Concepts: Sex Determination in Humans and Other Organisms
1. Sex determination refers to
A. Development of reproductive organs
B. Determination of male or female sex
C. Formation of gametes
D. Secondary sexual characters
✅ Answer: B
📘 Explanation:
Sex determination is the process by which the sex of an organism is decided.
2. In humans, sex is determined at the time of
A. Birth
B. Puberty
C. Fertilization
D. Adolescence
✅ Answer: C
📘 Explanation:
Sex is determined at fertilization, depending on the sperm type.
3. Total number of chromosomes in humans is
A. 22
B. 44
C. 46
D. 48
✅ Answer: C
📘 Explanation:
Humans have 46 chromosomes (23 pairs).
4. How many pairs of autosomes are present in humans?
A. 21
B. 22
C. 23
D. 24
✅ Answer: B
📘 Explanation:
22 pairs are autosomes; 1 pair is sex chromosomes.
5. Which chromosomes determine sex in humans?
A. Autosomes
B. X chromosomes only
C. Y chromosomes only
D. Sex chromosomes
✅ Answer: D
📘 Explanation:
Sex chromosomes (X and Y) determine sex.
6. Human females are
A. Heterogametic
B. Homogametic
C. Haploid
D. Polyploid
✅ Answer: B
📘 Explanation:
Females (XX) produce only one type of gamete → homogametic.
7. Human males are
A. Homogametic
B. Diploid
C. Heterogametic
D. Haploid
✅ Answer: C
📘 Explanation:
Males (XY) produce X and Y sperms → heterogametic.
8. The chromosomal constitution of human male is
A. XX
B. XO
C. XY
D. YY
✅ Answer: C
📘 Explanation:
Human males have XY chromosomes.
9. The chromosomal constitution of human female is
A. XX
B. XY
C. XO
D. YY
✅ Answer: A
📘 Explanation:
Human females have XX chromosomes.
10. Which parent determines the sex of a child in humans?
A. Mother
B. Father
C. Both equally
D. Environment
✅ Answer: B
📘 Explanation:
Father produces X and Y sperms, so father determines sex.
11. Which chromosome carries the SRY gene?
A. X chromosome
B. Y chromosome
C. Autosome
D. Both X and Y
✅ Answer: B
📘 Explanation:
SRY gene is present on the Y chromosome.
12. The SRY gene is responsible for
A. Female development
B. Formation of ovaries
C. Male sex determination
D. Secondary sexual characters
✅ Answer: C
📘 Explanation:
SRY initiates testis formation.
13. Absence of SRY gene results in
A. Male development
B. Female development
C. Sterility
D. Mutation
✅ Answer: B
📘 Explanation:
Without SRY, default pathway is female development.
14. Which type of sex determination is found in humans?
A. XX–XO
B. ZZ–ZW
C. XX–XY
D. Haplodiploid
✅ Answer: C
📘 Explanation:
Humans follow XX–XY type.
15. XX–XO type of sex determination is seen in
A. Humans
B. Birds
C. Grasshopper
D. Honey bee
✅ Answer: C
📘 Explanation:
Grasshoppers show XX–XO system.
16. In XX–XO system, males are
A. XX
B. XY
C. XO
D. YY
✅ Answer: C
📘 Explanation:
Males have only one X chromosome.
17. ZZ–ZW type of sex determination is seen in
A. Humans
B. Grasshoppers
C. Birds
D. Mammals
✅ Answer: C
📘 Explanation:
Birds show ZZ–ZW system.
18. In birds, which sex is heterogametic?
A. Male
B. Female
C. Both
D. None
✅ Answer: B
📘 Explanation:
Females (ZW) are heterogametic.
19. Haplodiploid sex determination is seen in
A. Humans
B. Grasshopper
C. Frog
D. Honey bee
✅ Answer: D
📘 Explanation:
Honey bees show haplodiploid system.
20. In honey bees, males develop from
A. Fertilized eggs
B. Unfertilized eggs
C. Diploid eggs
D. Zygotes
✅ Answer: B
📘 Explanation:
Unfertilized eggs develop into haploid males.
21. Females in honey bees are
A. Haploid
B. Diploid
C. Triploid
D. Polyploid
✅ Answer: B
📘 Explanation:
Females develop from fertilized (diploid) eggs.
22. Which sex determination depends on environment?
A. Genetic
B. Chromosomal
C. Environmental
D. Haplodiploid
✅ Answer: C
📘 Explanation:
Some reptiles show environmental sex determination.
23. Temperature-dependent sex determination is seen in
A. Humans
B. Crocodiles
C. Birds
D. Insects
✅ Answer: B
📘 Explanation:
Crocodiles show temperature-based sex determination.
24. Which chromosome is larger in humans?
A. Y chromosome
B. X chromosome
C. Both same
D. Autosome
✅ Answer: B
📘 Explanation:
X chromosome is larger and gene-rich.
25. The Y chromosome is
A. Gene-rich
B. Larger than X
C. Smaller and gene-poor
D. Absent in males
✅ Answer: C
📘 Explanation:
Y chromosome is small with fewer genes.
26. Sex determination in humans is
A. Environmental
B. Hormonal
C. Genetic
D. Chemical
✅ Answer: C
📘 Explanation:
Sex determination is genetically controlled.
27. Which gamete decides sex of the offspring?
A. Ovum
B. Sperm
C. Zygote
D. Embryo
✅ Answer: B
📘 Explanation:
Sperm can be X or Y, deciding sex.
28. Which chromosome is always present in human ova?
A. X
B. Y
C. Z
D. W
✅ Answer: A
📘 Explanation:
Female produces only X-bearing ova.
29. In XX–XY system, male produces
A. Only X sperms
B. Only Y sperms
C. X and Y sperms
D. Z sperms
✅ Answer: C
📘 Explanation:
Males produce two types of sperms.
30. Sex chromosomes are also called
A. Autosomes
B. Allosomes
C. Chromatids
D. Centromeres
✅ Answer: B
📘 Explanation:
Sex chromosomes are called allosomes.
31. Z chromosome system is present in:
A. Mammals
B. Birds
C. Insects
D. Humans
Answer: B
32. Which is NOT genetic sex determination?
A. XY
B. ZW
C. Haplodiploidy
D. Temperature-based
Answer: D
33. In humans, sperm carrying Y produces:
A. Girl
B. Boy
C. Either
D. Non-viable
Answer: B
34. Barr body represents:
A. Active X
B. Inactive X
C. Y chromosome
D. Autosome
Answer: B
35. Number of Barr bodies in XX female:
A. 0
B. 1
C. 2
D. 3
Answer: B
Explanation: n – 1 rule.
36. Barr bodies in XXY male:
A. 0
B. 1
C. 2
D. 3
Answer: B
37. Barr bodies in XO female:
A. 0
B. 1
C. 2
D. 3
Answer: A
38. Sex chromosomes are also called:
A. Autosomes
B. Allosomes
C. Chromatids
D. Centromeres
Answer: B
39. Autosomes in humans:
A. 22 pairs
B. 23 pairs
C. 21 pairs
D. 24 pairs
Answer: A
40. Sex chromosomes in humans:
A. 1 pair
B. 2 pairs
C. 22 pairs
D. 23 pairs
Answer: A
41. Male grasshopper gametes:
A. All X
B. X or O
C. All O
D. XY
Answer: B
42. Female grasshopper gametes:
A. X only
B. O only
C. X or O
D. XY
Answer: A
43. Which shows male heterogamety?
A. Birds
B. Humans
C. Butterflies
D. Hens
Answer: B
44. Which shows female heterogamety?
A. Humans
B. Grasshoppers
C. Birds
D. Drosophila
Answer: C
45. Haploid males occur in:
A. Humans
B. Honeybees
C. Birds
D. Frogs
Answer: B
46. Diploid males (abnormal) may occur due to:
A. Fertilization failure
B. Genetic error
C. Temperature
D. Mutation
Answer: B
47. Which chromosome pairing ensures proper segregation?
A. Autosomes
B. Pseudoautosomal regions
C. Centromeres
D. Telomeres
Answer: B
48. Primary sex determination refers to:
A. Development of genitalia
B. Chromosomal sex
C. Hormonal control
D. Puberty
Answer: B
49. Secondary sex determination involves:
A. Chromosomes
B. Hormones
C. Genes
D. DNA replication
Answer: B
50. Incorrect statement:
A. Human female is homogametic
B. Human male is heterogametic
C. Birds show XY system
D. Honeybee males are haploid
Answer: C
Explanation: Birds follow ZW, not XY.
