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Questions and Answers
In genic sex-determination systems, what is the key factor in determining sex?
In genic sex-determination systems, what is the key factor in determining sex?
- The genotype at particular gene loci. (correct)
- The presence of specific sex chromosomes.
- The temperature of incubation during embryonic development.
- The position of the organism in a stack, like in the slipper limpet.
What is the sex chromosome complement of a male Drosophila melanogaster?
What is the sex chromosome complement of a male Drosophila melanogaster?
- XX
- XO
- YY
- XY (correct)
What is the X:A ratio in a Drosophila melanogaster with the sex chromosome complement XXY?
What is the X:A ratio in a Drosophila melanogaster with the sex chromosome complement XXY?
- 1.5
- 2.0
- 0.5
- 1.0 (correct)
What does the X:A ratio of 0.33 in Drosophila melanogaster produce?
What does the X:A ratio of 0.33 in Drosophila melanogaster produce?
What is the sex-determining mechanism in humans?
What is the sex-determining mechanism in humans?
Which of the following is NOT a characteristic of organisms with environmental sex-determination systems?
Which of the following is NOT a characteristic of organisms with environmental sex-determination systems?
What is the sex chromosome complement in a female bird?
What is the sex chromosome complement in a female bird?
Which syndrome involves the sex chromosome complement XO in humans?
Which syndrome involves the sex chromosome complement XO in humans?
In the context of sex determination in Drosophila melanogaster, what is the significance of the 'A' in the X:A ratio?
In the context of sex determination in Drosophila melanogaster, what is the significance of the 'A' in the X:A ratio?
Which of the following is a key difference between chromosomal and genic sex determination systems?
Which of the following is a key difference between chromosomal and genic sex determination systems?
What is the primary determinant of maleness in humans?
What is the primary determinant of maleness in humans?
Which condition is characterized by individuals having XY sex chromosomes but presenting with female external characteristics?
Which condition is characterized by individuals having XY sex chromosomes but presenting with female external characteristics?
What happens in the absence of a Y chromosome in human development?
What happens in the absence of a Y chromosome in human development?
What is the role of the SRY gene during embryonic development?
What is the role of the SRY gene during embryonic development?
Why do extra X chromosomes upset normal development in humans?
Why do extra X chromosomes upset normal development in humans?
What defines a dioecious species?
What defines a dioecious species?
In the XX-XO sex-determining system, what is the sex chromosome composition of male grasshoppers?
In the XX-XO sex-determining system, what is the sex chromosome composition of male grasshoppers?
What is the primary role of sex chromosomes in chromosomal sex-determining systems?
What is the primary role of sex chromosomes in chromosomal sex-determining systems?
Which of the following statements is true about the chromosomal sex-determining system XX-XY?
Which of the following statements is true about the chromosomal sex-determining system XX-XY?
What does the term 'heterogametic sex' refer to in the XX-XY system?
What does the term 'heterogametic sex' refer to in the XX-XY system?
In the XX-XY system, what is the composition of gametes produced by females?
In the XX-XY system, what is the composition of gametes produced by females?
What does the Lyon hypothesis explain?
What does the Lyon hypothesis explain?
What does the term 'homozygous' refer to in sex-linked inheritance?
What does the term 'homozygous' refer to in sex-linked inheritance?
Flashcards
Sex Determination
Sex Determination
The biological mechanism that defines an organism's sex, such as male or female.
Monoecious Species
Monoecious Species
Organisms that possess both male and female reproductive structures.
Dioecious Species
Dioecious Species
Organisms that have distinct male and female individuals.
Chromosomal Sex-Determining Systems
Chromosomal Sex-Determining Systems
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XX-XY System
XX-XY System
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XX-XO System
XX-XO System
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Homogametic Sex
Homogametic Sex
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Heterogametic Sex
Heterogametic Sex
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Y Chromosome Role
Y Chromosome Role
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SRY Gene
SRY Gene
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Androgen-Insensitivity Syndrome
Androgen-Insensitivity Syndrome
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Extra X Chromosomes
Extra X Chromosomes
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Fertility Genes Location
Fertility Genes Location
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ZW/ZZ system
ZW/ZZ system
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Genic sex determination
Genic sex determination
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Environmental sex determination
Environmental sex determination
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Sequential hermaphroditism
Sequential hermaphroditism
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Drosophila sex determination
Drosophila sex determination
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X:A ratio
X:A ratio
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Turner syndrome
Turner syndrome
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Klinefelter syndrome
Klinefelter syndrome
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Poly-X females
Poly-X females
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Aromatase enzyme's role
Aromatase enzyme's role
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Study Notes
Sex Determination and Sex-linked Characteristics
- Sex determination systems are mechanisms that dictate the sex of an organism.
- In most organisms, there are two sexes: male and female.
- Monoecious species have both male and female reproductive structures in a single organism.
- Dioecious species have either male or female reproductive structures in a single organism.
- Dioecious species exhibit various sex determination systems, including chromosomal, genic, and environmental.
Chromosomal Sex-Determining Systems
- Sexual phenotype is determined by sex chromosomes, which differ in number and/or type between males and females.
- Non-sex chromosomes are called autosomes.
- Examples include XX-XO, XX-XY, and ZZ-ZW systems.
XX-XO System
- Grasshoppers use this system
- Females have two X chromosomes (XX).
- Males have one X chromosome (XO).
- The absence of the second X chromosome is denoted by 'O'.
- Females are homogametic (all eggs carry an X chromosome).
- Males are heterogametic (half of the sperm carry X, the other half have no sex chromosome).
XX-XY System
- Mammals, some insects, and reptiles use this system.
- Females have two X chromosomes (XX).
- Males have one X and one Y chromosome (XY)
- Females are homogametic (all eggs carry X chromosome).
- Males are heterogametic (half of the sperm carry X, the other half carry Y).
ZZ-ZW System
- Some species like birds, snakes, and butterflies have this system.
- Females have one Z and one W chromosome (ZW), which is the heterogametic sex.
- Males have two Z chromosomes (ZZ), which is the homogametic sex.
Genic Sex-Determining Systems
- In some organisms, sex is determined by genes, not by sex chromosomes.
- No difference in primary chromosomes between males and females is visible.
- The phenotype (genotype) is determined by sex-determining genes at particular genetic loci.
- Plants, fungi, protozoans, and fish employ genic sex determination as part of their sexual development process.
Environmental Sex-Determining Systems
- Temperature of incubation is a factor determining the sex in turtles.
- Cooler temperatures lead to more male turtles, while warmer temperatures lead to more female turtles.
- Some other species exhibit sequential hermaphroditism (e.g., Slipper limpets).
Sex Determination in Drosophila melanogaster
- Diploid: 8 chromosomes (3 pairs of autosomes, 2 sex chromosomes).
- Haploid flies have two haploid sets of autosomes and two sex chromosomes.
- Sex chromosomes are XX for females and XY for males.
- It is not the presence of a Y chromosome that determines the sex but an X:A ratio.
- The X:A ratio is the number of X chromosomes divided by the number of haploid autosomes.
Sex Determination in Humans
- XX-XY system: Y chromosome determines maleness.
- Role of sex chromosomes understood from abnormal numbers of sex chromosomes in humans.
- Examples of syndromes: Turner syndrome (XO), Klinefelter syndrome (XXY), and Poly-X females (XXX).
- The Y chromosome contains a Sex Determining Region Y (SRY) gene.
- SRY gene product causes differentiation of neutral gonads into testes early in embryonic development.
- Androgen insensitivity syndrome: XY females due to defective androgen receptor and can produce testosterone but cannot bind to the androgen receptors for male characteristics.
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Description
Explore the fascinating world of sex determination systems and characteristics through this quiz. Gain insights into monoecious and dioecious species, as well as various chromosomal systems like XX-XO, XX-XY, and more. Test your understanding of these biological concepts today!
