosses and the  ZZm×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.

Question 3

(c) For each cross,  describe whether genetics or temperature determines the sex of progeny produced from eggs incubated at  35°C. For each cross,  describe whether genetics or temperature determines the sex of progeny produced from eggs incubated at  24°C.

Question 4

(d)  Predict the effect of increasing global temperatures on the continued presence of the  W 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

Qn-1  a)

If there is most control or common one of a pair of genes (allele)for a feature of a present on a similar in structure or position(homolgous) genetic information storage area (chromosome) to hide the recessive one of a pair of genes, the recessive phenotypre will be expressed. In this case, the tiny chemical assembly instructions inside of living things(gene) is located on the Zgenetic information storage area. In an individual with a ZWgenotype female, there is no similar in structure or position Z partner, meaning whatever one of pairof genes is present on the single alone Z genetic information storage area will be expressed.

Qn-3 c)

ZWfemales xZZ males at 24'C:

Half of the child or outcomes(progeny) are female. This is likey figured out by decided by the study of tiny chemical assembly instructions inside of living things(genes) as there is a 50/50 chance that the child inherit Z or W from mother, and always from father.

ZZ females XZZ males at 24'C:

None of the child or outcomes(progeny) are female. This is figured out by the study of tiny chemical assembly instructions inside of living things and temperature, as there are no W genetic information storage areas to pass on to the child, meaning all child will always be ZZ. At this temperature that means no ZZ females are produced.

ZZ females XZZ males at 35'C:

Almost all of the child or outcome(progeny) are female. This is likely temperature dependent, because there is equal possibility related to tiny chemical assembly instructions inside of living things that child could be male or female (inherit Z or W). However at higher temperatures ZZ child develop into female over males.

Qn-4 d)

At temperatures over 33'C, there is a sharp change towards female sex XX rather than males. The W genetic information storage area (chromosome) figure out a female, but it is not needed to do so. Increasing temperatures can also produce females. Therefore, the presence of the W chromosome wil likely reduce or even disappear completely and the group of similar living things  could just depend on temperature to figure out sex.

Scientists claim that, in this group of similar living things (species) the W genetic information storage area (chromsome). The W genetic information storage area is unimportant in sex strong desire. Instead, proteins that are translated or put into a secret code by a tiny chemical assemby instructions inside of iving things in the Z genetic information storage area and that are maximum expressed only at certain temperatures, are responsible for figuring out whether animals in very early stages life(embryo) will develop as males or females.