18 Questions
What is the primary role of the Y chromosome in mammals?
Determining the male sex
What is the difference between XO mammals and XO Drosophila?
XO mammals are females, while XO Drosophila are sterile males
What determines the sex of a Drosophila fruit fly?
The balance of female determinants on the X chromosome and male determinants on the autosomes
What is the result of a 1X:2A ratio in a Drosophila fruit fly?
The fly is male
What is the function of the Y chromosome in Drosophila?
It contains genes active in forming sperm in adults
What is a metafemale or superfemale in Drosophila?
A low viability fruit fly with a female phenotype, having a ratio of X chromosomes to sets of autosomes exceeding 1.0
What is the significance of the 2X:2A ratio in Drosophila?
It results in a female fly
How do the sex-determining mechanisms in mammals and Drosophila differ?
Mammals rely on the Y chromosome, while Drosophila relies on the X-to-autosome ratio
What is the result of an imbalance in the X-to-autosome ratio in Drosophila?
Impaired development and often failure to emerge from the pupae
In Drosophila, what is the significance of the autosomes in determining sex?
Autosomes contain male determinants that balance with female determinants on the X chromosome to determine sex.
How does the sex determination mechanism in Drosophila respond to changes in the X-to-autosome ratio?
Changes in the X-to-autosome ratio affect the balance of female and male determinants, leading to changes in the resulting sex.
What is the difference between the role of the Y chromosome in mammals and in Drosophila?
In mammals, the Y chromosome plays a pivotal role in determining the male sex, whereas in Drosophila, the Y chromosome is not involved in determining sex and instead contains genes active in forming sperm.
How does the development of a metafemale or superfemale in Drosophila differ from normal development?
The development of a metafemale or superfemale is impaired due to the disproportionate ratio of X chromosomes to autosomes, often leading to failure to emerge from the pupae.
What is the result of having only one X chromosome in a diploid cell in Drosophila?
The fly is male.
How does the sex determination mechanism in Drosophila compare to that in other insects?
The sex determination mechanism in Drosophila is similar to that in other insects, but different from that in mammals.
What is the role of the X chromosome in determining sex in Drosophila?
The X chromosome contains female determinants that balance with male determinants on the autosomes to determine sex.
How does the presence of two X chromosomes in a diploid cell affect the development of a Drosophila individual?
The presence of two X chromosomes in a diploid cell results in a female individual.
What is the significance of the 1X:2A ratio in understanding the sex determination mechanism in Drosophila?
The 1X:2A ratio demonstrates the importance of the balance between female and male determinants in determining sex.
Study Notes
Sex Determination in Drosophila and Mammals
- Sex determination mechanisms in mammals and insects, such as Drosophila, are very different.
Mammals
- In mammals, the Y chromosome plays a crucial role in determining the male sex.
- XO mammals are females with ovaries, a uterus, and oviducts, but usually very few or no ova.
Drosophila
- Sex determination in Drosophila is achieved by a balance of female determinants on the X chromosome and male determinants on the autosomes.
- Normally, flies have either one or two X chromosomes and two sets of autosomes.
- A fly with one X chromosome in a diploid cell (1X:2A) is male.
- A fly with two X chromosomes in a diploid cell (2X:2A) is female.
- XO Drosophila are sterile males.
- The Y chromosome is not involved in determining sex in Drosophila, instead containing genes active in forming sperm in adults.
X-to-Autosome Ratios
- Different X-to-autosome ratios result in varying sexes:
- 1X:2A = male
- 2X:2A = female
- X:A ratio exceeding 1.0 = metafemale (or superfemale), a low viability Drosophila fruit fly with a female phenotype, often resulting in impaired development and failure to emerge from the pupae.
Understand the differences in sex determination mechanisms between mammals and fruit flies. Learn how chromosomes determine the sex of an individual in Drosophila and how it varies from mammals. Test your knowledge of genetics and sex determination in this quiz!
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