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Chapter 5: Problem 5

Distinguish between the Protenor and Lygaeus modes of sex determination.

Short Answer

Expert verified
Answer: The main difference between the Protenor and Lygaeus modes of sex determination lies in the gender that is heterogametic. In the Protenor mode, the female is heterogametic with ZW chromosomes, while in the Lygaeus mode, the male is heterogametic with XY chromosomes.

Step by step solution

01

Define the Protenor and Lygaeus Modes of Sex Determination

The Protenor and Lygaeus modes of sex determination are two different ways that sex is determined in insects in terms of chromosomal composition. Both systems involve the presence of one or more heterogametic mechanisms.
02

Characteristics of the Protenor mode of sex determination

In the Protenor mode of sex determination, the female is the heterogametic sex, having two different types of sex chromosomes, while the male is the homogametic sex, possessing two identical sex chromosomes. Females have Z and W chromosomes (ZW), while males have two Z chromosomes (ZZ). A female can produce two types of gametes carrying either the Z or W chromosome, while a male can produce only one type of gamete carrying the Z chromosome.
03

Characteristics of the Lygaeus mode of sex determination

In contrast, the Lygaeus mode of sex determination presents the male as the heterogametic sex, having two different types of sex chromosomes, while the female is the homogametic sex, possessing two identical sex chromosomes. Females have two X chromosomes (XX) while males have X and Y chromosomes (XY). This means that females can produce only one type of gamete carrying the X chromosome, while males can produce two types of gametes carrying either the X or Y chromosome.
04

Comparison of Protenor and Lygaeus Modes of Sex Determination

Here is a comparison between both modes: - Protenor Mode: - Female is heterogametic (ZW) - Male is homogametic (ZZ) - Lygaeus Mode: - Female is homogametic (XX) - Male is heterogametic (XY) Remember that the main difference between the modes lies in the gender that is heterogametic. In the Protenor mode, the female is heterogametic with ZW chromosomes, while in the Lygaeus mode, the male is heterogametic with XY chromosomes.

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Most popular questions from this chapter

Can the Lyon hypothesis be tested in a human female who is homozygous for one allele of the X-linked G6PD gene? Why, or why not?

What does the apparent need for dosage compensation mechanisms suggest about the expression of genetic information in normal diploid individuals?

An insect species is discovered in which the heterogametic sex is unknown. An X-linked recessive mutation for reduced wing (rw) is discovered. Contrast the \(F_{1}\) and \(F_{2}\) generations from a cross between a female with reduced wings and a male with normalsized wings when (a) the female is the heterogametic sex. (b) the male is the heterogametic sex.

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?

The genes encoding the red-and green-color-detecting proteins of the human eye are located next to one another on the X chromosome and probably evolved from a common ancestral pigment gene. The two proteins demonstrate 76 percent homology in their amino acid sequences. A normal-visioned woman with both genes on each of her two X chromosomes has a redcolor-blind son who was shown to have one copy of the greendetecting gene and no copies of the red-detecting gene. Devise an explanation for these observations at the chromosomal level (involving meiosis).
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