/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 3 Describe the XX-XO system of sex... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 4: Problem 3

Describe the XX-XO system of sex determination. In this system, which is the heterogametic sex, and which is the homogametic sex?

Short Answer

Expert verified
In the XX-XO system, males (XO) are heterogametic, and females (XX) are homogametic.

Step by step solution

01

Understand the XX-XO System

The XX-XO system of sex determination is a mechanism found in some insects like grasshoppers and certain other organisms. In this system, the females have two sex chromosomes that are of the same type: XX. This means they are the homogametic sex. Males, on the other hand, have only one sex chromosome: X, and lack the second sex chromosome entirely, which is represented as XO. This makes males the heterogametic sex.
02

Identify the Heterogametic Sex

In the context of the XX-XO system, the heterogametic sex is the one with two different sex chromosomes. Since males have one X chromosome and the absence of a second sex chromosome (represented as O), males are considered the heterogametic sex.
03

Identify the Homogametic Sex

The homogametic sex has two identical sex chromosomes. In the XX-XO system, females have two X chromosomes (XX), making them the homogametic sex.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Heterogametic Sex
In the realm of genetics and sex determination, the term "heterogametic sex" is used to describe the sex that possesses two different types of sex chromosomes. In the XX-XO system, typically found in some insects, males fall into this category. This is because they have one X chromosome and lack a second sex chromosome, represented symbolically as "O." In other sex determination systems, such as XY, males are also considered heterogametic, but with a different configuration: one X and one Y chromosome. The variations in gametes, primarily due to the presence of a single X chromosome and an unpaired chromosome (O in this case), define the heterogametic nature of males in the XX-XO system. This combination means males can pass on only an X chromosome or no additional sex chromosome at all, leading to unique gametes and ultimately playing a pivotal role in the sex determination of their offspring.
Homogametic Sex
The term "homogametic sex" refers to the gender having two similar sex chromosomes. In the XX-XO system of sex determination, females are the homogametic sex. They possess two of the same type of sex chromosome, which are the X chromosomes, denoted as XX. This similarity in sex chromosomes means that females produce gametes that all contain the same type of sex chromosome. Thus, every egg from a female in this system carries an X chromosome. Such a configuration ensures that the offspring will receive an X chromosome from the mother regardless of the type of gamete contributed by the father, contributing to the predictability and stability of genotypic inheritance in such species.
Insects
Insects exhibit a fascinating variety of mechanisms for sex determination, with the XX-XO system being one of them. This system is primarily observed in Orthopteran insects, like grasshoppers, where it plays a crucial role in determining the sex of an individual. A key feature of insects utilizing this system is the absence of a second sex chromosome in males, hence the "O," which signifies the lack of a homologous partner to the X chromosome. This system's simplicity supports quick adaptations in insect populations, as relatively minor genetic shifts can alter sex ratios, offering evolutionary advantages in fluctuating environments. Such adaptations can directly affect reproductive strategies and, consequently, population dynamics. Studying these insects' sex determination mechanisms reveals practical insights into evolutionary biology, paving the way for understanding more complex systems in other species.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Miniature wings in Drosophila result from an X-linked allele \(\left(\mathrm{X}^{m}\right)\) that is recessive to the allele for long wings \(\left(\mathrm{X}^{+}\right) .\) Sepia eyes are produced by an autosomal allele (s) that is recessive to an allele for red eyes \(\left(s^{+}\right)\). a. A female fly that has miniature wings and sepia eyes is crossed with a male that has normal wings and is homozygous for red eyes. The \(\mathrm{F}_{1}\) flies are intercrossed to produce the \(\mathrm{F}_{2}\). Give the phenotypes, as well as their expected proportions, of the \(\mathrm{F}_{1}\) and \(\mathrm{F}_{2}\) flies. b. A female fly that is homozygous for normal wings and has sepia eyes is crossed with a male that has miniature wings and is homozygous for red eyes. The \(\mathrm{F}_{1}\) flies are intercrossed to produce the \(\mathrm{F}_{2}\). Give the phenotypes, as well as their expected proportions, of the \(\mathrm{F}_{1}\) and \(\mathrm{F}_{2}\) flies.

The following two genotypes are crossed: \(A a B b C c\) \(\mathrm{X}^{+} \mathrm{X}^{r} \times A a B B \mathrm{cc} \mathrm{X}^{+} \mathrm{Y},\) where \(a, b,\) and \(c\) represent alleles of autosomal genes, and \(\mathrm{X}^{+}\) and \(\mathrm{X}^{r}\) represent X-linked alleles in an organism with XX-XY sex determination. What is the probability of obtaining genotype \(a a B b C c X^{+} X^{+}\) in the progeny? See Chapter 3 for a review of autosomal inheritance.

Joe has classic hemophilia, an X-linked recessive disease. Could Joe have inherited the gene for this disease from the following people? $$\begin{array}{cc}&\text{Yes} &&& \text{No} \\ \text{a. His mother's mother} & \underline{} &&&\underline{}\\\ \text{b. His mother's father} & \underline{} &&&\underline{}\\\ \text{c. His father's mother} & \underline{} &&&\underline{}\\\ \text{d. His father's father} & \underline{} &&&\underline{} \end{array}$$

How does sex determination in the XX-XY system differ from sex determination in the ZZ-ZW system?

\(\mathrm{Xg}\) is an antigen found on red blood cells. This antigen is caused by an X-linked allele \(\left(X^{a}\right)\) that is dominant over an allele for the absence of the antigen \(\left(\mathrm{X}^{-}\right) .\) The inheritance of these \(\mathrm{X}\) -linked alleles was studied in children with chromosome abnormalities to determine where nondisjunction of the sex chromosomes took place. For each type of mating in parts \(a\) through \(d\), indicate whether nondisjunction took place in the mother or in the father and, if possible, whether it took place in meiosis I or meiosis II (assume no crossing over). a. \(X^{a} Y \times X^{-} X^{-} \rightarrow X^{a}\) (Turner syndrome) b. \(X^{a} Y \times X^{a} X^{-} \rightarrow X^{-}\) (Turner syndrome) c. \(\mathrm{X}^{a} \mathrm{Y} \times \mathrm{X}^{-} \mathrm{X}^{-} \rightarrow \mathrm{X}^{a} \mathrm{X}^{-} \mathrm{Y}\) (Klinefelter syndrome) d. \(X^{a} Y \times X^{a} X^{-} \rightarrow X^{-} X^{-} Y\) (Klinefelter syndrome)
See all solutions

Recommended explanations on Biology Textbooks

Genetic Information

Read Explanation

Organ Systems

Read Explanation

Reproduction

Read Explanation

Cell Cycle

Read Explanation

Microbiology

Read Explanation

Biological Processes

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.