Sex Determination Practice Questions
20 free Sex Determination practice questions for the Zoology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which sex-determination system is found in humans?
- A XO system
- B ZW system
- C Haplodiploidy
- D XY system
Correct answer: XY system
Humans follow the XY system where males are XY and females are XX. The presence of the Y chromosome determines male development.
In the XY system, which sex is heterogametic?
- A Male
- B Female
- C Both
- D Neither
Correct answer: Male
In the XY system, males are heterogametic because they produce two types of gametes (X and Y). Females produce only X-bearing gametes.
Which sex-determination system is seen in birds?
- A XY system
- B XO system
- C Haplodiploidy
- D ZW system
Correct answer: ZW system
Birds use the ZW system where females are ZW and males are ZZ. The female determines the sex of the offspring.
In the ZW system, which sex is heterogametic?
- A Female
- B Male
- C Both sexes
- D Neither sex
Correct answer: Female
In the ZW system, females are heterogametic because they produce two types of gametes (Z and W). Males are homogametic (ZZ).
What is the chromosomal composition of males in the XO system?
- A XO
- B XX
- C XY
- D ZZ
Correct answer: XO
In the XO system, males have only one X chromosome (XO). Females have two X chromosomes (XX).
Which organism commonly exhibits the XO type of sex determination?
- A Human beings
- B Some birds
- C Some bees
- D Grasshoppers
Correct answer: Grasshoppers
Grasshoppers and some insects follow the XO system. Males have one X chromosome, while females have two.
What determines sex in the haplodiploidy system?
- A Number of chromosome sets
- B Presence of Y chromosome
- C Environmental temperature
- D Gene mutation
Correct answer: Number of chromosome sets
In haplodiploidy, sex is determined by the number of chromosome sets. Fertilized eggs become diploid females, and unfertilized eggs become haploid males.
Which group of animals shows haplodiploid sex determination?
- A Bees and ants
- B Most mammals
- C Most birds
- D Most reptiles
Correct answer: Bees and ants
Bees, ants, and wasps follow haplodiploidy. Males develop from unfertilized eggs, while females develop from fertilized eggs.
Which chromosome carries the SRY gene responsible for male development in humans?
- A Y chromosome
- B X chromosome
- C Autosome
- D Mitochondrial DNA
Correct answer: Y chromosome
The SRY gene is located on the Y chromosome and triggers male development. Its presence leads to the formation of testes.
What is homogametic sex?
- A Sex with identical sex chromosomes
- B Sex with two different sex chromosomes
- C Sex determined by environment
- D Sex without chromosomes
Correct answer: Sex with identical sex chromosomes
Homogametic sex has identical sex chromosomes, such as XX in females or ZZ in males. They produce only one type of gamete regarding sex chromosomes.
Which system involves environmental factors influencing sex determination?
- A XY-based system
- B ZW-based system
- C XO system
- D TSD system
Correct answer: TSD system
TSD (temperature-dependent sex determination) means environmental temperature during development determines sex, as seen in many reptiles such as turtles.
In reptiles with temperature-dependent sex determination, sex is influenced by:
- A Chromosome number
- B Gene mutation
- C Incubation temperature
- D Genetic inheritance pattern
Correct answer: Incubation temperature
In some reptiles, the temperature at which eggs are incubated determines the sex of offspring. This is an example of environmental sex determination.
Which chromosomal combination produces a female in humans?
- A XY
- B XO
- C XX
- D ZZ
Correct answer: XX
In humans, females have two X chromosomes (XX). This combination leads to female development in the absence of the Y chromosome.
What is the role of the Y chromosome in sex determination?
- A Suppresses gene expression
- B Carries mitochondrial DNA
- C Initiates male development
- D Determines female traits
Correct answer: Initiates male development
The Y chromosome contains the SRY gene, which initiates male development. Without it, the default development is female.
Which system results in males developing from unfertilized eggs?
- A Genic balance system
- B ZW system
- C XO system
- D Haplodiploidy
Correct answer: Haplodiploidy
In haplodiploidy, males develop from unfertilized eggs and are haploid. Females develop from fertilized eggs and are diploid.
Which of the following organisms uses the ZW system?
- A Humans
- B Grasshoppers
- C Birds
- D Bees
Correct answer: Birds
Birds use the ZW system where females are ZW and males are ZZ. This is opposite to the XY system in humans.
What is the chromosomal makeup of females in the ZW system?
- A ZZ
- B ZW
- C XX
- D XY
Correct answer: ZW
In the ZW system, females are ZW and are heterogametic. They produce two types of gametes (Z and W).
Which system is characterized by males having a single X chromosome and no second sex chromosome at all, while females are XX?
- A XY system
- B XO system
- C ZW system
- D Haplodiploidy
Correct answer: XO system
In the XO system, there is no Y chromosome. Males have only one X chromosome, while females have two.
Which factor primarily determines sex in the XY system?
- A Maternal genotype
- B Paternal contribution
- C Environmental temperature
- D Number of chromosomes
Correct answer: Paternal contribution
In the XY system, the father determines the sex by contributing either an X or Y chromosome. This decides whether the offspring is male or female.
Which statement is true about sex determination systems?
- A All animals use the XY system
- B Sex is always determined solely by genetics
- C Different organisms use different systems
- D Only mammals have sex chromosomes
Correct answer: Different organisms use different systems
Different organisms use a variety of sex determination systems such as XY, ZW, XO, and environmental systems. This diversity reflects evolutionary adaptations.