Part 3: Chromosome Theory of Inheritance & Sex Determination (25 MCQs)
Part 3: Chromosome Theory of Inheritance & Sex Determination (25 MCQs)
Q51. Chromosome theory of inheritance was proposed by:
a) Mendel
b) Sutton and Boveri
c) Morgan
d) Watson and Crick
Answer: b
- b) Correct: Sutton and Boveri (1902–03) proposed that genes are present on chromosomes.
- a) Mendel → laws of inheritance.
- c) Morgan → linkage and crossing over.
- d) Watson & Crick → DNA structure.
Q52. Which statement correctly explains the chromosome theory of inheritance?
a) Traits are inherited through proteins
b) Genes are located on chromosomes
c) Genes and chromosomes are unrelated
d) Genes are inherited only through cytoplasm
Answer: b
- b) Correct: Chromosome theory states that genes are carried on chromosomes.
- a, c, d) Wrong.
Q53. Sutton’s work on grasshopper meiosis showed:
a) Independent assortment of chromosomes
b) Equal contribution of maternal and paternal chromosomes
c) Pairing of homologous chromosomes
d) All of the above
Answer: d
- d) Correct: Sutton showed homologous chromosome pairing, segregation, and equal parental contribution.
Q54. Who proved that genes are located on chromosomes using Drosophila?
a) Sutton
b) Boveri
c) Morgan
d) Mendel
Answer: c
- c) Correct: T.H. Morgan’s Drosophila experiments proved genes are located on chromosomes.
Q55. A gene is best defined as:
a) A segment of RNA
b) A unit of heredity located on chromosome
c) A protein molecule
d) A type of cytoplasm
Answer: b
- b) Correct: Gene = unit of inheritance, DNA segment on chromosome.
- a, c, d) Incorrect.
Q56. Genes are located on:
a) Centromeres
b) Chromosomes
c) Ribosomes
d) Centrosomes
Answer: b
- b) Correct: Genes are DNA sequences present on chromosomes.
- a, c, d) Incorrect.
Q57. Which feature supports the chromosome theory of inheritance?
a) Genes and chromosomes both occur in pairs
b) Both segregate during gamete formation
c) Both assort independently
d) All of the above
Answer: d
- d) Correct: Chromosome behavior parallels gene behavior in all respects.
Q58. In humans, sex is determined by:
a) Number of autosomes
b) Number of sex chromosomes
c) Mitochondrial DNA
d) Hormones
Answer: b
- b) Correct: Sex in humans is determined by XX (female) and XY (male) sex chromosomes.
- a, c, d) Do not determine sex genetically.
Q59. A human female produces gametes with:
a) All X chromosomes
b) All Y chromosomes
c) Half X, half Y
d) No chromosomes
Answer: a
- a) Correct: Females are XX → produce gametes with only X chromosomes.
- c) Applies to males (produce X and Y gametes).
Q60. Which gamete decides the sex of the child in humans?
a) Male gamete
b) Female gamete
c) Both equally
d) None
Answer: a
- a) Correct: Male gamete (sperm) contributes X or Y → decides sex.
- b) Wrong: female contributes only X.
Q61. Sex chromosomes in male humans are:
a) XX
b) XY
c) ZZ
d) XO
Answer: b
- b) Correct: Human males = XY.
- a) Female humans = XX.
- c, d) Found in other organisms.
Q62. In birds, males are:
a) Homogametic (ZZ)
b) Heterogametic (ZW)
c) XO
d) XY
Answer: a
- a) Correct: Male birds = ZZ (homogametic).
- b) Female birds = ZW.
Q63. In birds, females are:
a) XX
b) XY
c) ZZ
d) ZW
Answer: d
- d) Correct: Female birds = ZW (heterogametic).
Q64. In honey bee sex determination, males (drones) are:
a) Haploid
b) Diploid
c) Triploid
d) Tetraploid
Answer: a
- a) Correct: Males (drones) arise from unfertilized eggs (haploid) by parthenogenesis.
Q65. In honey bees, females (workers and queen) are:
a) Haploid
b) Diploid
c) Triploid
d) Polyploid
Answer: b
- b) Correct: Female honey bees develop from fertilized eggs (diploid).
Q66. The mechanism of sex determination in honey bees is called:
a) XO type
b) XY type
c) ZW type
d) Haplodiploid type
Answer: d
- d) Correct: Honey bee → haplodiploid mechanism.
Q67. Which of the following is true for humans?
a) Male is homogametic, female heterogametic
b) Male is heterogametic, female homogametic
c) Both homogametic
d) Both heterogametic
Answer: b
- b) Correct: Humans → Male = XY (heterogametic), Female = XX (homogametic).
Q68. Which statement about chromosomes is wrong?
a) Chromosomes carry genes
b) Genes are located linearly on chromosomes
c) Chromosomes are only present during mitosis
d) Chromosomes occur in pairs in diploid organisms
Answer: c
- c) Correct: Chromosomes exist throughout the cell cycle, though condensed only during division.
Q69. Genes that are present at the same position on homologous chromosomes are called:
a) Alleles
b) Homologues
c) Loci
d) Chromatids
Answer: a
- a) Correct: Alternative forms of a gene = alleles, located at same locus.
Q70. The physical location of a gene on a chromosome is called:
a) Codon
b) Locus
c) Allele
d) Centromere
Answer: b
- b) Correct: Gene’s specific address = locus.
Q71. In the ZW system of sex determination, the heterogametic sex is:
a) Male
b) Female
c) Both
d) Neither
Answer: b
- b) Correct: Female birds = ZW (heterogametic).
Q72. In humans, the total number of autosomes is:
a) 22
b) 44
c) 2
d) 23
Answer: b
- b) Correct: 44 autosomes (22 pairs).
- a, c, d) Wrong counts.
Q73. Who gave experimental proof for linkage between genes?
a) Mendel
b) Sutton
c) Morgan
d) Watson
Answer: c
- c) Correct: T.H. Morgan (Drosophila) → linkage of genes on chromosomes.
Q74. In humans, sex chromosome complement of Turner’s syndrome individual is:
a) XXY
b) XO
c) XXX
d) XY
Answer: b
- b) Correct: Turner’s = XO (monosomy).
Q75. Which type of sex determination system is seen in grasshoppers?
a) XY
b) XO
c) ZW
d) Haplodiploid
Answer: b
- b) Correct: Grasshoppers → XO system (male = XO, female = XX).
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