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Chapter 5: Problem 5

Distinguish between (a) the concepts of sexual differentiation and sex determination and (b) Protenor and Lygaeus modes of sex determination.

Short Answer

Expert verified
The main difference between the Protenor and Lygaeus modes of sex determination is the sex that is heterogametic. In the Protenor mode, males have different sex chromosomes (XY), while females have the same sex chromosomes (XX). In the Lygaeus mode, it is the opposite: females have different sex chromosomes (ZW), and males have the same sex chromosomes (ZZ).

Step by step solution

01

Definition of Sexual Differentiation and Sex Determination

Sexual differentiation is the process by which an individual's sex-related characteristics, such as genitals, internal reproductive organs, and secondary sexual characteristics, develop during gestation, childhood, and puberty. This process is influenced by genetic, hormonal, and environmental factors. Sex determination, on the other hand, is the process that determines the sex of an individual organism during its development, usually determined by its genetic makeup. The sex of an individual can be determined by various methods, such as chromosomal, genic, or environmental factors.
02

Difference between Sexual Differentiation and Sex Determination

To differentiate, sexual differentiation refers to the development of sex-specific characteristics of an individual, whereas sex determination refers to the process of determining an individual's sex based on its genetic makeup or other factors. In other words, sex determination leads to sexual differentiation.
03

Definition of Protenor and Lygaeus Modes of Sex Determination

The Protenor and Lygaeus modes of sex determination are two different systems of chromosomal sex determination found in insects. Protenor mode: In this system, the male has a heterogametic sex chromosome system (XY) and the female has a homogametic sex chromosome system (XX). This mode of sex determination is similar to the one found in humans and most mammals. Lygaeus mode: In this system, the female is heterogametic (ZW), and the male is homogametic (ZZ). This mode of sex determination is found in some insects, birds, and reptiles.
04

Comparison of Protenor and Lygaeus Modes

The main difference between the Protenor and Lygaeus modes of sex determination is the sex that is heterogametic. In the Protenor mode, males have different sex chromosomes (XY), while females have the same sex chromosomes (XX). In the Lygaeus mode, it is the opposite: females have different sex chromosomes (ZW), and males have the same sex chromosomes (ZZ).

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Most popular questions from this chapter

How do mammals, including humans, solve the "dosage prob- lem" caused by the presence of an \(\mathrm{X}\) and \(\mathrm{Y}\) chromosome in one sex and two X chromosomes in the other sex?

Under what circumstances can a male cat exhibit a tortoiseshell coat pattern?

A group of scientists developing an XX zygote in vitro are curious to see the impact of certain chemicals on the development of the said organism. They incubate the zygote with the help of testosterone and some transcription factors, which are usually produced by the activity of the Y chromosome. They discover that the zygote develops into a sterile female with masculinized reproductive organs. Explain why this happens.

In this chapter, we have focused on sex differentiation, sex chro- mosomes, and genetic mechanisms involved in sex determination. At the same time, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, you should answer the following fundamental questions: (a) How do we know that in humans the X chromosomes play no role in sex determination, while the Y chromosome causes maleness and its absence causes femaleness? (b) How did we originally (in the late 1940 s) analyze the sex ratio at conception in humans, and how has our approach to studying this issue changed in \(2015 ?\) (c) How do we know that \(X\) chromosomal inactivation of either the paternal or maternal homolog is a random event during early development in mammalian females? (d) How do we know that Drosophila utilizes a different sexdetermination mechanism than mammals, even though it has the same sex-chromosome compositions in males and females?

It is believed that any male-determining genes contained on the Y chromosome in humans are not located in the limited region that synapses with the X chromosome during meiosis. What might be the outcome if such genes were located in this region?
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